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diff --git a/old/65569-0.txt b/old/65569-0.txt deleted file mode 100644 index 85741b6..0000000 --- a/old/65569-0.txt +++ /dev/null @@ -1,9324 +0,0 @@ -The Project Gutenberg eBook of Histology of medicinal plants, by William -Mansfield - -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you -will have to check the laws of the country where you are located before -using this eBook. - -Title: Histology of medicinal plants - -Author: William Mansfield - -Release Date: June 8, 2021 [eBook #65569] - -Language: English - -Character set encoding: UTF-8 - -Produced by: Peter Becker, Susan Carr and the Online Distributed - Proofreading Team at https://www.pgdp.net (This file was - produced from images generously made available by The Internet - Archive) - -*** START OF THE PROJECT GUTENBERG EBOOK HISTOLOGY OF MEDICINAL PLANTS *** - - - - - HISTOLOGY OF - MEDICINAL PLANTS - - BY - - WILLIAM MANSFIELD, A.M., PHAR.D. - - - Professor of Histology and Pharmacognosy, College of - Pharmacy of the City of New York - Columbia University - - - TOTAL ISSUE, FOUR THOUSAND - - - NEW YORK - JOHN WILEY & SONS, INC. - LONDON: CHAPMAN & HALL, LIMITED - - - - - Copyright, 1916, by - WILLIAM MANSFIELD - - - - - PREFACE - - -The object of the book is to provide a practical scientific course in -vegetable histology for the use of teachers and students in schools -and colleges. - -The medicinal plants are studied in great detail because they -constitute one of the most important groups of economic plants. The -cells found in these plants are typical of the cells occurring in -the vegetable kingdom; therefore the book should prove a valuable -text-book for all students of histology. - -The book contains much that is new. In Part II, which is devoted -largely to the study of cells and cell contents, is a new scientific, -yet practical, classification of cells and cell contents. The author -believes that his classification of bast fibres and hairs will clear -up much of the confusion that students have experienced when studying -these structures. - -The book is replete with illustrations, all of which are from -original drawings made by the author. As most of these illustrations -are diagnostic of the plants in which they occur, they will prove -especially valuable as reference plates. - -The material of the book is the outgrowth of the experience of the -author in teaching histology at the College of Pharmacy of the -City of New York, Columbia University, and of years of practical -experience gained by examining powdered drugs in the laboratory of a -large importing and exporting wholesale drug house. - -The author is indebted to Ernest Leitz and Bausch & Lomb Optical -Company for the use of cuts of microscopic apparatus used in Part I -of the book. - -The author also desires to express his appreciation to Professor -Walter S. Cameron, who has rendered him much valuable aid. - - WILLIAM MANSFIELD. - - COLUMBIA UNIVERSITY, - September, 1916. - - - - - CONTENTS - - - PART I - - SIMPLE AND COMPOUND MICROSCOPES AND MICROSCOPIC - TECHNIC - - - CHAPTER I - - THE SIMPLE MICROSCOPES - - PAGE - - Simple microscopes, forms of 4 - - - CHAPTER II - - COMPOUND MICROSCOPES - - Compound microscopes, structure of 7 - Compound microscopes, mechanical parts of 7 - Compound microscopes, optical parts of 9 - Compound microscopes, forms of 12 - - - CHAPTER III - - MICROSCOPIC MEASUREMENTS - - Ocular micrometer 19 - Stage micrometer 19 - Mechanical stage 21 - Micrometer eye-pieces 21 - Camera lucida 22 - Drawing apparatus 23 - Microphotographic apparatus 24 - - - CHAPTER IV - - HOW TO USE THE MICROSCOPE - - Illumination 26 - Micro lamp 27 - Care of the microscope 28 - Preparation of specimens for cutting 28 - Paraffin imbedding oven 30 - Paraffin blocks 31 - Cutting sections 31 - Hand microtome 31 - Machine microtomes 32 - - - CHAPTER V - - REAGENTS - - Reagent set 39 - Measuring cylinder 40 - - - CHAPTER VI - - HOW TO MOUNT SPECIMENS - - Temporary mounts 41 - Permanent mounts 41 - Cover glasses 43 - Glass slides 44 - Forceps 45 - Needles 46 - Scissors 46 - Turntable 46 - Labeling 47 - Preservation of mounted specimens 48 - Slide box 48 - Slide tray 48 - Slide cabinet 49 - - - PART II - - TISSUES, CELLS AND CELL CONTENTS - - - CHAPTER I - - THE CELL - - Typical cell 53 - Changes in a cell undergoing division 55 - Origin of multicellular plants 57 - - - CHAPTER II - - THE EPIDERMIS AND PERIDERM - - Leaf epidermis 59 - Testa epidermis 63 - Plant hairs 66 - Forms of hairs 67 - Papillæ 67 - Unicellular hairs 69 - Multicellular hairs 72 - Periderm 80 - Cork periderm 80 - Stone cell periderm 85 - Parenchyma and stone cell periderm 85 - - - CHAPTER III - - MECHANICAL TISSUES - - Bast fibres 89 - Crystal bearing bast fibres 90 - Porous and striated bast fibres 92 - Porous and non-striated bast fibres 96 - Non-porous and striated bast fibres 96 - Non-porous and non-striated bast fibres 96 - Occurrence of bast fibres in powdered drugs 103 - Wood fibres 104 - Collenchyma cells 106 - Stone cells 109 - Endodermal cells 116 - Hypodermal cells 118 - - - CHAPTER IV - - ABSORPTION TISSUE - - Root hairs 121 - - - CHAPTER V - - CONDUCTING TISSUE - - Vessels and tracheids 126 - Annular vessels 127 - Spiral vessels 127 - Sclariform vessels 128 - Reticulate vessels 131 - Pitted vessels 131 - Pitted vessels with bordered pores 131 - Sieve tubes 136 - Sieve plate 138 - Medullary bundles, rays and cells 138 - Medullary ray bundle 139 - The medullary ray 139 - The medullary ray cell 141 - Structure of the medullary ray cells 142 - Arrangement of the medullary ray cells in the medullary ray 142 - Latex tubes 142 - Parenchyma 144 - Cortical parenchyma 147 - Pith parenchyma 147 - Leaf parenchyma 150 - Aquatic plant parenchyma 150 - Wood parenchyma 150 - Phloem parenchyma 150 - Palisade parenchyma 150 - - - CHAPTER VI - - AERATING TISSUE - - Water pores 151 - Stomata 151 - Relation of stomata to the surrounding cells 154 - Lenticels 157 - Intercellular spaces 158 - - - CHAPTER VII - - SYNTHETIC TISSUE - - Photosynthetic tissue 163 - Glandular tissue 164 - Glandular hairs 164 - Secretion cavities 166 - Schizogenous cavities 168 - Lysigenous cavities 168 - Schizo-lysigenous cavities 168 - - - CHAPTER VIII - - STORAGE TISSUE - - Storage cells 173 - Storage cavities 176 - Crystal cavities 176 - Mucilage cavities 176 - Latex cavities 176 - Oil cavity 178 - Glandular hairs as storage organs 178 - Storage walls 179 - - - CHAPTER IX - - CELL CONTENTS - - Chlorophyll 182 - Leucoplastids 183 - Starch grains 183 - Occurrence 184 - Outline 185 - Size 185 - Hilum 185 - Nature of hilum 188 - Inulin 194 - Mucilage 194 - Hesperidin 196 - Volatile oil 196 - Tannin 196 - Aleurone grains 197 - Structure of aleurone grains 197 - Form of aleurone grains 197 - Description of aleurone grains 198 - Tests for aleurone grains 198 - Crystals 200 - Micro-crystals 200 - Raphides 200 - Rosette crystals 202 - Solitary crystals 205 - Cystoliths 210 - Forms of cystoliths 210 - Tests for cystoliths 215 - - - PART III - - HISTOLOGY OF ROOTS, RHIZOMES, STEMS, BARKS, - WOODS, FLOWERS, FRUITS AND SEEDS - - - CHAPTER I - - ROOTS AND RHIZOMES - - Cross-section of pink root 219 - Cross-section of ruellia root 219 - Cross-section of spigelia rhizome 223 - Cross-section of ruellia rhizome 226 - Powdered pink root 227 - Powdered ruellia root 227 - - - CHAPTER II - - STEMS - - Herbaceous stems 233 - Cross-section, spigelia stem 233 - Ruellia stem 235 - Powdered horehound 237 - Powdered spurious horehound 237 - Insect flower stems 241 - - - CHAPTER III - - WOODY STEMS - - Buchu stem 242 - Mature buchu stem 242 - Powdered buchu stem 245 - - - CHAPTER IV - - BARKS - - White pine bark 248 - Powdered white pine bark 250 - - - CHAPTER V - - WOODS - - Cross-section quassia 254 - Radial-section quassia 254 - Tangential-section quassia 258 - - - CHAPTER VI - - LEAVES - - Klip buchu 260 - Powdered klip buchu 262 - Mountain laurel 264 - Trailing arbutus 264 - - - CHAPTER VII - - FLOWERS - - Pollen grains 270 - Non-spiny-walled pollen grains 273 - Spiny-walled pollen grains 273 - Stigma papillæ 274 - Powdered insect flowers 278 - Open insect flowers 280 - Powdered white daisies 282 - - - CHAPTER VIII - - FRUITS - - Celery fruit 285 - - - CHAPTER IX - - SEEDS - - Sweet almonds 289 - - - CHAPTER X - - ARRANGEMENT OF VASCULAR BUNDLES - - Types of fibro-vascular bundles 292 - Radial vascular bundles 292 - Concentric vascular bundles 295 - Collateral vascular bundles 295 - Bi-collateral vascular bundles 298 - Open collateral vascular bundles 298 - - - INDEX - - - - - TABLE OF ILLUSTRATIONS - - PAGE - FIG. 1. Tripod Magnifier 4 - FIG. 2. Watchmaker’s Loupe 4 - FIG. 3. Folding Magnifier 4 - FIG. 4. Reading Glass 4 - FIG. 5. Steinheil Aplanatic Lens 5 - FIG. 6. Dissecting Microscope 5 - FIG. 7. Compound Microscope of Robert Hooke 8 - FIG. 8. Compound Microscope 10 - FIG. 9. Abbé Condenser 11 - FIG. 10. 11 - FIG. 11. 11 - FIG. 12. Objectives 11 - FIG. 13. 12 - FIG. 14. 12 - FIG. 15. Eye-Pieces. 12 - FIG. 16. Pharmacognostic Microscope 12 - FIG. 17. Research Microscope 14 - FIG. 18. Special Research Microscope 14 - FIG. 19. Greenough Binocular Microscope 15 - FIG. 20. Polarization Microscope 16 - FIG. 21. Ocular Micrometer 19 - FIG. 22. Stage Micrometer 19 - FIG. 23. Micrometer Eye-Piece 20 - FIG. 24. Micrometer Eye-Piece 21 - FIG. 25. Mechanical Stage 22 - FIG. 26. Camera Lucida 22 - FIG. 27. Camera Lucida 22 - FIG. 28. Drawing Apparatus 23 - FIG. 29. Microphotographic Apparatus 24 - FIG. 30. Micro Lamp 27 - FIG. 31. Paraffin-embedding Oven 30 - FIG. 32. Paraffin Blocks 31 - FIG. 33. Hand Microtome 31 - FIG. 34. Hand Cylinder Microtome 34 - FIG. 35. Hand Table Microtome 34 - FIG. 36. Base Sledge Microtome 35 - FIG. 37. Minot Rotary Microtome 36 - FIG. 38. Reagent Set 39 - FIG. 39. Measuring Cylinder 40 - FIG. 40. Staining Dish 40 - FIG. 41. Round Cover Glass 44 - FIG. 42. Square Cover Glass 44 - FIG. 43. Rectangular Cover Glass 44 - FIG. 44. Glass Slide 44 - FIG. 45. Histological Forceps 45 - FIG. 46. Forceps 45 - FIG. 47. Sliding-pin Forceps 45 - FIG. 48. Dissecting Needle 46 - FIG. 49. Scissors 46 - FIG. 50. Scalpels 47 - FIG. 51. Turntable 47 - FIG. 52. Slide Box 48 - FIG. 53. Slide Tray 48 - FIG. 54. Slide Cabinet 49 - - PLATE 1 THE ONION ROOT 56 - PLATE 2 LEAF EPIDERMIS 60 - PLATE 3 LEAF EPIDERMIS 61 - PLATE 4 TESTA EPIDERMAL CELLS 64 - PLATE 5 TESTA CELLS 65 - PLATE 6 PAPILLÆ 68 - PLATE 7 UNICELLULAR SOLITARY HAIRS 70 - PLATE 8 CLUSTERED UNICELLULAR HAIRS 71 - PLATE 9 MULTICELLULAR UNISERIATE NON-BRANCHED HAIRS 73 - PLATE 10 MULTICELLULAR MULTISERIATE NON-BRANCHED HAIRS 75 - PLATE 11 MULTICELLULAR UNISERIATE BRANCHED HAIRS 76 - PLATE 12 NON-GLANDULAR MULTICELLULAR HAIRS 78 - PLATE 13 MULTICELLULAR MULTISERIATE BRANCHED HAIRS 79 - PLATE 14 MULTICELLULAR MULTISERIATE BRANCHED HAIRS 81 - PLATE 15 MULTICELLULAR MULTISERIATE BRANCHED HAIRS 82 - PLATE 16 PERIDERM OF CASCARA SAGRADA (_Rhamnus purshiana_, - D.C.) 84 - PLATE 17 MANDRAKE RHIZOME and WHITE CINNAMON 86 - PLATE 18 PERIDERM OF WHITE OAK (_Quercus alba_, L.) 87 - PLATE 19 CRYSTAL-BEARING FIBRES OF BARKS 91 - PLATE 20 CRYSTAL-BEARING FIBRES OF BARKS 93 - PLATE 21 CRYSTAL-BEARING FIBRES OF LEAVES 94 - PLATE 22 BRANCHED BAST FIBRES 95 - PLATE 23 POROUS AND STRIATED BAST FIBRES 97 - PLATE 24 POROUS AND NON-STRIATED BAST FIBRES 98 - PLATE 25 NON-POROUS AND STRIATED BAST FIBRES 99 - PLATE 26 NON-POROUS AND NON-STRIATED BAST FIBRES 101 - PLATE 27 GROUPS OF BAST FIBRES 102 - PLATE 28 WOOD FIBRES 105 - PLATE 29 CATNIP STEM and MOTHERWORT STEM 107 - PLATE 30 COLLENCHYMA CELLS 108 - PLATE 31 BRANCHED STONE CELLS 110 - PLATE 32 POROUS AND STRIATED STONE CELLS 113 - PLATE 33 POROUS AND NON-STRIATED STONE CELLS 114 - PLATE 34 CINNAMON, RUELLA ROOT, CASCARA and CINNAMON 115 - PLATE 35 CROSS-SECTIONS OF ENDODERMAL CELLS OF 117 - PLATE 36 LONGITUDINAL SECTIONS OF ENDODERMAL CELLS 119 - PLATE 37 HYPODERMAL CELLS 120 - PLATE 38 CROSS-SECTION OF SARSAPARILLA ROOT (_Smilax - officinalis_, Kunth) 123 - PLATE 39 ROOT HAIRS (Fragments) 124 - PLATE 40 ANNULAR AND SPIRAL VESSELS 129 - PLATE 41 SPIRAL VESSELS 130 - PLATE 42 SCLARIFORM VESSELS 132 - PLATE 43 RETICULATE VESSELS 133 - PLATE 44 PITTED VESSELS 134 - PLATE 45 VESSELS 135 - PLATE 46 SIEVE TUBE 137 - PLATE 47 RADIAL LONGITUDINAL SECTION OF WHITE SANDALWOOD - (_Santalum album_, L.) 140 - PLATE 48 KAVA-KAVA ROOT and WHITE PINE BARK 143 - PLATE 49 BLACK INDIAN HEMP and BLACK INDIAN HEMP ROOT 145 - PLATE 50 LATEX VESSELS 146 - PLATE 51 PARENCHYMA CELLS 148 - PLATE 52 GRINDELIA STEM (longitudinal) and GRINDELIA STEM - (cross-section) 149 - PLATE 53 ACONITE STEM and PEPPERMINT STEM 152 - PLATE 54 TYPES OF STOMA 153 - PLATE 55 LEAF EPIDERMI WITH STOMA 155 - PLATE 56 BELLADONNA LEAF, DEER TONGUE LEAF and WHITE PINE LEAF 156 - PLATE 57 ELDER BARK 159 - PLATE 58 INTERCELLULAR AIR SPACES 160 - PLATE 59 IRREGULAR INTERCELLULAR AIR SPACES 161 - PLATE 60 GLANDULAR HAIRS 165 - PLATE 61 STALKED GLANDULAR HAIRS 167 - PLATE 62 CALAMUS RHIZOME and WHITE PINE BARK 169 - PLATE 63 CANELLA ALBA BARK and KLIP BUCHU LEAF 170 - PLATE 64 BITTER ORANCE PEEL and WHITE PINE LEAF 171 - PLATE 65 CINNAMON, CALUMBA, PARENCHYMA, SARSAPARILLA, - LEPTANDRA, QUEBRACHO, BLACKBERRY 174 - PLATE 66 MUCILAGE AND RESIN 175 - PLATE 67 CROSS-SECTION OF SKUNK-CABBAGE LEAF (_Symplocarpus - fœtidus_, [L.] Nutt.) 177 - PLATE 68 RESERVE CELLULOSE 180 - PLATE 69 RESERVE CELLULOSE 181 - PLATE 70 STARCH 186 - PLATE 71 STARCH 187 - PLATE 72 STARCH 189 - PLATE 73 STARCH 190 - PLATE 74 STARCH 191 - PLATE 75 STARCH GRAINS 192 - PLATE 76 STARCH MASSES 193 - PLATE 77 INULIN (_Inula helenium_, L.) 195 - PLATE 77_a_ ALEURONE GRAINS 199 - PLATE 78 MICRO-CRYSTALS 201 - PLATE 79 RAPHIDES 203 - PLATE 80 ROSETTE CRYSTALS 204 - PLATE 81 INCLOSED ROSETTE CRYSTALS 206 - PLATE 82 SOLITARY CRYSTAL 207 - PLATE 83 SOLITARY CRYSTALS 208 - PLATE 84 SOLITARY CRYSTALS 209 - PLATE 85 SOLITARY CRYSTALS 211 - PLATE 86 SOLITARY CRYSTALS 212 - PLATE 87 ROSETTE CRYSTALS AND SOLITARY CRYSTALS OCCURRING IN 213 - PLATE 88 CYSTOLITHS 214 - PLATE 89 CROSS-SECTION OF ROOT OF SPIGELIA MARYLANDICA, L. 220 - PLATE 90 RUELLIA ROOT (_Ruellia ciliosa_, Pursh.). 222 - PLATE 91 CROSS-SECTION OF RHIZOME OF SPIGELIA MARYLANDICA, L. 224 - PLATE 92 CROSS-SECTION OF RHIZOME OF RUELLIA CILIOSA, Pursh. 225 - PLATE 93 POWDERED SPIGELIA MARYLANDICA, L. 228 - PLATE 94 POWDERED RUELLIA CILIOSA, Pursh. 229 - PLATE 95 CROSS-SECTION OF STEM OF SPIGELIA MARYLANDICA, L. 234 - PLATE 96 CROSS-SECTION OF STEM OF RUELLIA CILIOSA, Pursh. 236 - PLATE 97 POWDERED HOREHOUND (_Marrubium vulgare_, L). 238 - PLATE 98 SPURIOUS HOREHOUND (_Marrubium peregrinum_, L.) 239 - PLATE 99 POWDERED INSECT FLOWER STEMS (_Chrysanthemum - cinerariifolium_, [Trev.], Vis.) 240 - PLATE 100 CROSS-SECTION OF BUCHU STEMS (_Barosma betulina_ - [Berg.], Barth, and Wendl.) 243 - PLATE 101 BUCHU STEM and LEPTANDRA RHIZOME 244 - PLATE 102 POWDERED BUCHU STEMS (_Barosma betulina_ [Berg.], - Barth. and Wendl.). 246 - PLATE 103 CROSS-SECTION OF UNROSSED WHITE PINE BARK (_Pinus - strobus_, L.) 249 - PLATE 104 POWDERED WHITE PINE BARK (_Pinus strobus_, L.) 251 - PLATE 105 CROSS-SECTION OF QUASSIA WOOD (_Picræna excelsa_ - [Sw.], Lindl.) 255 - PLATE 106 TANGENTIAL SECTION OF QUASSIA WOOD (_Picræna - excelsa_ [Sw.], Lindl.) 256 - PLATE 107 RADIAL SECTION OF QUASSIA WOOD (_Picræna excelsa_ - [Sw.], Lindl.) 257 - PLATE 108 CROSS-SECTION OF KLIP BUCHU JUST OVER THE VEIN 261 - PLATE 109 POWDERED KLIP BUCHU 263 - PLATE 110 CROSS-SECTION MOUNTAIN LAUREL (_Kalmia latifolia_, - L.) 265 - PLATE 111 CROSS-SECTION TRAILING ARBUTUS LEAF (_Epigæa - repens_, L.) 266 - PLATE 112 POWDERED INSECT FLOWER LEAVES 268 - PLATE 113 SMOOTH-WALLED POLLEN GRAINS 271 - PLATE 114 SPINY WALLED POLLEN GRAINS 272 - PLATE 115 PAPILLÆ 275 - PLATE 116 PAPILLÆ OF STIGMAS 276 - PLATE 117 PAPILLÆ OF STIGMAS 277 - PLATE 118 POWDERED CLOSED INSECT FLOWER 279 - PLATE 119 POWDERED OPEN INSECT FLOWER 281 - PLATE 120 POWDERED WHITE DAISIES (_Chrysanthemum - leucanthemum_, L.) 283 - PLATE 121 CROSS-SECTION OF CELERY FRUIT (_Apium - graveolens_, L.) 286 - PLATE 121 CROSS-SECTION OF CELERY FRUIT (_Apium - graveolens_, L.) 286 - PLATE 123 CROSS-SECTION SWEET ALMOND SEED 290 - PLATE 124 CROSS-SECTION OF A RADIAL VASCULAR BUNDLE OF - SKUNK CABBAGE ROOT 293 - PLATE 125 CROSS-SECTION OF A PHLOEM-CENTRIC BUNDLE OF - CALAMUS RHIZOME (_Acorus calamus_, L.) 294 - PLATE 126 CROSS-SECTION OF A CLOSED COLLATERAL BUNDLE OF - MANDRAKE STEM (_Podophyllum peltatum_, L.) 286 - PLATE 127 BI-COLLATERAL BUNDLE OF PUMPKIN STEM (_Curcurbita - pepo_, L.) 297 - - - - - Part I - - SIMPLE AND COMPOUND MICROSCOPES AND MICROSCOPIC TECHNIC - - - - - CHAPTER I - - THE SIMPLE MICROSCOPES - - -The construction and use of the =simple microscope= (magnifiers) -undoubtedly date back to very early times. There is sufficient -evidence to prove that spheres of glass were used as burning spheres -and as magnifiers by people antedating the Greeks and Romans. - -The simple microscopes of to-day have a very wide range of -application and a corresponding variation in structure and in -appearance. - -Simple microscopes are used daily in classifying and studying crude -drugs, testing linen and other cloth, repairing watches, in reading, -and identifying insects. The more complex simple microscopes are used -in the dissection and classification of flowers. - -The =watchmaker’s loupe=, the =linen tester=, the =reading glass=, -the =engraver’s lens=, and the simplest folding magnifiers consist -of a double convex lens. Such a lens produces an erect, enlarged -image of the object viewed when the lens is placed so that the object -is within its focal distance. The focal distance of a lens varies -according to the curvature of the lens. The greater the curvature, -the shorter the focal distance and the greater the magnification. - -The more complicated simple microscope consists of two or more -lenses. The double and triple magnifiers consist of two and three -lenses respectively. - -When an object is viewed through three lenses, the magnification is -greater than when viewed through one or two lenses, but a smaller -part of the object is magnified. - - - FORMS OF SIMPLE MICROSCOPES - - - TRIPOD MAGNIFIER - -The =tripod magnifier= (Fig. 1) is a simple lens mounted on a -mechanical stand. The tripod is placed over the object and the focus -is obtained by means of a screw which raises or lowers the lens, -according to the degree it is magnified. - - - WATCHMAKER’S LOUPE - -The =watchmaker’s loupe= (Fig. 2) is a one-lens magnifier mounted on -an ebony or metallic tapering rim, which can be placed over the eye -and held in position by frowning or contracting the eyelid. - -[Illustration: FIG. 1.--Tripod Magnifier] - -[Illustration: FIG. 2.--Watchmaker’s Loupe] - - - FOLDING MAGNIFIER - -The =folding magnifier= (Fig. 3) of one or more lenses is mounted -in such a way that, when not in use, the lenses fold up like the -blade of a knife, and when so folded are effectively protected from -abrasion by the upper and lower surfaces of the folder. - -[Illustration: FIG. 3.--Folding Magnifier] - -[Illustration: FIG. 4.--Reading Glass] - - - READING GLASSES - -=Reading glasses= (Fig. 4) are large simple magnifiers, often six -inches in diameter. The lens is encircled with a metal band and -provided with a handle. - -[Illustration: FIG. 5.--Steinheil Aplanatic Lens] - - - STEINHEIL APLANATIC LENSES - -=Steinheil aplanatic lenses= (Fig. 5) consist of three or four -lenses cemented together. The combination is such that the field is -large, flat, and achromatic. These lenses are suitable for field, -dissecting, and pocket use. When such lenses are placed in simple -holders, they make good dissecting microscopes. - -[Illustration: FIG. 6.--Dissecting Microscope] - - - DISSECTING MICROSCOPE - -The =dissecting microscope= (Fig. 6) consists of a Steinheil lens -and an elaborate stand, a firm base, a pillar, a rack and pinion, -a glass stage, beneath which there is a groove for holding a metal -plate with one black and one white surface. The nature of the object -under observation determines whether a plate is used. When the plate -is used and when the object is studied by reflected light it is -sometimes desirable to use the black and sometimes the white surface. -The mirror, which has a concave and a plain surface, is used to -reflect the light on the glass stage when the object is studied by -transmitted light. The dissecting microscope magnifies objects up to -twenty diameters, or twenty times their real size. - - - - - CHAPTER II - - COMPOUND MICROSCOPES - - -The =compound microscope= has undergone wonderful changes since 1667, -the days of Robert Hooke. When we consider the crude construction -and the limitations of Robert Hooke’s microscope, we marvel at the -structural perfection and the unlimited possibilities of the modern -instrument. The advancement made in most sciences has followed the -gradual perfection of this instrument. - -The illustration of Robert Hooke’s microscope (Fig. 7) will convey -to the mind more eloquently than words the crudeness of the early -microscopes, especially when it is compared with the present-day -microscopes. - - - STRUCTURE OF THE COMPOUND MICROSCOPE - -The parts of the compound microscope (Fig. 8) may be grouped -into--first, the mechanical, and, secondly, into the optical parts. - - - THE MECHANICAL PARTS - -1. The =foot= is the basal part, the part which supports all the -other mechanical and optical parts. The foot should be heavy enough -to balance the other parts when they are inclined. Most modern -instruments have a three-parted or tripod-shaped base. - -2. The =pillar= is the vertical part of the microscope attached to -the base. The pillar is joined to the limb by a hinged joint. The -hinges make it possible to incline the microscope at any angle, thus -lowering its height. In this way, short, medium, and tall persons -can use the microscope with facility. The part of the pillar above -the hinge is called the _limb_. The limb may be either straight -or curved. The curved form is preferable, since it offers a more -suitable surface to grasp in transferring from box or shelf to the -desk, and _vice versa_. - -[Illustration: FIG. 7.--Compound Microscope of Robert Hooke] - -3. The =stage= is either stationary or movable, round or square, and -is attached to the limb just above the hinge. The upper surface is -made of a composition which is not easily attacked by moisture and -reagents. The centre of the stage is perforated by a circular opening. - -4. The =sub-stage= is attached below the stage and is for the purpose -of holding the iris diaphragm and Abbé condenser. The raising and -lowering of the sub-stage are accomplished by a rack and pinion. - -5. The =iris diaphragm=, which is held in the sub-stage below the -Abbé condenser, consists of a series of metal plates, so arranged -that the light entering the microscope may be cut off completely or -its amount regulated by moving a control pin. - -6. The =fine adjustment= is located either at the side or at the top -of the limb. It consists of a fine rack and pinion, and is used in -focusing an object when the low-power objective is in position, or in -finding and focusing the object when the high-power objective is in -position. - -7. The =coarse adjustment= is a rack and pinion used in raising and -lowering the body-tube and in finding the approximate focus when -either the high- or low-power objective is in position. - -8. The =body-tube= is the path traveled by the rays of light entering -the objectives and leaving by the eye-piece. To the lower part of the -tube is attached the nose-piece, and resting in its upper part is the -draw-tube, which holds the eye-piece. On the outer surface of the -draw-tube there is a scale which indicates the distance it is drawn -from the body-tube. - -9. The =nose-piece= may be simple, double, or triple, and it is -protected from dust by a circular piece of metal. Double and triple -nose-pieces may be revolved, and like the simple nose-piece they hold -the objectives in position. - - - THE OPTICAL PARTS - -1. The =mirror= is a sub-stage attachment one surface of which is -plain and the other concave. The plain surface is used with an Abbé -condenser when the source of light is distant, while the concave -surface is used with instruments without an Abbé condenser when the -source of light is near at hand. - -[Illustration: FIG. 8.--Compound Microscope - - Eyepiece - Draw Tube - Body Tube - Coarse - Adjustment - Revolving Nosepiece for three Objectives - Fine Adjustment - Stage - Objectives - Limb - Abbi Condenser - Iris Diaphragm - Hinge for Inclining - Substage Attachment - Mirror - Pillar - Foot] - -2. The =Abbé condenser= (Fig. 9) is a combination of two or more -lenses, arranged so as to concentrate the light on the specimen -placed on the stage. The condenser is located in the opening of the -stage, and its uppermost surface is circular and flat. - -[Illustration: FIG. 9--Abbé Condenser] - -3. =Objectives= (Figs. 10, 11, and 12). There are low, medium, and -high-power objectives. The low-power objectives have fewer and -larger lenses, and they magnify least, but they show more of the -object than do the high-power objectives. There are three chief -types of objectives: First, dry objectives; second, wet objectives, -of which there are the water-immersion objectives; and third, the -oil-immersion objectives. The dry objectives are used for most -histological and pharmacognostical work. For studying smaller objects -the water objective is sometimes desirable, but in bacteriological -work the oil-immersion objective is almost exclusively used. The -globule of water or oil, as the case may be, increases the amount of -light entering the objective, because the oil and water bend many -rays into the objective which would otherwise escape. - -[Illustration: FIG. 10.] - -[Illustration: FIG. 11.] - -[Illustration: FIG. 12. Objectives.] - -4. =Eye-pieces= (Figs. 13, 14, and 15) are of variable length, but -structurally they are somewhat similar. The eye-piece consists of a -metal tube with a blackened inner tube. In the centre of this tube -there is a small diaphragm for holding the ocular micrometer. In the -lower end of the tube a lens is fastened by means of a screw. This, -the field lens, is the larger lens of the ocular. The upper, smaller -lens is fastened in the tube by a screw, but there is a projecting -collar which rests, when in position, on the draw-tube. - -[Illustration: FIG. 13.] - -[Illustration: FIG. 14.] - -[Illustration: FIG. 15. Eye-Pieces.] - -The longer the tube the lower the magnification. For instance, a -two-inch ocular magnifies less than an inch and a half, a one-inch -less than a three-fourths of an inch, etc. - -The greater the curvature of the lenses of the ocular the higher will -be the magnification and the shorter the tube-length. - - - FORMS OF COMPOUND MICROSCOPES - -The following descriptions refer to three different models of -compound microscopes: one which is used chiefly as a pharmacognostic -microscope, one as a research microscope stand, while the third type -represents a research microscope stand of highest order, which is -used at the same time for taking microphotographs. - -[Illustration: FIG. 16.--Pharmacognostic Microscope] - - - PHARMACOGNOSTIC MICROSCOPE - -The =pharmacognostic microscope= (Fig. 16) is an instrument -which embodies only those parts which are most essential for the -examination of powdered drugs, bacteria, and urinary sediments. This -microscope is provided with a stage of the dimensions 105 × 105 mm. -This factor and the distance of 80 mm. from the optical centre to the -handle arm render it available for the examination of even very large -objects and preparations, or preparations suspended in glass dishes. -The stand is furnished with a side micrometer, a fine adjustment -having knobs on both sides, thereby permitting the manipulation of -the micrometer screw either by left or right hand. The illuminating -apparatus consists of the Abbé condenser of numerical aperture -of 1.20, to which is attached an iris diaphragm for the proper -adjustment of the light. A worm screw, mounted in connection with the -condenser, serves for the raising and lowering of the condenser, so -that the cone of illuminating pencils can be arranged in accordance -to the objective employed and to the preparation under observation. -The objectives necessary are those of the achromatic type, possessing -a focal length of 16.2 mm. and 3 mm. Oculars which render the best -results in regard to magnification in connection with the two -objectives mentioned are the Huyghenian eye-pieces II and IV so that -magnifications are obtained varying from 62 to 625. It is advisable, -however, to have the microscope equipped with a triple revolving -nose-piece for the objectives, so that provision is made for the -addition of an oil-immersion objective at any time later should the -microscope become available for bacteriological investigations. - - - THE RESEARCH MICROSCOPE - -The =research microscope= used in research work (Fig. 17) must be -equipped more elaborately than the microscope especially designed for -the use of the pharmacognosist. While the simple form of microscope -is supplied with the small type of Abbé condenser, the research -microscope is furnished with a large illuminating apparatus of -which the iris diaphragm is mounted on a rack and pinion, allowing -displacement obliquely to the optical centre, also to increase -resolving power in the objectives when observing those objects which -cannot be revealed to the best advantage with central illumination. -Another iris is furnished above the condenser; this iris becomes -available the instant an object is to be observed without the aid -of the condenser, in which case the upper iris diaphragm allows -proper adjustment of the light. The mirror, one side plane, the -other concave, is mounted on a movable bar, along which it can be -slid--another convenience for the adjustment of the light. The -microscope stage of this stand is of the round, rotating and centring -pattern, which permits a limited motion to the object slide: The -rotation of the microscope stage furnishes another convenience in the -examination of objects in polarized light, allowing the preparation -to be rotated in order to distinguish the polarization properties of -the objects under observation. - -[Illustration: FIG. 17.--Research Microscope] - -[Illustration: FIG. 18.--Special Research Microscope] - - - SPECIAL RESEARCH MICROSCOPE - -A =special research microscope= of the highest order (Fig. 18) -is supplied with an extra large body tube, which renders it of -special advantage for micro-photography. Otherwise in its mechanical -equipment it resembles very closely the medium-sized research -microscope stand, with the exception that the stand is larger in its -design, therefore offering universal application. In regard to the -illuminating apparatus, it is advisable to mention that the one in -the large research microscope stand is furnished with a three-lens -condenser of a numerical aperture of 1.40, while the medium-sized -research stand is provided with a two-lens condenser of a numerical -aperture of 1.20. The stage of the microscope is provided with a -cross motion--the backward and forward motion of the preparation is -secured by rack and pinion, while the side motion is controlled by a -micrometric worm screw. In cases where large preparations are to be -photographed, the draw-tube with ocular and the slider in which the -draw-tubes glide are removed to allow the full aperture of wide-angle -objectives to be made use of. - -[Illustration: FIG. 19.--Greenough Binocular Microscope] - - - BINOCULAR MICROSCOPE - -The =Greenough binocular microscope=, as shown in Fig. 19, consists -of a microscope stage with two tubes mounted side by side and moving -on the same rack and pinion for the focusing adjustment. Either tube -can be used without the other. The oculars are capable of more or -less separation to suit the eyes of different observers. In each -of the drub-like mountings, near the point where the oculars are -introduced, porro-prisms have been placed, which erect the image. -This microscope gives most perfect stereoscopic images, which are -erect instead of inverted, as in the monocular compound microscopes. -The Greenough binocular microscope is especially adapted for -dissection and for studying objects of considerable thickness. - - - POLARIZATION MICROSCOPE - -The =polarization microscope= (Fig. 20) is used chiefly for the -examination of crystals and mineral sections as well as for the -observation of organic bodies in polarized light. It can, however, -also be used for the examination of regular biological preparations. - -[Illustration: FIG. 20.--Polarization Microscope] - -If compared with the regular biological microscope, the polarization -microscope is found characteristic of the following points: it is -supplied with a polarization arrangement. The latter consists of a -polarizer and analyzer. The polarizer is situated in a rotating mount -beneath the condensing system. The microscope, of which the diagram -is shown, possesses a triple “Ahrens” prism of calcite. The entering -light is divided into two polarized parts, situated perpendicularly -to each other. The so-called “ordinary” rays are reflected to one -side by total reflection, which takes place on the inner cemented -surface of the triple prism, allowing the so-called “extraordinary” -rays to pass through the condenser. If the prism is adjusted to -its focal point, it is so situated that the vibration plane of the -extra-ordinary rays are in the same position as shown in the diagram -of the illustration. - -The analyzer is mounted within the microscope-tube above the -objective. Situated on a sliding plate, it can be shifted into -the optical axis whenever necessary. The analyzer consists of a -polarization prism after Glan-Thompson. The polarization plane of the -active extraordinary rays is situated perpendicularly to the plane as -shown in the diagram. The polarization prisms are ordinarily crossed. -In this position the field of the microscope is darkened as long as -no substance of a double refractive index has been introduced between -the analyzer and polarizer. In rotating the polarizer up to the mark -90, the polarization prisms are mounted parallel and the field of -the microscope is lighted again. Immediately above the analyzer and -attached to the mounting of the analyzer a lens of a comparatively -long focal length has been placed in order to overcome the difference -in focus created by the introduction of the analyzer into the optical -rays. - -The condensing system is mounted on a slider, and, furthermore, -can be raised and lowered along the optical centre by means of a -rack-and-pinion adjustment. If lowered sufficiently, the condensing -system can be thrown to the side to be removed from the optical -rays. The condenser consists of three lenses. The two upper lenses -are separately mounted to an arm, which permits them to be tilted to -one side in order to be removed from the optical rays. The complete -condenser is used only in connection with high-power objectives. -As far as low-power objectives are concerned, the lower condensing -lens alone is made use of, and the latter is found mounted to the -polarizer sleeve. Below the polarizer and above the lower condensing -lens an iris diaphragm is found. - -The microscope table is graduated on its periphery, and, furthermore, -carries a vernier for more exact reading. - -The polarization microscope is not furnished with an objective -nose-piece. Every objective, however, is supplied with an individual -centring head, which permits the objective to be attached to -an objective clutch-changer, situated at the lower end of the -microscope-tube. The centring head permits the objectives to be -perfectly centred and to remain centred even if another objective is -introduced into the objective clutch-changer. - -At an angle of 45 degrees to the polarization plane of polarizer and -analyzer, a slot has been provided, which serves for the introduction -of compensators. - -Between analyzer and ocular, another slot is found which permits -the Amici-Bertrand lens to be introduced into the optical axis. The -slider for the Bertrand lens is supplied with two centring screws -whereby this lens can be perfectly and easily centred. The Bertrand -lens serves the purpose of observing the back focal plane of the -microscope objective. In order to allow the Bertrand lens to be -focused, the tube can be raised and lowered for this purpose. An iris -diaphragm is mounted above the Bertrand lens. - -If the Bertrand lens is shifted out of the optical axis, one can -observe the preparation placed upon the microscope stage and, -depending on its thickness or its double refraction, the interference -color of the specimen. This interference figure is called the -orthoscopic image and, accordingly, one speaks of the microscope as -being used as an “orthoscope.” - -After the Bertrand lens has been introduced into the optical axis, -the interference figure is visible in the back focal plane of the -objective. Each point of this interference figure corresponds to -a certain direction of the rays of the preparation itself. This -arrangement permits observation of the change of the reflection of -light taking place in the preparation, this in accordance with the -change of the direction of the rays. This interference figure is -called the conoscopic image, and, accordingly, the microscope is used -as a “conoscope.” - -Many types of polarization microscopes have been constructed; those -of a more elaborate form are used for research investigations; others -of smaller design for routine investigations. - - - - - CHAPTER III - - MICROSCOPIC MEASUREMENTS - - -In making critical examinations of powdered drugs, it is frequently -necessary to measure the elements under observation, particularly in -the case of starches and crystals. - -[Illustration: FIG. 21.--Ocular Micrometer] - - - OCULAR MICROMETER - -Microscopic measurements are made by the =ocular micrometer= (Fig. -21). This consists of a circular piece of transparent glass on the -centre of which is etched a one- or two-millimeter scale divided into -one hundred or two hundred divisions respectively. The value of each -line is determined by standardizing with a stage micrometer. - - - STAGE MICROMETER - -[Illustration: FIG. 22.--Stage Micrometer] - -The =stage micrometer= (Fig. 22) consists of a glass slide upon which -is etched a millimeter scale divided into one hundred equal parts or -lines: each line has a value of one hundredth of a millimeter. - - - STANDARDIZATION OF OCULAR MICROMETER WITH LOW-POWER OBJECTIVE - -Having placed the ocular micrometer in the eye-piece and the stage -micrometer on the centre of the stage, focus until the lines of the -stage micrometer are clearly seen. Then adjust the scales until the -lines of the stage micrometer are parallel with and directly under -the lines of the ocular micrometer. - -Ascertain the number of lines of the stage micrometer covered by the -one hundred lines of the ocular micrometer. Then calculate the value -of each line of the ocular. This is done in the following manner: - -If the one hundred lines of the ocular cover seventy-five lines -of the stage micrometer, then the one hundred lines of the ocular -micrometer are equivalent to seventy-five one-hundredths, or -three-fourths, of a millimeter. One line of the ocular micrometer -will therefore be equivalent to one-hundredth of seventy-five -one-hundredths, or .0075 part of a millimeter, and as a micron is the -unit for measuring microscopic objects, this being equivalent to one -one-thousandth of a millimeter, the value of each line of the ocular -will therefore be 7.5 microns. - -[Illustration: FIG. 23.--Micrometer Eye-Piece] - -With the high-power objective in place, ascertain the value of each -line of the ocular. If one hundred lines of the ocular cover only -twelve lines of the stage micrometer, then the one hundred lines of -the ocular are equivalent to twelve one-hundredths of a millimeter, -the value of one line being equivalent to one one-hundredth of twelve -one-hundredths, or twelve ten-thousandths of a millimeter, or .0012, -or 1.2_µ_. - -It will therefore be seen that objects as small as a thousandth of a -millimeter can be accurately measured by the ocular micrometer. - -In making microscopic measurements it is only necessary to find how -many lines of the ocular scale are covered by the object. The number -of lines multiplied by the equivalent of each line will be the size -of the object in microns, or _micromillimeters_. - -[Illustration: FIG. 24.--Micrometer Eye-Piece] - - - MICROMETER EYE-PIECES - -=Micrometer eye-pieces= (Figs. 23 and 24) may be used in making -measurements. These eye-pieces with micrometer combinations are -preferred by some workers, but the ocular micrometer will meet the -needs of the average worker. - - - MECHANICAL STAGES - -Moving objects by hand is tiresome and unsatisfactory, first, because -of the possibility of losing sight of the object under observation, -and secondly, because the field cannot be covered so systematically -as when a mechanical stage is used for moving slides. - -The =mechanical stage= (Fig. 25) is fastened to the stage by a screw. -The slide is held by two clamps. There is a rack and pinion for -moving the slide to left or right, and another rack and pinion for -moving the slide forward and backward. - -[Illustration: FIG. 25. Mechanical Stage] - - - CAMERA LUCIDA - -The =camera lucida= is an optical mechanical device for aiding the -worker in making drawings of microscopic objects. The instrument is -particularly necessary in research work where it is desirable to -reproduce an object in all its details. In fact, all reproductions -illustrating original work should be made by means of the camera -lucida or by microphotography. - -[Illustration: FIG. 26.--Camera Lucida] - -[Illustration: FIG. 27.--Camera Lucida] - -A great many different types of camera lucidas or drawing apparatus -are obtainable, varying from simple-inexpensive to complex-expensive -forms. Figs. 26, 27, and 28 show simple and complex forms. - -[Illustration: FIG. 28.--Drawing Apparatus] - - - MICROPHOTOGRAPHIC APPARATUS - -The =microphotographic apparatus= (Fig. 29), as the name implies, is -an apparatus constructed in such a manner that it may be attached to -a microscope when we desire to photograph microscopic objects. It -consists of a metal base and a polished metal pillar for holding the -bellows, slide holder, ground-glass observation plate, and eye-piece. -In making photographs, the small end of the bellows is attached to -the ocular of the microscope, the focus adjusted, and the object or -objects photographed. More uniform results are obtained in making -such photographs if an artificial light of an unvarying candle-power -is used. - -[Illustration: FIG. 29.--Microphotographic Apparatus] - -There are obtainable more elaborate microphotographic apparatus than -the one figured and described, but for most workers this one will -prove highly satisfactory. It is possible, by inclining the tube of -the microscope, to make good microphotographs with an ordinary plate -camera. This is accomplished by removing the lens of the camera and -attaching the bellows to the ocular, focusing, and photographing. - - - - - CHAPTER IV - - HOW TO USE THE MICROSCOPE - - -In beginning work with the compound microscope, place the base of the -microscope opposite your right shoulder, if you are right-handed; or -opposite your left shoulder, if you are left-handed. Incline the body -so that the ocular is on a level with your eye, if necessary; but -if not, work with the body of the microscope in an erect position. -In viewing the specimen, keep both eyes open. Use one eye for -observation and the other for sketching. In this way it will not be -necessary to remove the observation eye from the ocular unless it be -to complete the details of a sketch. - -=Learn to use both eyes.= Most workers, however, accustom themselves -to using one eye; when they are sketching, they use both eyes, -although it is not necessary to do so. - -=Open the iris diaphragm=, and incline the mirror so that white light -is reflected on the Abbé condenser. Place the slide on the centre -of the stage, and if the slide contains a section of a plant, move -the slide so as to place this specimen over the centre of the Abbé -condenser. Then lower the body by means of the coarse adjustment -until the low-power object, which should always be in position when -work is begun, is within one-fourth of an inch of the stage. Then -raise the body by means of the coarse adjustment until the object, -or objects, in case a powder is being examined, is seen. Open and -close the iris diaphragm, finally adjusting the opening so that the -best possible illumination is obtained for bringing out clearly -the structure of the object or objects viewed. Then regulate the -focus by moving the body up or down by turning the fine adjustment. -When studying cross-sections or large particles of powders, it is -sometimes desirable to make low-power sketches of the specimen. In -most cases, however, only sufficient time should be spent in studying -the specimen to give an idea of the size, structure, and general -arrangement or plan or structure if a section of a plant, or, if -a powder, to note its striking characters. All the finer details -of structure are best brought out with the high-power objective in -position. - -In =placing the high-power objective in position=, it is first -necessary to raise the body by the coarse adjustment; then open the -iris diaphragm, and lower the body until the objective is within -about one-eighth of an inch of the slide. Now raise the tube by -the fine adjustment until the object is in focus, then gradually -close the iris diaphragm until a clear definition of the object is -obtained. Now proceed to make an accurate sketch of the object or -objects being studied. - -In =using the water or oil-immersion objectives= it is first -necessary to place a drop of distilled water or oil, as the case may -be, immediately over the specimen, then lower the body by the coarse -adjustment until the lens of the objective touches the water or the -oil. Raise the tube, regulate the light by the iris diaphragm, and -proceed as if the high-power objectives were in position. - -The water or oil should be removed from the objectives and from the -slide when not in use. - -After the higher-powered objective has been used, the body should -be raised, and the low-power objective placed in position. If the -draw-tube has been drawn out during the examination of the object, -replace it, but be sure to hold one hand on the nose-piece so as to -prevent scratching the objective and Abbé condenser by their coming -in forceful contact. Lastly, clean the mirror with a soft piece of -linen. In returning the microscope to its case, or to the shelf, -grasp the limb, or the pillar, firmly and carry as nearly vertical as -possible in order not to dislodge the eye-piece. - - - ILLUMINATION - -The illumination for microscopic work may be from natural or -artificial sources. - -[Illustration: FIG. 30.--Micro Lamp] - -It has been generally supposed that the best possible illumination -for microscopic work is diffused sunlight obtained from a northern -direction. No matter from what direction diffused sunlight is -obtained, it will be found suitable for microscopic work. In no case -should direct sunlight be used, because it will be found blinding -in its effects upon the eyes. Natural illumination--diffused -sunlight--varies so greatly during the different months of the -year, and even during different periods of the day, that individual -workers are resorting more and more to artificial illumination. The -particular advantage of such illumination is due to the fact that -its quality and intensity are uniform at all times. There are many -ways of securing such artificial illumination, no one of which has -any particular advantage over the other. Some workers use an ordinary -gas or electric light with a color screen placed in the sub-stage -below the iris diaphragm. In other cases a globe filled with a weak -solution of copper sulphate is placed in such a way between the -source of light and the microscope that the light is focused on the -mirror. Modern mechanical ingenuity has devised, however, a number of -more convenient micro lamps (Fig. 30). These lamps are a combination -of light and screen. In some forms a number of different screens come -with each lamp, so that it is possible to obtain white-, blue-, or -dark-ground illumination. The type of the screen used will be varied -according to the nature of the object studied. - - - CARE OF THE MICROSCOPE - -If possible, the microscope should be stored in a room of the same -temperature as that in which it is to be used. In any case, avoid -storing in a room that is cooler than the place of use, because when -it is brought into a warmer room, moisture will condense on the -ocular objectives and mirrors. - -Before beginning work remove all moisture, dust, etc., from the inner -and outer lenses of the ocular, the objectives, the Abbé condenser, -and the mirror by means of a piece of soft, old linen. When the work -is finished the optical parts should be thoroughly cleaned. - -If reagents have been used, be sure that none has got on the -objectives or the Abbé condenser. If any reagent has got on these -parts, wash it off with water, and then dry them thoroughly with soft -linen. - -The inner lenses of the eye-pieces and the under lens of the Abbé -condenser should occasionally be cleaned. The mechanical parts of the -stand should be cleaned if dust accumulates, and the movable surfaces -should be oiled occasionally. Never attempt to make new combinations -of the ocular or objective lenses, or transfer the objectives or -ocular from one microscope to another, because the lenses of any -given microscope form a perfect lens system, and this would not be -the case if they were transferred. Keep clean cloths in a dust-proof -box. Under no circumstances touch any of the optical parts with your -fingers. - - - PREPARATION OF SPECIMENS FOR CUTTING - -Most drug plants are supplied to pharmacists in a dried condition. -It is necessary, therefore, to boil the drug in water, the time -varying from a few minutes, in the case of thin leaves and herbs, up -to a half hour if the drug is a thick root or woody stem. If a green -(undried) drug is under examination, this first step is not necessary. - -If the specimen to be cut is a leaf, a flower-petal, or other thin, -flexible part of a plant, it may be placed between pieces of elder -pith or slices of carrot or potato before cutting. - - - SHORT PARAFFIN PROCESS - -In most cases, however, more perfect sections will be obtained if the -specimens are embedded in paraffin, by the quick paraffin process, -which is easily carried out. - -After boiling the specimen in water, remove the excess of moisture -from the outer surface with filter paper or wait until the water has -evaporated. Next make a mould of stiff cardboard and pour melted -paraffin (melting at 50 or 60 degrees) into the mould to a height of -about one-half inch, when the paraffin has solidified. This may be -hastened by floating it on cool or iced water instead of allowing it -to cool at room temperature. - -The specimens to be cut are now placed on the paraffin, with glue, if -necessary, to hold them in position, and melted paraffin poured over -the specimens until they are covered to a depth of about one-fourth -of an inch. Cool on iced water, trim off the outer paraffin to the -desired depth, and the Specimen will be in a condition suitable for -cutting. - -Good workable sections may be cut from specimens embedded by this -quick paraffin method. After a little practice the entire process -can be carried out in less than an hour. This method of preparing -specimens for cutting will meet every need of the pharmacognosist. - - - LONG PARAFFIN PROCESS - -In order to bring out the structure of the =protoplast= (living part -of the cell), it will be necessary to begin with the living part of -the plant and to use the long paraffin method or the collodion method. - -Small fragments of a leaf, stem, or root-tip are placed in -chromic-acid solution, acetic alcohol, picric acid, chromacetic -acid, alcohol, etc., depending upon the nature of the specimen under -observation. The object of placing the living specimen in such -solutions is to kill the protoplast suddenly so that the parts of the -cell will bear the same relationship to each other that they did in -the living plant, and to fix the parts so killed. - -After the fixing process is complete, the specimen is freed of the -fixing agent by washing in water. From the water-bath the specimens -are transferred successively to 10, 20, 40, 60, 70, 80, 90, and -finally 100 per cent alcohol. In this 100 per cent alcohol-bath the -last traces of moisture are removed. The length of time required to -leave the specimens in the different percentages of alcohols varies -from a few minutes to twenty-four hours, depending upon the size and -the nature of the specimen. - -[Illustration: FIG. 31.--Paraffin-embedding Oven] - -After dehydration the specimen is placed in a clearing -agent--chloroform or xylol--both of which are suitable when embedding -in paraffin. The clearing agents replace the alcohol in the cells, -and at the same time render the tissues transparent. From the -clearing agent the specimen is placed in a weak solution of paraffin, -dissolved xylol, or chloroform. The strength of the paraffin solution -is gradually increased until it consists of pure paraffin. The -temperature of the paraffin-embedding oven (Fig. 31) should not be -much higher than the melting-point of the paraffin. - -The specimen is now ready to be embedded. First make a mould of -cardboard or a lead-embedding frame (Fig. 32), melt the paraffin, and -then place the specimen in a manner that will facilitate cutting. -Remove the excess of paraffin and cut when desired. - -[Illustration: FIG. 32.--Paraffin Blocks] - -In using the collodion method for embedding fibrous specimens, -as wood, bark, roots, etc., the specimen is first fixed with -picric acid, washed with water, cleared in ether-alcohol, embedded -successively in two, five, and twelve per cent ether-alcohol -collodion solution, and finally embedded in a pure collodion bath. - - - CUTTING SECTIONS - -Specimens prepared as described above may be cut with a hand -microtome or a machine microtome. - - - HAND MICROTOME - -In cutting sections by a =hand microtome=, it is necessary to place -the specimen, embedded in paraffin or held between pieces of elder -pith, carrot, or potato, over the second joints of the fingers, -then press the first joints firmly upon the specimen with the thumb -pressed against it. If they are correctly held, the specimens will be -just above the level of the finger and the end of the thumb, and the -joint will be below the level of the finger. - -[Illustration: FIG. 33.--Hand Microtome] - -Hold the section cutter (Fig. 33) firmly in the hand with the flat -surface next to the specimen. While cutting the section, press your -arm firmly against your chest, and bend the wrist nearly at right -angles to the arm. Push the cutting edge of the microtome toward the -body and through the specimen in such a way as to secure as thin a -section as possible. Do not expect to obtain nice, thin sections -during the first or second trials, but continued practice will enable -one to become quite efficient in cutting sections in this manner. - -When the examination of drugs is a daily occurrence, the above method -will be found highly satisfactory. - - - MACHINE MICROTOMES - -When a number of sections are to be prepared from a given specimen, -it is desirable to cut the sections on a machine microtome, -particularly when the sections are to be prepared for the use of -students, in which case they should be as uniform as possible. - -Great care should be exercised in cutting sections with a machine -microtome--first, in the selection of the type of the microtome; and -secondly, in the style of knife used in cutting. - -For soft tissues embedded in paraffin or collodion, the =rotary -microtome= with vertical knife will give best results. The thickness -of the specimen is regulated by mechanical means, so that in cutting -the sections it is only necessary to turn a crank and remove the -specimens from the knife-edge, unless there is a ribbon-carrier -attachment. If the sections are being cut from a specimen embedded -by the quick paraffin method, it is best to drop the section in a -metal cup partly filled with warm water. This will cause the paraffin -to straighten out, and the specimen will uncoil. After sufficient -specimens have been cut, the cup should be placed in a boiling-water -bath until the paraffin surrounding the sections melts and floats on -the water. Before removing the specimen from the water-bath, it is -advisable to shake the glass vigorously in order to cause as many -specimens as possible to settle to the bottom of the cup. The cup -is then placed in iced water or set aside until the paraffin has -solidified. The cake-like mass is then removed from the cup, and the -sections adhering to its under surface are removed by lifting them -carefully off with the flat side of the knife and transferring them, -together with the sections at the bottom of the cup, to a wide-mouth -bottle, and covered with alcohol, glycerine, and water mixture; or if -it is desired to stain the specimens, they should be placed in a weak -alcoholic solution. - -Specimens having a hard, woody texture should be cut on a =sliding -microtome= by means of a special wood knife, which is especially -tempered to cut woody substances. Woody roots, wood, or thick bark -may be cut readily on this microtome when they have been embedded by -the quick paraffin process. The knife in the sliding microtome is -placed in a horizontal position, slanting so that the knife-edge is -drawn gradually across the specimen. After cutting, the sections are -treated as described above. - -The thickness of the sections is regulated by mechanical means. -After a section has been cut, the block containing the specimen is -raised by turning a thumb-screw. In this microtome the knife, as in -the rotary type, is fixed, and the block containing the specimen is -movable. - -If the specimen has been infiltrated with, and embedded in, paraffin -or collodion, the treatment of the sections after cutting should be -different. - -In the case of paraffin, the sections are fastened directly to the -slide, and the paraffin is dissolved by either chloroform or xylol. -The specimen is then placed in 100, 95, and 45 per cent alcohol, -and then washed in water. These sections are now stained with -water-stains, brought back through alcohol, cleared, and mounted in -Canada balsam. - -If alcoholic stains are used, it will not be necessary to dehydrate -before staining, and the dehydration after staining will also be -eliminated. - -Sections infiltrated with collodion are either stained directly -without removing the collodion or after removal. - - - FORMS OF MICROTOMES - -The =hand cylinder microtome= (Fig. 34) consists of a cylindrical -body. The clamp for holding the specimen is near the top below the -cutting surface. At the lower end is attached a micrometer screw with -a divided milled head. When moved forward one division, the specimen -is raised 0.01 mm. This micrometer screw has an upward movement of -10 mm. The cutting surface consists of a cylindrical glass ring. - -[Illustration: FIG. 34.--Hand Cylinder Microtome] - -[Illustration: FIG. 35.--Hand Table Microtome] - -The =hand table microtome= (Fig. 35) is provided with a clamp, by -which it may be attached to the edge of a table or desk. The cutting -surface consists of two separated but parallel glass benches. The -object is held by a clamp and is raised by a micrometer screw, which, -when moved through one division by turning the divided head, raises -the specimen 0.01 mm. - -The =sliding microtome= has a track of 250 mm. The object is held -by a clamp and its height regulated by hand. The disk regulating -the micrometer screw is divided into one hundred parts. When this -is turned through one division, the object is raised 0.005 mm. or -5 microns, at the same time a clock-spring in contact with teeth -registers by a clicking sound. If the disk is turned through two -divisions, there will be two clicks, etc. In this way is regulated -the thickness of the sections cut. When the micrometer screw has been -turned through the one hundred divisions, it must be unscrewed, the -specimen raised, and the steps of the process repeated. The knife is -movable and is drawn across the specimen in making sections. - -[Illustration: FIG. 36.--Base Sledge Microtome] - -The =base sledge microtome= (Fig. 36) has a heavy iron base which -supports a sliding-way on which the object-carrier moves. The -object-carrier is mounted on a solid mass of metal, and is provided -with a clamp for holding the object. The object is raised by turning -a knob which, when turned once, raises the specimen one to twenty -microns, according to how the feeding mechanism is set. - -Sections thicker than twenty microns may be obtained by turning the -knob two or more times. The knife is fixed and is supported by two -pillars, the base of which may be moved forward or backward in such a -manner that the knife can be arranged with an oblique or right-angled -cutting surface. - -[Illustration: FIG. 37.--Minot Rotary Microtome] - -The =Minot rotary microtome= (Fig. 37) has a fixed knife, held in -position by two pillars, and a movable object-carrier. The object is -firmly secured by a clamp, and it is raised by a micrometer screw. -The screw is attached to a wheel having five hundred teeth on its -periphery. A pawl is adjusted to the teeth in such a way that, when -moved by turning a wheel to which it is attached, specimens varying -from one to twenty-five microns in thickness may be cut, according -to the way the adjusting disk is set. When the mechanism has been -regulated and the object adjusted for cutting, it is only necessary -to turn a crank in cutting sections. - - - CARE OF MICROTOMES - -When not in use, microtomes should be protected from dust, and all -parts liable to friction should be oiled. - -Microtome knives should be honed as often as is necessary to insure -a proper cutting edge. After cutting objects, the knives should be -removed, cleaned, and oiled. - -It should be kept clearly in mind that special knives are required -for cutting collodion, paraffin, and frozen and woody sections. The -cutting edges of the different knives vary considerably, as is shown -in the preceding cuts. - - - - - CHAPTER V - - REAGENTS - - -Little attention is given in the present work to micro-chemical -reactions for the reason that their value has been much overrated in -the past. A few reagents will be found useful, however, and these few -are given, as well as their special use. They are as follows: - - - LIST OF REAGENTS - -=Distilled Water= is used in the alcohol, glycerine, and water -mixture as a general mounting medium. It is used when warm as a test -for inulin and it is used in preparing various reagents. - -=Glycerine= is used in preparing the alcohol, glycerine, and water -mixture, in testing for aleurone grains, and as a temporary mounting -medium. - -=Alcohol= is used in preparing the alcohol, glycerine, and water -mixture, in testing for volatile oils. - -=Acetic Acid=. Both dilute and strong solutions are used in testing -for aleurone grains, cystoliths, and crystals of calcium oxalate. - -=Hydrochloric Acid= is used in connection with phloroglucin as a test -for lignin and as a test for calcium oxalate. - -=Ferric Chloride Solution= is used as a test for tannin. - -=Sulphuric Acid= is used as a test for calcium oxalate. - -=Tincture Alkana= is used when freshly prepared by macerating the -granulated root with alcohol and filtering, as a test for resin. - -=Sodium Hydroxide=. A five per cent solution is used as a test for -suberin and as a clearing agent. - -=Copper Ammonia= is used as a test for cellulose. - -=Ammonical Solution of Potash= is used as a test for fixed oils. -The solution is a mixture of equal parts of a saturated solution of -potassium hydroxide and stronger ammonia. - -=Oil of Cloves= is used as a clearing fluid for sections preparatory -to mounting in Canada balsam. - -=Canada Balsam= is used as a permanent mounting medium for dehydrated -specimens, and as a cement for ringing slides. - -=Paraffin= is used for general embedding and infiltrating. - -=Lugol’s Solution= is used as a test for starch and for aleurone -grains and proteid matters. - -=Osmic Acid=. A two per cent solution is used as a test for fixed -oils. - -=Alcohol, Glycerine, and Water Mixture= is used as a temporary -mounting medium and as a qualitative test for fixed oils. - -=Chlorzinc Iodide= is used as a test for suberin, lignin, cellulose, -and starch. - -=Analine Chloride= is used as a test for lignified cell walls of bast -fibres and of stone cells. - -=Phloroglucin=. A one per cent alcoholic solution is used in -connection with hydrochloric acid as a test for lignin. - -=Hæmatoxylin-Delifields= is used as a test for cellulose. - -[Illustration: FIG. 38.--Reagent Set] - - - REAGENT SET - -Each worker should be provided with a set of =reagent bottles= -(Fig. 38). Such a set may be selected according to the taste of the -individual, but experience has shown that a 30 c.c. bottle with a -ground-in pipette and a rubber bulb is preferable to other types. In -such forms the pipettes are readily cleaned, and the rubber bulbs can -be replaced when they become old and brittle. The entire set should -be protected from dust by keeping it in a case, the cover of which -should be closed when the set is not in use. - - - MEASURING CYLINDER - -In order accurately to measure micro-chemical reagents, it is -necessary to have a standard 50 c.c. cylinder (Fig. 39) graduated to -c.c.’s. Such a cylinder should form a part of the reagent set. - -[Illustration: FIG. 39.--Measuring Cylinder] - - - STAINING DISHES - -[Illustration: FIG. 40.--Staining Dish] - -There is a great variety of =staining dishes= (Fig. 40), but for -general histological work a glass staining dish with groves for -holding six or more slides and a glass cover is most desirable. - - - - - CHAPTER VI - - HOW TO MOUNT SPECIMENS - - -The method of procedure in mounting specimens for study varies -according to the nature of the specimen, its preliminary treatment, -and the character of the mount to be made. As to duration, mounts are -either temporary or permanent. - - - TEMPORARY MOUNTS - -In preparing a =temporary mount=, place the specimen in the centre -of a clean slide and add two or more drops of the temporary mounting -medium, which may be water, or a mixture of equal parts of alcohol, -glycerine, and water, or some micro-chemical reagent, as weak Lugol’s -solution, solution of chloral hydrate, etc. Cover this with a cover -glass and press down gently. Remove the excess of the mounting -medium with a piece of blotting paper. Now place the slide on the -stage and proceed to examine it. Such mounts can of course be used -only for short periods of study; and when the period of observation -is finished, the specimen should be removed and the slide washed, -or the slide washing may be deferred until a number of such slides -have accumulated. At any rate, when the mounting medium dries, the -specimen is no longer suitable for observation. - - - PERMANENT MOUNTS - -Permanent mounts are prepared in much the same way as temporary, but -of course the mounting medium is different. The kind of permanent -mounting medium used depends upon the previous treatment of the -specimen. If the specimen has been preserved in alcohol or glycerine -and water, it is usually mounted in glycerine jelly. If the specimen -in question is a powder, it is placed in the centre of the slide and -a drop or two of glycerine, alcohol, and water mixture added, unless -the powder was already in suspension in such a mixture. Cut a small -cube of glycerine jelly and place it in the centre of the powder -mixture. Lift up the slide by means of pliers, or grasp the two -edges between the thumb and finger and hold over a small flame of an -alcohol lamp, or place on a steam-bath until the glycerine jelly has -melted. Next sterilize a dissecting needle, cool, and mix the powder -with the glycerine jelly, being careful not to lift the point of the -needle from the slide during the operation. If the mixing has been -carefully done, few or no air-bubbles will be present; but if they -are present, heat the needle, and while it is white hot touch the -bubbles with its point, and they will disappear. Now take a pair of -forceps and, after securing a clean cover glass near the edge, pass -them three times through the flame of the alcohol lamp. While holding -it in a slanting position, touch one side of the powder mixture and -slowly lower the cover glass until it comes in complete contact with -the mixture. Now press gently with the end of the needle-handle, and -set it aside to cool. When it is cool, place a neatly trimmed label -on one end of the slide, on which write the name of the specimen, -the number of the series of which it is to form a part, etc. Any -excess of glycerine jelly, which may have been pressed out from the -edges of the cover glass, should not be removed at once, but should -be allowed to remain on the slide for at least one month in order to -allow for shrinkage due to evaporation. At the end of a month remove -the glycerine jelly by first passing the blade of a knife, held in -a vertical position, the back of the knife being next to the slide, -around the edge of the cover glass. After turning the knife-blade so -that the flat side is in contact with slide, remove the jelly outside -of the cover glass. Any remaining fragments should be removed with -a piece of old linen or cotton cloth. Finally, ring the edge of the -cover glass with microscopical cement, of which there are many types -to be had. If the cleaning has been done thoroughly, there is no -better ringing cement than Canada balsam. - -In mounting cross-sections, the method of procedure is similar to the -above, with the exception that the glycerine jelly is placed at the -side of the specimen and not in the centre. While melting the jelly, -incline the slide in order to allow the melted glycerine jelly to -flow gradually over the specimen, thus replacing the air contained in -the cells and intercellular spaces. Finish the mounting as directed -above, but under no conditions should you stir the glycerine jelly -with the section. - -If specimens, after having been embedded in paraffin or collodion, -are cut, cleared, stained, and dehydrated, they are usually mounted -in Canada balsam. A small drop of this substance, which may be -obtained in collapsible tubes, is placed at one side of the specimen. -While inclining the slide, gently heat until the Canada balsam covers -the specimen. Secure a cover glass by the aid of pliers, pass it -through the flame three times, and lower it slowly while holding it -in an inclined position. Press gently on the cover glass with the -needle-handle, and keep in a horizontal position for twenty-four -hours, then place directly in a slide box or cabinet, since no -sealing is required. - -Glycerine is sometimes used to make permanent mounts, but it is -unsatisfactory, because the cover glass is easily removed and the -specimen spoiled or lost, unless ringed--a procedure which is not -easily accomplished. If the specimen is to be mounted in glycerine, -it must first be placed in a mixture of alcohol, glycerine, and -water, and then transferred to glycerine. Lactic acid is another -permanent liquid-mounting medium, which is unsatisfactory in the same -way as glycerine, but like glycerine, there are certain special cases -where it is desirable to use it. When this is used, the slides should -be kept in a horizontal position, unless ringed. - - - COVER GLASSES - -Great care should be used In the selection of =cover glasses=, -however, not only as regards their shape but as to their thickness. -The standard tube length of the different manufacturers makes an -allowance of a definite thickness for cover glasses. It is necessary, -therefore, to use cover glasses made by the manufacturer of the -microscope in use. - -Cover glasses are either square or round. Of each there are four -different thicknesses and two different sizes. The standard -thicknesses are: The small size is designated three-fourths and the -large size seven-eighths. - -[Illustration: FIG. 41.--Round Cover Glass] - -[Illustration: FIG. 42.--Square Cover Glass] - -[Illustration: FIG. 43.--Rectangular Cover Glass] - -=Cover glasses= are circular (Fig. 41), square (Fig. 42), or -rectangular (Fig. 43) pieces of transparent glass used in -covering the specimens mounted on glass slides. A few years ago -much difficulty was experienced in obtaining uniformly thick and -transparent cover glasses, but no such difficulty is experienced -to-day. The type of cover glass used depends largely upon the -character of the specimen to be mounted. The square and rectangular -glasses are selected when a series of specimens are to be mounted, -but in mounting powdered drugs and histological specimens the round -cover glasses are preferable because they are more sightly and more -readily cleaned and rinsed. - - - GLASS SLIDES - -[Illustration: FIG. 44.--Glass Slide] - -=Glass slides= (Fig. 44) are rectangular pieces of transparent glass -used as a mounting surface for microscopic objects. The slides are -usually three inches long by one inch wide, and they should be -composed of white glass, and they should have ground and beveled -edges. Slides should be of uniform thickness, and they should not -become cloudy upon standing. - - - SLIDE AND COVER-GLASS FORCEPS - -Slides and cover glasses should be grasped by their edges. To the -beginner this is not easy. In order to facilitate holding slides and -cover glasses during the mounting process, one may use a slide and a -cover-glass =forceps=. The slide forceps consists of wire bent and -twisted in such a way that it holds a slide firmly when attached to -its two edges. - -[Illustration: FIG. 45.--Histological Forceps] - -[Illustration: FIG. 46.--Forceps] - -[Illustration: FIG. 47.--Sliding-pin Forceps] - -There are various forms of cover-glass holders, but only two types as -far as the method of securing the cover glass is concerned. First, -there are the bacteriological and the histological forceps (Fig. 45), -which are self-closing. The two blades of such forceps must be forced -apart by pressure in securing the cover glass. The second type of -forceps is that in which the two blades are normally separated (Fig. -46), it being necessary to press the blades to either side of the -cover glass in order to secure and hold it. There is a modification -of this type of forceps which enables one to lock the blades by means -of a sliding pin (Fig. 47), after the cover glass has been secured. -It is well to accustom oneself to one type, for by so doing one may -become dexterous in its use. - - - NEEDLES - -[Illustration: FIG. 48.--Dissecting Needle] - -Two =dissecting needles= (Fig. 48) should form a part of the -histologist’s mounting set. The handles may be of any material, but -the needle should be of tempered steel and about two inches long. - - - SCISSORS - -[Illustration: FIG. 49.--Scissors] - -Almost any sort of =scissors= (Fig. 49) will do for histology work, -but a small scissors with fine pointed blades, are preferred. -Scissors are useful in trimming labels and in cutting strips of -leaves and sections of fibrous roots that are to be embedded and cut. - - - SCALPELS - -[Illustration: FIG. 50.--Scalpels] - -=Scalpels= (Fig. 50) have steel blades and ebony handles. These vary -in regard to size and quality of material. The cheaper grades are -quite as satisfactory, however, as the more expensive ones, and for -general use a medium-sized blade and handle will be found most useful. - - - TURNTABLE - -[Illustration: FIG. 51.--Turntable] - -Much time and energy may be saved by ringing slides on a =turntable= -(Fig. 51). There is a flat surface upon which to rest the hand -holding the brush with cement, and a revolving table upon which the -slide to be ringed is held by means of two clips. In ringing slides, -it is only necessary to revolve the table, and at the same time to -transfer the cement to the edge of the cover glass from the brush -held in the hand. - - - LABELING - -There are many ways of =labeling slides=, but the best method is to -place on the label the name of the specimen, the powder number, and -the box, the tray or cabinet number. For example: - - Powdered Arnica Flowers - No. 80--Box A--600. - - - PRESERVATION OF MOUNTED SPECIMENS - -[Illustration: FIG. 52.--Slide Box] - -[Illustration: FIG. 53.--Slide Tray] - -Accurately mounted, labeled, and ringed slides should be filed away -for future study and reference. Such =filing= may be done in slide -boxes, in slide trays, or in cabinets. Slide boxes are to be had -of a holding capacity varying from one to one hundred slides. For -general use, slide boxes (Fig. 52) holding one hundred slides will -be found most useful. Some workers prefer trays (Fig. 53), because -of the saving of time in selecting specimens. Trays hold twenty -slides arranged in two rows. The cover of the tray is divided into -two sections so that, if desired, only one row of slides is uncovered -at a time. Slide cabinets (Fig. 54) are particularly desirable for -storing large individual collections, particularly when the slides -are used frequently for reference. Large selections of slides should -be numbered and card indexed in order to facilitate finding. - -[Illustration: FIG. 54.--Slide Cabinet] - - - - - Part II - - TISSUES CELLS, AND CELL CONTENTS - - - - - CHAPTER I - - THE CELL - - -The =cell= is the unit of structure of all plants. In fact the cell -is the plant in many of the lower forms--so called unicellular -plants. All plants, then, consist of one or more cells. - -While cells vary greatly in size, form, color, contents, and -function, still in certain respects their structure is identical. - - - TYPICAL CELL - -The typical vegetable cell is composed of a living portion or -=protoplast= and an external covering, or =wall=. The protoplast -includes everything within the wall. It is made up of a number of -parts, each part performing certain functions yet harmonizing with -the work of the cell as a whole. The protoplast (protoplasm) is a -viscid substance resembling the white of an egg. The protoplast, when -unstained and unmagnified, appears structureless, but when stained -with dyes and magnified, it is found to be highly organized. The -two most striking parts of the protoplast are the =cytoplasm= and -the =nucleus=. The part of the protoplast lining the innermost part -of the wall is the =ectoplast=, which is less granular and slightly -denser than most of the =cytoplasm=. The cytoplasm is decidedly -granular in structure. - -In the cytoplasm occurs one or more cavities, =vacuoles=, filled with -=cell sap=. Embedded in the cytoplasm are numerous =chromatophores=, -which vary in color in the different cells, from colorless to yellow, -to red, and to green. The =nucleus= is the seat of the vital activity -of the cell, and the seat of heredity. The whole life and activity of -the cell centre, therefore, in and about the nucleus. - -The outer portion of the nucleus consists of a thin -membrane or wall. The membrane encloses numerous granular -particles--=chromatin=--which are highly susceptible to organic -stains. Among the granules are thread-like particles or =linin=. Near -the centre of the nucleus are one or more small rounded nucleoli. The -liquid portion of the nucleus, filling the membranes and surrounding -the chromatin, linin, and nucleoli, is the =nuclear sap=. - -Other cell contents characteristic of certain cells are crystals, -starch, aleurone, oil, and alkaloids. The detailed discussion of -these substances will be deferred until a later chapter. - -The =cell wall= which surrounds the protoplast is a product of its -activity. The structure and composition of the wall of any given cell -vary according to the ultimate function of the cell. The walls may be -thin or thick, porous or non-porous, and colored or colorless. The -composition of cell walls varies greatly. The majority of cell walls -are composed of cellulose, in other cells of linin, in others of -cutin, and in still others of suberin, etc. In the majority of cells -the walls are laid down in a series of layers one over the other by -apposition, similar to the manner of building a pile of paper from -separate sheets. The first layer is deposited over the primary wall, -formed during cell division; to this is added another layer, etc. A -modification of this manner of growth is that in which the layers are -built up one over the other, but the building is gradually done by -the deposit of minute particles of cell-wall substance over the older -deposits. Such walls are never striated, as is likely to be the case -in cell walls formed by the first method. In other cells the walls -are increased in thickness by the deposition of new wall material in -the older membrane. The cell walls will be discussed more fully when -the different tissues are studied in detail. - - - INDIRECT CELL DIVISION (KARYOKINESIS) - -The purpose of cell division is to increase the number of cells -of a tissue, an organ, an organism, or to increase the number of -organisms, etc. Such cell divisions involve, first, an equal division -of the protoplast and, secondly, the formation of a wall between -the divided protoplasts. The first changes in structure of a cell -undergoing division occur in the nucleus. - - - CHANGES IN A CELL UNDERGOING DIVISION - -The =linin threads= become thicker and shorter. The =chromatin -granules= increase in size and amount; the threads and chromatin -granules separate into a definite number of segments or =chromosomes= -(Plate 1, Fig. 2). The nuclear membrane becomes invested with a -fibrous protoplasmic layer which later separates and passes into -either end of the cell, there forming the =polar caps= (Plate 1, Fig. -3). - -The =nuclear membrane= and the =nucleoli= disappear at about this -time. Two fibres, one from each polar cap, become attached to -opposite sides of the individual chromosomes. Other fibres from -the two polar caps unite to form the =spindle fibres=, which thus -extend from pole to pole. All these spindle fibres form the =nuclear -spindle= (Plate 1, Fig. 5). - -The chromosomes now pass toward the division centre of the cell or -=equatorial plane= and form, collectively, the =equatorial plate= -(Plate 1, Fig. 5). At this point of cell division, the chromosomes -are =U=-shaped, and the curved part of the chromosomes faces the -equatorial plane. The chromosomes finally split into two equal -parts (Plate 1, Fig. 6). The actual separation of the halves of -chromosomes is brought about by the attached polar fibres, which -contract toward the polar caps (Plate 1, Fig. 7). The chromosomes are -finally drawn to the polar caps (Plate 1, Fig. 8). The chromosomes -now form a rounded mass. They then separate into linin threads -and chromatin granules. Nucleoli reappear, and nuclear sap forms. -Finally, a nuclear membrane develops. The spindle fibres, which still -extend from pole to pole, become thickened at the equatorial plane -(Plate 1, Fig. 8), and finally their edges become united to form the -=cell-plate= (Plate 1, Fig. 9), which extends across the cell, thus -completely separating the mother cell into two daughter cells. After -the formation of the cell-plate, the spindle fibres disappear. The -cell becomes modified to form the =middle lamella=, on either side of -which the daughter protoplast adds a cellulose layer. The ultimate -composition of the middle lamella and the composition and structure -of the cell wall will differ according to the function which the cell -will finally perform. - -[Illustration: PLATE 1 - - Nine figures, showing stages in the cell-division common to the - onion root (_Allium cepa_, L.)] - - - ORIGIN OF MULTICELLULAR PLANTS - -All multicellular plants are built up by the repeated cell division -of one original cell. If the cells formed are similar in structure -and function, they form a tissue. In multicellular plants many -different kinds of tissues will be formed as a result of cell -division, since there are many different functions to be performed by -such an organism. When several of these tissues become associated and -their functions are correlated, they form an organ. The association -of several organs in one form makes an organism. The oak-tree is an -organism. It is made up of organs known as flowers, leaves, stems, -roots, etc. Each of these organs is in turn made up of several kinds -of tissue. In some cases it is difficult to designate a single -function to an aggregation of cells (tissue). In fact, a tissue may -perform different functions at different periods of its existence -or it may perform two functions at one and the same time; as an -example, stone cells, whose primary function is mechanical, in many -cases function as storage tissue. The cells forming the tissues of -the plant, in fact, show great adaptability in regard to the function -which they perform. Nevertheless there is a predominating function -which all tissues perform, and the structure of the cells forming -such tissues is so uniform that it is possible to classify them. - -The functional classification of tissues is chosen for the purpose -of demonstrating the adaptation of cell structure to cell function. -If the cells performing a similar function in the different plants -were identical in number, distribution, form, color, size, structure, -and cell contents, there would not be a science of histology upon -which the art of microscopic pharmacognosy is based. It may be said, -however, with certainty, that the cells forming certain of the -tissues of any given species of plant will differ in a recognizable -degree from cells performing a similar function in other species of -plants. Often a tissue is present in one plant but absent in another. -For example, many aquatic plants are devoid of mechanical fibrous -cells. The barks of certain plants have characteristic stone cells, -while in many other barks no stone cells occur. Many leaves have -characteristic trichomes; others are free from trichomes, etc. Yet -all cells performing a given function will structurally resemble -each other. In the present work the nucleus and other parts of the -living protoplast will not be considered, for the reason that these -parts are not in a condition suitable for study, because most drugs -come to market in a dried condition, a condition which eliminates -the possibility of studying the protoplast. The general structure of -the cells forming the different tissues will first be considered, -then their variation, as seen in different plants, and finally their -functions. - - - - - CHAPTER II - - THE EPIDERMIS AND PERIDERM - - -The epidermis and its modifications, the hypodermis and the periderm, -form the dermal or protective outer layer or layers of the plant. - -The epidermis of most leaves, stems of herbs, seeds, fruits, floral -organs, and young woody stems consists of a single layer of cells -which form an impervious outer covering, with the exception of the -stoma. - - - LEAF EPIDERMIS - -The cells of the =epidermis= vary in size, in thickness of the side -and end walls, in form, in arrangement, in character of outgrowths, -in the nature of the surface deposits, in the character of -wall--whether smooth or rough--and in size. - -In cross-sections of the leaf the character of both the side and end -walls is easily studied. - -In surface sections--the view most frequently seen in powders--the -side walls are more conspicuous than the end wall (Plates 2 and 3). -This is so because the light is considerably retarded in passing -through the entire length of the side walls, while the light is -retarded only slightly in passing through the end wall. The light in -this case passes through the width (thickness) of the wall only. The -outer walls of epidermal cells are characteristic only when they are -striated, rough, pitted, colored, etc. In the majority of leaves the -outer wall of the epidermal cells is not diagnostic in powders, or in -surface sections. - -The thickness of the end and side walls of epidermal cells differs -greatly in different plants. - -As a rule, leaves of aquatic and shade-loving plants, as well as the -leaves of most herbs have thinner walled epidermal cells than have -the leaves of plants growing in soil under normal conditions, or than -have the leaves of shrubs and trees. - -[Illustration: PLATE 2 - - LEAF EPIDERMIS - - 1. Uva-ursi (_Arctostaphylos uva-ursi_, [L.] Spring). - 2. Boldus (_Peumus boldus_, Molina). - 3. Catnip (_Nepeta cataria_, L.). - 4. Digitalis (_Digitalis purpurea_, L.). - 4-A. Origin of hair.] - -[Illustration: PLATE 3 - - LEAF EPIDERMIS - - 1. Upper striated epidermis of chirata leaf (_Swertia chirata_, - [Roxb.] Ham.). - 2. Green hellebore leaf (_Veratrum viride_, Ait.). - 3. Boldus leaf (_Peumus boldus_, Molina). - 4. Under epidermis of India senna (_Cassia angustifolia_, Vahl.).] - -The widest possible range of cell-wall thickness is therefore found -in the medicinal leaves, because the medicinal leaves are collected -from aquatic plants, herbs, shrubs, trees, etc. - -The outer wall is always thicker than the side walls. Even the -side walls vary in thickness in some leaves, the wall next to the -epidermis being thicker than the lower or innermost portion of the -wall. Frequently the outermost part of the side walls is unequally -thickened. This is the case in the beaded side walls characteristic -of the epidermis of the leaves of laurus, myrcia, boldus, and -capsicum seed, etc. The thickness of the side walls of the epidermal -cells of most leaves varies in the different leaves. - -In most leaves there are five typical forms of arrangement of -epidermal cells: First, those over the veins which are elongated -in the direction of the length of the leaf; and, secondly, those -on other parts of the leaf which are usually several-sided and not -elongated in any one direction. If the epidermis of the leaf has -stoma, then there is a third type of arrangement of the epidermal -cells around the stoma; fourthly, the cells surrounding the base of -hairs; and fifthly, outgrowths of the epidermis, non-glandular and -glandular hairs, etc. - -It should be borne in mind that in each species of plant the five -types of arrangement are characteristic for the species. - -The character of the outer wall of the epidermal cells differs -greatly in different plants. In most cases the wall is smooth; senna -is an example of such leaves. In certain other leaves the wall -is rough, the roughness being in the form of striations. In some -cases the striations occur in a regular manner; belladonna leaf is -typical of such leaves. In other instances the wall is striated in -an irregular manner as shown in chirata epidermis. Very often an -epidermis is rough, but the roughness is not due to striations. -In these cases the epidermis is unevenly thickened, the thin -places appearing as slight depressions, the thick places as slight -elevations. Boldus has a rough, but not a striated surface. - -=Surface deposits= are not of common occurrence in medicinal plants; -waxy deposits occur on the stem of sumac, on a species of raspberry, -on the fruit of bayberry, etc. Resinous deposits occur on the leaves -and stems of grindelia species, and on yerba santa. - -In certain leaves there are two or three layers of cells beneath the -epidermis that are similar in structure to the epidermal cells. These -are called hypodermal cells, and they function in the same way as the -epidermal cells. - -Hypodermal cells are very likely to occur on the margin of the leaf. -Uva-ursi leaf has a structure typical of leaves with hypodermal -marginal cells. Uva-ursi, like other leaves with hypodermal cells has -a greater number of hypodermal cells at the leaf margin than at any -other part of the leaf surface. - -The cutinized walls of epidermal cells are stained red with saffranin. - - - TESTA EPIDERMIS - -=Testa epidermal cells= form the epidermal layers of such seeds as -lobelia, henbane, capsicum, paprika, larkspur, belladonna, scopola, -etc. - -In surface view the end walls are thick and wavy in outline; -frequently the line of union--middle lamella--of two cells is -indicated by a dark or light line, while in others the wall between -two cells appears as a single wall. The walls are porous or -non-porous, and the color of the wall varies from yellow to brown, to -colorless. These cells always occur in masses, composed partially of -entire and partially of broken fragments. - -In lobelia seed (Plate 4, Fig. 2) the line of union of adjacent cell -walls appears as a dark line. The walls are wavy in outline, of a -yellowish-red color and not porous. - -In henbane seed (Plate 4, Fig. 3) the line of union between the cells -is scarcely visible; the walls are decidedly wavy, more so than in -lobelia, and no pits are visible. - -In capsicum seed (Plate 4, Fig. 1) the cells are very wavy and -decidedly porous, the line of union between the cell walls being -marked with irregular spaces and lines. - -In belladonna seed (Plate 5, Fig. 1) the walls between two adjacent -cells are non-striated and non-porous, and extremely irregular in -outline. - -[Illustration: PLATE 4 - - TESTA EPIDERMAL CELLS - - 1. Capsicum seed (_Capsicum frutescens_, L.). - 2. Lobelia seed (_Lobelia inflata_, L.). - 3. Henbane seed (_Hyoscyamus niger_, L.).] - -[Illustration: PLATE 5 - - TESTA CELLS - - 1. Belladonna seed (_Atropa belladonna_, L.). - 2. Star-aniseed (_Illicium verum_, Hooker). - 3. Stramonium seed (_Datura stramonium_, L.).] - -In star-anise seed (Plate 5, Fig. 2) the walls are irregularly -thickened and wavy in outline. - -In stramonium seed (Plate 5, Fig. 3) the walls are very thick, wavy -in outline, and striated. - - - PLANT HAIRS (TRICHOMES) - -In histological work plant hairs are of great importance, as they -offer a ready means of distinguishing and differentiating between -plants, or parts of plants, when they occur in a broken or finely -powdered condition. There is no other element in powdered drugs which -is of so great a diagnostic value as the plant hair. The same plant -will always have the same type of hair, the only noticeable variation -being in the size. In microscopical drug analysis the presence of -hairs is always noted, and in many cases the purity of the powder -can be ascertained from the hairs. Botanists seem to have given -little attention to the study of plant hairs. This accounts for the -fact that information concerning them is very meagre in botanical -literature, and, as far as the author can learn, no one has attempted -to classify them. In systematic work, plant hairs could be used to -great advantage in separating genera and even species. Hairs are, -of course, a factor now in systematic work. The lack of hairs is -indicated by the term glabrous. Their presence is indicated by such -terms as hispid, villous, etc. In certain cases the term indicates -position of the hair as ciliate when the hair is marginal. When hairs -influence the color of the leaf, such terms as cinerous and canescent -are used. In all the cases cited no mention is made of the real -nature of the hair. - -In systematic work, as in pharmacognosy, we must work with dried -material, and it is only those hairs which retain their form under -such conditions which are of classification value. - -Hairs are the most common outgrowths of the epidermal cells. They -are classified as glandular or non-glandular, according to their -structure and function. The glandular hairs will be considered under -synthetic tissue. - -Each group is again subdivided into a number of secondary groups, -depending upon the number of cells present, their form, their -arrangement, their size, their color, the character of their walls, -whether rough or smooth, whether branched or non-branched, whether -curved, twisted, straight, or twisted and straight, whether pointed, -blunt, or forked. - - - FORMS OF HAIRS - - PAPILLÆ - -=Papillæ= are epidermal cells which are extended outward in the form -of small tubular outgrowths. - -Papillæ occur on the following parts of the plant: flower-petals, -stigmas, styles, leaves, stems, seeds, and fruits. Papillæ occur on -only a few of the medicinal leaves. - -The under surface of both Truxillo (Plate 6, Fig. 3) and Huanuca coca -have very small papillæ. The outermost wall of these papillæ are much -thicker than the side walls. The papillæ of klip buchu (Plate 6, Fig. -4), an adulterant of true buchu, has large thick-walled papillæ. - -The velvety appearance of most flower-petals (Plate 6, Figs. 2 and -5) is due to the presence of papillæ. The papillæ of flower-petals -are very variable. In calendula flowers (Plate 6, Fig. 1) they -are small, yellowish in color, and the outer wall is marked with -parallel striations which appear as small teeth in cross-section. -The ray petal papillæ of anthemis consist of rather large, broad, -blunt papillæ with slightly striated walls. The papillæ of the ray -petals of the white daisy consist of papillæ which have medium sized, -cone-shaped papillæ with finely striated walls. The papillæ of the -flower stigma vary greatly in different flowers. In some cases two or -more types of papillæ occur, but even in these cases the papillæ are -characteristic of the species. - -The papillæ differ greatly in the case of the flowers of the -compositæ, where two types of flowers are normally present--namely, -the ray flowers and the disk flowers. - -In all cases observed the papillæ of the stigma of the ray flowers -are always smaller than the papillæ of the stigma of the disk -flowers. It would appear from extended observation that the papillæ -of the ray flower stigma are being gradually aborted. The papillæ of -the style are always different from the papillæ of the stigma. The -style papillæ are always smaller, and they are of a different form. - -[Illustration: PLATE 6 - - PAPILLÆ - - 1. Calendula flowers (_Calendula officinalis_, L.). - 2. White daisy ray flower (_Chrysanthemum leucanthemum_, L.). - 3. Coca leaf (_Erythroxylon coca_, Lamarck). - 4. Klip buchu. - 5. Anthemis ray petal (_Anthemis nobilis_, L.).] - - - UNICELLULAR NON-GLANDULAR HAIRS - -=True plant hairs= are tubular outgrowths of the epidermal cell, the -length of these outgrowths being several times the width of the hair. - -The unicellular hairs are common to many plants. The two groups -of non-glandular unicellular hairs are, first, the solitary; and -secondly, the clustered hairs. - -=Solitary unicellular hairs= occur on the leaves of chestnut, yerba -santa, lobelia, cannabis indica, the fruit of anise, and the stem of -allspice, senna, and cowage. - -Chestnut hairs (Plate 7, Fig. 1) have smooth yellowish-colored walls, -and the cell cavity contains reddish-brown tannin. These hairs occur -solitary or clustered; the clustered hairs normally occur on the -leaf, but in powdering the drug, individual hairs of the cluster -become separated or solitary. - -Yerba santa hairs (Plate 7, Fig. 4) are twisted, the lumen or cell -cavity is very small, and the walls, which are very thick, are -grayish-white. - -Lobelia hairs (Plate 7, Fig. 5) are very large. The walls are -grayish-white, and the outer surface extends in the form of small -elevations which make the hair very rough. The hair tapers gradually -to a solid point. - -Cannabis indica hairs (Plate 7, Fig. 6) are curved. The apex tapers -to a point and the base is broad, and it frequently contains deposits -of calcium carbonate. The walls are grayish-white in appearance, and -rough. The roughness increases toward the apex. - -The hairs of anise (Plate 7, Fig. 7) are mostly curved; the walls are -thick, yellowish-white, and the outer surface is rough; this is due -to the numerous slight centrifugal projections of the outer wall. - -Allspice stem hairs (Plate 7, Fig. 2) have smooth walls. The cell -cavity is reddish-brown. The hair is curved. - -The hair of senna (Plate 7, Fig. 10) is light greenish-yellow with -rough papillose walls. The hair is usually curved and tapering, and -it does not have any characteristic cell contents. - -[Illustration: PLATE 7 - - UNICELLULAR SOLITARY HAIRS - - 1. Chestnut leaf (_Castanea dentata_, [Marsh] Borkh). - 2. Allspice stems (_Pimento, officinalis_, Lindl.). - 3. Cowage. - 4. Yerba santa (_Eriodictyon californicum_, [H. and A.] Greene). - 5. Lobelia (_Lobelia inflata_, L.). - 6. Cannabis indica (_Cannabis saliva_, L.). - 7. Anise fruit (_Pimpinella anisum_, L.). - 8. Hesperis matronalis (_Hesperis matronalis_, L.). - 9. Galphimia glauca (_Galphimia glauca_, Cav.). - 10. Senna (_Cassia angustifolia_, Vahl.).] - -[Illustration: PLATE 8 - - CLUSTERED UNICELLULAR HAIRS - - 1. and 2. European oak (_Quercus infectoria_, Olivier). - 3. Kamala (_Mallotus philippinensis_, [Lam.] [Muell.] Arg.). - 4. Witch-hazel leaf (_Hamamelis virginiana_, L.). - 5. Althea leaf (_Althæa officinalis_, L.).] - -Cowage hairs (Plate 7, Fig. 3) are lance-shaped, and they -terminate in a sharp point. The outer wall contains numerous -recurved teeth-like projections. The cell cavity is filled with a -reddish-brown contents which are somewhat fissured. - -=Clustered unicellular hairs= occur on the leaves of chestnut, -witch-hazel, althea, European oak, etc. In European oak (Plate 8, -Figs. 1 and 2) clusters of two and three hairs occur. The walls are -yellowish-white, smooth, and the tip of the hair is solid. - -In kamala (Plate 8, Fig. 3) clusters of seven or more hairs occur; -the walls are yellowish, and the cell cavity is reddish-brown. In -witch-hazel leaf (Plate 8, Fig. 4) clusters of a variable number -of hairs occur. The hairs, which are of various lengths, have -yellowish-white, thick, smooth walls, and reddish cell contents. - -In althea leaf (Plate 8, Fig. 5) the hairs are nearly straight and -the walls are smooth. The basal portions of the hair are strongly -pitted. - -=Branched solitary unicellular hairs= occur on the leaves of hesperis -matronalis (Plate 7, Fig. 8), and on galphimia glauca (Plate 7, Fig. -9). - -The hair of hesperis matronalis has smooth walls, and the two -branches grow out nearly parallel to the leaf surface. - -The hair of galphimia glauca has rough walls, and the two branches -grow upward in a bifurcating manner. - - - MULTICELLULAR HAIRS - -=Multicellular= hairs are divided into the uniseriate and the -multiseriate hairs. Both of these groups are divided into the -branched and the non-branched hairs, as follows: - - 1. =Uniseriate=. - (_A_) =Non-branched.= - (_B_) =Branched.= - - 2. =Multiseriate.= - (_A_) =Non-branched.= - (_B_) =Branched.= - -=Multicellular uniseriate non-branched hairs= occur on the leaves of -digitalis, Western and Eastern skullcap, peppermint, thyme, yarrow, -arnica flowers, and sumac fruit. - -[Illustration: PLATE 9 - - MULTICELLULAR UNISERIATE NON-BRANCHED HAIRS - - 1. Digitalis leaf (_Digitalis purpurea_, L.). - 2. Arnica flower (_Arnica montana_, L.). - 3. Western skullcap plant (_Scutellaria canescens_, Nutt.). - 4. Eastern skullcap plant (_Scutellaria lateriflora_, L.). - 5. Peppermint leaf (_Mentha piperita_, L.). - 6. Thyme leaf (_Thymus vulgaris_, L.). - 7. Yarrow flowers (_Achillea millefolium_, L.). - 8. Wormwood leaf (_Artemisia absinthium_, L.). - 9. Sumac fruit (_Rhus glabra_, L.).] - -Digitalis hairs (Plate 9, Fig. 1) are made up of a varying number of -uniseriate-arranged cells of unequal length, frequently placed at -right angles to the cells above and below; the walls are of a whitish -color, and are rough or smooth. - -Eastern skullcap (Plate 9, Fig. 4) has hairs with not more than four -cells; these hairs are curved, and the walls are whitish, sometimes -smooth, but usually rough. In Western skullcap (Plate 9, Fig. 3) the -hairs have sometimes as many as seven cells. The walls are white and -rough, and the individual cells of the hair are much larger than are -the cells of the hairs of true skullcap. - -Peppermint (Plate 9, Fig. 5) has from one to eight cells. The hair is -curved, and the walls are very rough. - -Thyme (Plate 9, Fig. 6) has short, thick, rough-walled trichomes, the -terminal cell usually being bent at nearly right angles to the other -cells. - -Yarrow hairs (Plate 9, Fig. 7) have a variable number of cells. In -all the hairs the basal cells are short and broad, while the terminal -cell is greatly elongated. - -Arnica hairs (one form, Plate 9, Fig. 2) have frequently as many as -four cells, the terminal cell being longer than the basal cells. The -walls are white and smooth. - -Sumac-fruit hairs (Plate 9, Fig. 9) have spindle-shaped, -reddish-colored hairs. - -=Multicellular multiseriate non-branched hairs= occur on cumin fruit -and on the tubular part of the corolla of calendula. - -The hairs on cumin fruit vary considerably in size. All the hairs -are spreading at the base and blunt or rounded at the apex. The -cells forming the hair are narrow and the walls are thick. Three -differently sized hairs are shown in Plate 10, Fig. 1. - -The hairs of the base of the ligulate petals of calendula (Plate 10, -Fig. 2) are biseriate. The hairs are very long and the walls are very -thin. - -=Multicellular uniseriate branched hairs= occur on the leaves of -dittany of Crete, mullen, and on the calyx of lavender flowers. - -The dittany of Crete (Plate 11, Fig. 3) hair is smooth-walled, and -the branches are alternate. - -In mullen (Plate 11, Fig. 1) the hairs have whorled branches, the -walls are smooth, and the cell cavity usually contains air. - -[Illustration: PLATE 10 - - MULTICELLULAR MULTISERIATE NON-BRANCHED HAIRS - - 1. Cumin (_Cuminum cyminum_, L.). - 2. Marigold (_Calendula officinalis_, L.).] - -[Illustration: PLATE 11 - - MULTICELLULAR UNISERIATE BRANCHED HAIRS - - 1. Mullen leaf (_Verbascum thapsus_, L.). - 2. Lavender flowers (_Lavandula vera_, D. C.). - 3. Dittany of Crete (_Origanum dictamnus_, L.).] - -The lavender hairs (Plate 11, Fig. 2) have mostly opposite branches, -and the walls are rough. Thus the multicellular branched hairs may be -divided into subgroups which have alternate, opposite, whorled, or in -certain hairs irregularly arranged branches. Each class may be again -subdivided according to color, character of cell termination, etc., -as cited at the beginning of the chapter. - -Occasionally multicellular hairs assume the form of a shield (Plate -12, Fig. 1); in such cases the hair is termed peltate, as in the -non-glandular multicellular hair of shepherdia canadensis. - -Hairs grow out from the surface of the epidermis in a perpendicular, -a parallel, or in an oblique direction. Hairs which grow parallel or -oblique to the surface are usually curved, and the outer curved part -of the wall is usually thicker than the inner curved wall. - -The mature hairs of some plants consist of dead cells. In other -plants the cells forming the hair are living. When dried, those -hairs, which were dead before drying, contain air; while those hairs -which were living before drying, show great variation in color and in -the nature of the cell contents. The contents are either organic or -inorganic. The commonest organic constituent is dried protoplasm. In -cannabis indica are deposits of calcium carbonate. - -=Multicellular multiseriate branched hairs= are the ultimate division -of the pappus of erigeron, aromatic goldenrod, arnica, grindelia, -boneset, and life-everlasting. - -The hairs of erigeron (Plate 13, Figs. 1 and 2) are slender; the -walls are porous. Each hair terminates in two cells, which are -greatly extended and sharp-pointed; the branches from the basal part -of the hairs (Plate 13, Fig. 1) are of about the same length as the -apical branches. - -The hairs of aromatic goldenrod (Plate 13, Figs. 3 and 4) are larger -than those of erigeron; the diameter is greater and the walls are -non-porous. The apex of the hair terminates in a group of about four -cells of unequal length, which are sharp-pointed. The branches of the -basal cells (Plate 13, Fig. 3) are similar to the branches of the -apical cells. - -The hairs of arnica (Plate 14, Figs. 1 and 2) have thick, strongly -porous walls; the branches terminate in sharp points. The apex of the -hair terminates in a single cell. The basal branches (Plate 14, Fig. -2) are much longer than special branches. - -[Illustration: PLATE 12 - - NON-GLANDULAR MULTICELLULAR HAIRS - _Shepherdia canadensis_, [L.] Nutt.] - -[Illustration: PLATE 13 - - MULTICELLULAR MULTISERIATE BRANCHED HAIRS - - 1. Basal hairs of erigeron (_Erigeron canadensis_, L.). - 2. Apical hairs of erigeron (_Erigeron canadensis_, L.). - 3. Basal hairs of aromatic goldenrod (_Solidago odora_, Ait.). - 4. Apical hairs of aromatic goldenrod (_Solidago odora_, Ait.).] - -The hair of grindelia (Plate 14, Figs. 3 and 4) has very thick walls -with numerous elongated pores. The apex of the hair terminates in -a cluster of cells with short, free, sharp-pointed ends. The basal -branches (Plate 14, Fig. 4) are longer than the apical branches. - -Boneset hair (Plate 15, Figs. 1 and 2) has non-porous walls. The -apex of the hair terminates in two blunt-pointed cells. The terminal -wall is thicker than the side wall. Some of the branches lower -down terminate in cells with very thick or solid points. The basal -branches (Plate 15, Fig. 1) are longer, but the cells are narrower -and more strongly tapering than are the branches of the apical part -of the hair. - -Life-everlasting (Plate 15, Figs. 3 and 4) has uniformly thickened -but non-porous walls. The hair terminates in two blunt-pointed, -greatly elongated cells. - -The basal branches (Plate 15, Fig. 4) are narrower, slightly -tapering, and the base of the branches frequently curve downward. - -The cell cavities of these hairs are filled with air. - -The walls of hairs are composed of cutin, of lignin, and of cellulose. - - - PERIDERM - -The =periderm= is the outer protective covering of the stems -and roots of mature shrubs and trees. The periderm replaces the -epidermis. The periderm may be composed of cork cells, stone -cell-cork, or a mixture of cork, parenchyma, fibres, stone cells, etc. - - - CORK PERIDERM - -The typical periderm is made up of =cork cells=. Cork cells vary in -appearance, according to the part of the cell viewed. - -[Illustration: PLATE 14 - - MULTICELLULAR MULTISERIATE BRANCHED HAIRS - - 1. Apical hairs arnica (_Arnica montana_, L.). - 2. Basal hairs arnica (_Arnica montana_, L.). - 3. Apical hairs grindelia (_Grindelia squarrosa_, [Pursh] Dunal). - 4. Basal hairs grindelia (_Grindelia squarrosa_, [Pursh] Dunal).] - -[Illustration: PLATE 15 - - MULTICELLULAR MULTISERIATE BRANCHED HAIRS - - 1. Apical hairs boneset (_Eupatorium perfoliatum_, L.). - 2. Basal hairs boneset (_Eupatorium perfoliatum_, L.). - 3. Apical hairs life-everlasting (_Gnaphalium obtusifolium_, L.). - 4. Basal hairs life-everlasting (_Gnaphalium obtusifolium_, L.).] - -On surface view (Plate 16, Fig. A) the cork cells are angled in -outline and are made up of from four to seven side walls; five- -and six-sided cells are more common than the four-and seven-sided -cells. Surface sections of cork cells show their length and width. -These side walls usually appear nearly white, while the end wall, -particularly of the outermost cork cells, usually appears brown or -reddish-brown, or in some cases nearly black. - -Cork cells on cross-section are rectangular in form, and they are -arranged in superimposed rows, the number of rows being gradually -increased as the plant grows older. Such an increase in the number of -rows of cork cells is shown in the cross-section of cascara sagrada -(Plate 16, Fig. C). - -Cork cells fit together so closely that there is no intercellular -spaces between the cells. In this case two rows of cork cells occupy -no greater space than the solitary row of cork cells immediately over -and external to them. As a rule, the outermost layers of cork cells -have a narrower radial diameter than the cork cells of the underlying -layers. This is due to the fact that these outer cells are stretched -as the stem increases in diameter. This view shows the height of -cork cells, but not always the length, which will, of course, vary -according to the part of the cell cut across. In a section a few -millimeters in diameter, however, all the variations in size may be -observed. The color of the walls is nearly white. - -The cavity may contain tannin or other substances. When tannin is -present, the cavity is of a brownish or brownish-red color, or it may -be nearly black. Most barks appear devoid of any colored or colorless -cell contents. - -The radial section (Plate 16, Fig. B) of cork cells shows the height -of the cells and the width of the cells at the point cut across. Some -cells will be cut across their longest diameter, while others will -be cut across their shortest diameter. Cork cells are, therefore, -smaller in radial section than they are in cross-section. The color -of the walls is white, and the color and nature of the cell contents -vary for the same reasons that they vary in cross-sections. - -The number of layers of cork cells occurring in cross- and -radial-sections varies according to the age of the plant, to the type -of plant, and to the conditions under which the plant is growing. - -The number of layers of cork cells is not of diagnostic importance, -nor is the surface view of cork cells diagnostic except in certain -isolated cases. - -[Illustration: PLATE 16 - - PERIDERM OF CASCARA SAGRADA (_Rhamnus purshiana_, D.C.) - - _A._ 1, Outline of cork cells; 2, Line of contact of adjoining cork - cells. - - _B._ Radial longitudinal section of cascara sagrada. 1, Cork cells; - 2, Phellogen; 3, Forming parenchyma cells; 4, Cortical parenchyma - cells. - - _C._ Cross-section of cascara sagrada. 1, Cork cells; 2, Phellogen; - 3, Forming parenchyma cells; 4, Cortical parenchyma cells.] - -The presence or absence of cork or epidermal tissue in powders must -always be noted. The presence of cork enables one to distinguish -Spanish from Russian licorice. In like manner, the presence of -epidermis enables one to distinguish the pharmacopœial from the -unofficial peeled calamus. The absence of epidermis in Jamaica ginger -is one of the means by which this variety is distinguished from the -other varieties of ginger, etc. - -In canella alba the periderm is replaced by stone cell-cork. That is, -the cells forming the periderm are of a typical cork shape, but the -walls are lignified, unequally thickened, and the inner or thicker -walls are strongly porous, and the walls are of a yellowish color. -Stone cell-cork forms the periderm of clove bark also, but the cells -are narrower and longer, and the inner wall is not so thick or porous -as is the case in canella alba bark. - - - STONE CELL PERIDERM - -In canella alba (Plate 17, Fig. B) cork periderm is frequently -replaced by stone cells, particularly in the older barks. These stone -cells form the periderm because they replace the cork periderm, which -fissures and scales off as the root increases in diameter. - -The side and end walls of cork cells are of nearly uniform diameter. -Exceptions occur, but they are not common. In buchu stem (Plate -101, Fig. 3), the cork cells have thick outer walls, but thin sides -and inner walls. The cell cavity contains reddish-brown deposits of -tannin. - - - PARENCHYMA AND STONE CELL PERIDERM - -As the trees and shrubs increase in diameter, cracks or fissures -occur in the periderm, or corky layer. In such cases the phellogen -cells divide and redivide in such manner as to cut off a portion of -the parenchyma cells, stone cells, and fibres of the cortex which -is inside of and below the fissure. All the parenchyma cells, etc., -exterior to the newly formed cork cells soon lose their living-cell -contents, since their food-supply is cut off by the impervious walls -of the cork cells. In time they are forced outward by the developing -cork cells until they partially or completely fill the break in the -periderm. In white oak bark (Plate 18), as in other barks, a large -part of the periderm is composed of dead and discolored cortical -cells. - -[Illustration: PLATE 17 - - _A._ Cross-section of Mandrake Rhizome (_Podophyllum peltatum_, L.). - 1. Epidermis. - 2. Phellogen. - 3. Cortical parenchyma. - _B._ Stone cell periderm of white cinnamon (_Canella alba_, Murr.).] - -[Illustration: PLATE 18 - - PERIDERM OF WHITE OAK (_Quercus alba_, L.) - - 1. Outer layer of cork cells. 2. Cortical parenchyma cells. 3. - Stone cells. 4. Phellogen. 5. Cortical parenchyma cells.] - - - ORIGIN OF CORK CELLS - -The cork cells are formed by the meristimatic phellogen cells, which -originate from cortical parenchyma. These cells divide into two -cells, the outer changing into a cork cell, while the inner cell -remains meristimatic. In other instances the outer cell remains -meristimatic, while the inner cell changes into a cortical parenchyma -cell. The development of a cortical parenchyma cell from a divided -phellogen cell is shown in Plate 101, Fig. 6. Both the primary and -secondary cork cells originate from the phellogen or cork cambrium -layer. Cork cells do not contain living-cell contents; in fact, in -the majority of medicinal barks the cork cells contain only air. - -The walls of typical cork cells are composed, at least in part, of -suberin, a substance which is impervious to water and gases. In -certain cases layers of cellulose, lignin, and suberin have been -identified. Suberin, however, is present in all cork cells, and in -some cases all of the walls of cork cells are composed of suberin. - -Suberized cork cells are colored yellow with strong sodium hydroxide -solutions and by chlorzinciodide. - - - - - CHAPTER III - - - MECHANICAL TISSUES - - -The =mechanical tissues= of the plant form the framework around -which the plant body is built up. These tissues are constructed and -placed in such a manner in the different organs of the plant as to -meet the mechanical needs of the organ. Many underground stems and -roots which are subjected to radial pressure have the hypodermal -and endodermal cells arranged in the form of a non-compressible -cylinder. Such an arrangement is seen in sarsaparilla root (Plate -38, Fig. 4). The mechanical tissue of the stem is arranged in the -form of solid or hollow columns in order to sustain the enormous -weight of the branches. In roots the mechanical tissue is combined -in ropelike strands, thereby effectively resisting pulling stresses. -The epidermis of leaves subjected to the tearing force of the wind -has epidermal cells with greatly thickened walls, particularly at the -margin of the leaf. The epidermal cells of most seeds have very thick -and lignified cell walls, which effectively resist crushing forces. - -The cells forming mechanical tissues are: bast fibres, wood -fibres, collenchyma cells, stone cells, testa epidermal cells, and -hypodermal and endodermal cells of certain plants. The walls of the -cells forming mechanical tissues are thick and lignified, with the -exception of the collenchyma cells and a few of the fibres. Lignified -cells are as resistive to pulling and other stresses as similar sized -fragments of steel. The hardness of their wall and their resistance -to crushing explain the fact that they usually retain their form in -powdered drugs and foods. - - - BAST FIBRES - -One of the most important characters to be kept in mind in studying -bast fibres is the structure of the wall. In fact, the author’s -classification of bast fibres is based largely on wall structure. -Such a classification is logical and accurate, because it is based -upon permanent characters. Another character used in classifying bast -fibres is the nature of the cell, whether branched or non-branched. -In fact, this latter character is used to separate all bast fibres -into two fundamental groups--namely, branched bast fibres and -non-branched bast fibres. The third important character utilized in -classifying fibres is the presence or absence of crystals. - - Bast fibres are classified as follows: - 1. =Crystal bearing.= - 2. =Non-crystal bearing.= - - The crystal-bearing fibres are divided into two classes: - 1. =Of leaves.= - 2. =Of barks.= - - The non-crystal bearing are divided into: - 1. =Branched.= - 2. =Non-branched.= - - The branched and non-branched are divided into four classes: - 1. =Non-porous and non-striated.= - 2. =Porous and non-striated.= - 3. =Striated and non-porous.= - 4. =Porous and striated.= - - - CRYSTAL-BEARING BAST FIBRES - -The =crystal-bearing fibres= are composed (1) of groups of fibres, -(2) of crystal cells, and (3) of crystals. In these cases the groups -of fibres are large, and they are frequently completely covered by -crystal cells, which may or may not contain a crystal. The crystals -found on the fibres from the different plants vary considerably in -size and form. As a rule, the fibres when separated are free of -crystal cells and crystals. This is so because the crystal cells -are exterior to the fibres, and in separating the fibres during -the milling process the crystal cells are broken down and removed -from the fibres. It is common, therefore, to find isolated fibres -and crystals associated with the crystal-bearing fibres. The fibres -which are crystal-bearing may be striated or porous, etc.; but owing -to the fact that the grouping of the fibres and crystals is so -characteristic, little or no attention is paid to the structure of -the individual fibres. - -[Illustration: PLATE 19 - - CRYSTAL-BEARING FIBRES OF BARKS - - 1. Frangula (_Rhamnus frangula_, L.). - 2. Cascara sagrada (_Rhamnus purshiana_, D.C.). - 3. Spanish licorice (_Glycyrrhiza glabra_, L.). - 4. Witch-hazel bark (_Hamamelis virginiana_, L.).] - - -=Crystal-bearing fibres= occur in the barks of frangula (Plate 19, -Fig. 1); cascara sagrada (Plate 19, Fig. 2); witch-hazel (Plate 19, -Fig. 4); in cocillana (Plate 20, Fig. 1); in white oak (Plate 20, -Fig. 2); in quebracho (Plate 20, Fig. 3); and in Spanish licorice -root (Plate 19, Fig. 3). - -The crystal-bearing fibres of leaves are always associated with -vessels or tracheids and with cells with chlorophyl. The presence -or absence of crystal-bearing fibres in leaves should always be -noted. The crystal-bearing fibres of leaves are composed of fragments -of conducting cells, fibres, crystal cells, and crystals. The -crystal-bearing fibres of leaves occur in larger fragments than the -other parts of the leaf, because the fibres are more resistant to -powdering. Having observed that a leaf has crystal-bearing fibres, -in order to identify the powder it is necessary to locate one of the -other diagnostic elements of the leaf--as the papillæ of coca (Plate -21, Fig. 1), or the hair of senna (Plate 21, Fig. 3), or the vessels -in eucalyptus (Plate 21, Fig. 2). - -=Branched bast fibres= occur in only a few of the medicinal plants, -notable examples being tonga root and sassafras root. Occasionally -one is found in mezereum bark. - -The bast fibre of tonga root (Plate 22, Fig. 2) often has seven -branches, but four- and five-branched forms are more common. The -walls are non-porous, non-striated, and nearly white. - -The bast fibre of sassafras (Plate 22, Fig. 1) has thick, non-porous, -and non-striated walls, and the branching occurs usually at one end -only of the fibre. Most of the bast fibres of sassafras root are -non-branched. - - - POROUS AND STRIATED BAST FIBRES - -=Porous and striated= walled bast fibres occur in blackberry bark of -root, wild-cherry bark, and in cinchona bark. - -The fibres of blackberry root bark (Plate 23, Fig. 1) have distinctly -porous and striated walls; the cavity, which is usually greater than -the diameter of the wall, contains starch. These fibres usually occur -as fragments. - -In wild-cherry bark (Plate 23, Fig. 2) the fibre has short, thick, -unequally thickened walls, which are porous and striated. Most of the -fibres are unbroken. - -[Illustration: PLATE 20 - - CRYSTAL-BEARING FIBRES OF BARKS - - 1. Cocillana (_Guarea rusbyi_, [Britton] Rusby). - 2. White oak (_Quercus alba_, L.) - 3. Quebracho (_Aspidosperma quebracho-blanco_, Schlechtendal).] - -[Illustration: PLATE 21 - - CRYSTAL-BEARING FIBRES OF LEAVES - - 1. Coca leaf (_Erythroxylon coca_, Lam.). - 2. Eucalyptus leaf (_Eucalyptus globulus_, Labill). - 3. Senna leaf (_Cassia angustifolia_, Vahl.).] - -[Illustration: PLATE 22 - - BRANCHED BAST FIBRES - - 1. Sassafras root bark (_Sassafras variifolium_, [Salisb.] Kuntze). - 2. Tonga root.] - -Yellow cinchona bark (Plate 23, Fig. 3) has very thick, prominently -striated porous-walled fibres, with either blunt or pointed ends. The -cavity is narrow, and the pores are simple or branched. - - - POROUS AND NON-STRIATED BAST FIBRES - -=Porous and non-striated= bast fibres occur in marshmallow root and -echinacea root. - -The fibres of marshmallow (Plate 24, Fig. 3) usually occur in -fragments. The walls have simple pores, and the diameter of the -cell cavity is very wide; the pores on the upper or lower wall are -circular or oval in outline (end view). - -The bast fibres of echinacea root (Plate 24, Fig. 4) are seldom -broken; the walls are yellow, the pores are simple and numerous. The -edges and surface of the fibres are frequently covered with a black -intercellular substance. - - - NON-POROUS AND STRIATED BAST FIBRES - -=Non-porous and striated= bast fibres occur in elm bark, stillingia -root, and cundurango bark. The bast fibres of elm bark (Plate 25, -Fig. 1) occur in broken, curved, or twisted fragments. The central -cavity is very small, and the walls are longitudinally striated. - -In powdered stillingia root (Plate 25, Fig. 2) the bast fibres are -broken, and the wall is very thick and longitudinally striated. The -central cavity is small and usually not visible. Bast fibres of -cundurango (Plate 25, Fig. 3) are broken in the powder. The cavity -is very narrow, and the striations are arranged spirally, less -frequently transversely. - - - NON-POROUS AND NON-STRIATED BAST FIBRES - -=Non-porous and non-striated= walled bast fibres occur in mezereum -bark, in Ceylon cinnamon, in sassafras root bark, and in soap bark. - -The simplest non-porous and non-striated walled bast fibres are found -in mezereum bark (Plate 26, Fig. 4). The individual fibre is very -long. It often measures over three millimeters in length, so that in -the powder the fibre is usually broken. The wall is non-lignified, -white, non-porous, and of uniform diameter. - -[Illustration: PLATE 23 - - POROUS AND STRIATED BAST FIBRES - - 1. Blackberry root (_Rubus cuneifolius_, Pursh.). - 2. Wild cherry (_Prunus serotina_, Ehrh.). - 3. Yellow cinchona (_Cinchona species_).] - -[Illustration: PLATE 24 - - POROUS AND NON-STRIATED BAST FIBRES - - 1. Sarsaparilla root (Hypoderm), (_Smilax officinalis_, Kunth). - 2. Unicorn root (Endoderm). - 3. Marshmallow root (_Althæa officinalis_, L.). - 4. Echinacea root (_Echinacea angustifolia_, D. C.).] - -[Illustration: PLATE 25 - - NON-POROUS AND STRIATED BAST FIBRES - - 1. Elm bark (_Ulmus fulva_, Michaux). - 2. Stillingia root (_Stillingia sylvatica_, L.). - 3. Cundurango root bark (_Marsdenia cundurango_, [Triana] Nichols).] - -In Ceylon cinnamon (Plate 26, Fig. 2) the bast fibres measure up to -.900 mm. in length, so that in powdering the bark the fibre is rarely -broken. These bast fibres, unlike the bast fibres of mezereum, have -thick, white walls and a narrow cell cavity. Both ends of the fibre -taper gradually to a long, narrow point. - -In Saigon cinnamon the bast fibres are not as numerous as they are -in Ceylon cinnamon. The individual fibres are thicker than in Ceylon -cinnamon, and the walls are yellowish and rough and the ends bluntly -pointed. These fibres are rarely ever free from adhering fragments of -parenchyma tissue. - -In sassafras root bark (Plate 26, Fig. 3) the fibre has one nearly -straight side--the side in contact with the other bast fibres--and -an outer side with a wavy outline, caused by the fibre’s pressing -against parenchyma cells, the point of highest elevation being the -point of the fibre’s growth into the intercellular space between two -cells. The outer part of the wall tapers gradually at either end to a -sharp point. The walls are white, thick, and non-porous. - -In soap bark (Plate 26, Fig. 1) the bast fibres have thick, white, -wavy walls and a narrow cavity. One end of the cell is frequently -somewhat blunt while the opposite end is slightly tapering. - -The branched stone cells of wild-cherry bark have three or more -branches. The pores are small and usually non-branched, and the -striations are very fine and difficult to see unless the iris -diaphragm is nearly closed. The central cavity is very narrow and -frequently contains brown tannin. - -The branched stone cells of hemlock bark are very large; the walls -are white and distinctly porous bordering on the cell cavity, which -contains bright reddish-brown masses of tannin. - -In cross-section bast fibres occur singly or isolated, as in Saigon -cinnamon (Plate 34, Fig. 1); or in groups, as in menispermum (Plate -27, Figs. 1 and 2); or in the form of continuous bands, as in buchu -stem (Plate 100, Fig. 5). - -Bast fibres are seen in longitudinal view in powdered drugs. The cell -cavity shows throughout the length of the fibre. This cavity differs -greatly in different fibres. In soap bark (Plate 26, Fig. 1) there is -scarcely any cell cavity, while in mezereum bark (Plate 26, Fig. 4) -the cell cavity is very large. - -[Illustration: PLATE 26 - - NON-POROUS AND NON-STRIATED BAST FIBRES - - 1. Soap bark (_Quillaja saponaria_, Molina). - 2. Ceylon cinnamon bark (_Cinnamomum zeylanicum_, Nees). - 3. Sassafras root bark (_Sassafras variifolium_, [Salisb.] Kuntze). - 4. Mezereum bark (_Daphne mezereum_, L.).] - -[Illustration: PLATE 27 - - GROUPS OF BAST FIBRES - - 1. Menispermum rhizome (_Menispermum canadensis_, L.). - 2. Althea root (_Althæa officinalis_, L.) showing two groups of bast - fibres.] - -The pores, which are absent in many drugs, are, when present, -either simple, as in echinacea root (Plate 24, Fig. 4), or they are -branched, as in yellow cinchona (Plate 23, Fig. 3). - -In each of the above fibres the length and width of the fibre -are shown. The fibres also have pores of variable length. Such a -variation is common to most fibres with pores. That part of the wall -immediately over or below the cell cavity shows the end view or -diameter of the pore, as in the fibre of marshmallow root (Plate 24, -Fig. 3). As a rule, however, the pores show indistinctly on the upper -and lower wall. - - - OCCURRENCE IN POWDERED DRUGS - -In powdered drugs bast fibres occur singly or in groups. The -individual fibres may be broken, as in mezereum and elm bark, or they -may be entire, as in Ceylon cinnamon and in sassafras bark (Plate 26, -Figs. 2 and 3). - -The lignified walls of bast fibres are colored red by a solution of -phlorogucin and hydrochloric acid, and the walls are stained yellow -by aniline chloride. - -In fact, few of the fibres found in individual plants occur in a -broken condition. - -Isolated bast fibres are circular in outline. Bast fibres, when -forming part of a bundle, have angled outlines when they are -completely surrounded by other bast fibres; but when they occur on -the outer part of the bundle, and when in contact with parenchyma or -other cortical cells, they are partly angled and partly undulated in -outline. - -In the bast fibres the pores are placed at right angles to the length -of the fibre. The side walls show the length of the pore (Plate 24, -Fig. 3); while the upper or lower wall shows the outline, which is -circular, and the pore, which is very minute. - -Most bast fibres have no cell contents. In some cases, however, -starch occurs, as in the bast fibres of rubus. - -The color of the bast fibres varies, being colorless, as in Ceylon -cinnamon; or yellowish-white, as in echinacea; or bright yellow, as -in bayberry bark. - -Bast fibres retain their living-cell contents until fully developed; -then they die and function largely in a mechanical way. - -The walls of bast fibres are composed of cellulose or of lignin. Most -of the bast fibres occurring in the medicinal plants give a strong -lignin reaction. - - - WOOD FIBRES - -=Wood fibres= always occur in cross-sections associated with vessels -and wood parenchyma, from which they are distinguished by their -thicker walls, smaller diameter, and by the nature of the pores, -which are usually oblique and fewer in number than the pores in the -walls of wood parenchyma, and different in form from the pores of -vessels. - -The wood fibre on cross-section (Plate 105, Fig. 4) shows an -angled outline, except in the case of the fibres bordering the -pith-parenchyma, etc., in which case they are rounded on their outer -surface, but angled at the points in contact with other fibres. The -pore of wood fibres is one of the main characteristics which enable -one to distinguish the wood fibres from bast fibres. - -The pores are slanting or strongly oblique (Plate 28, Fig. 2), -and they show for their entire length on the broadest part of the -wall--_i.e._, the upper or the lower surface--while in the side wall -they are oblique; but they are not so distinct as they are on the -broad part of the wall. - -Frequently the pores appear crossed when the upper and the lower wall -are in focus, because the pores are spirally arranged, and the pore -on the under wall throws a shadow across the pore on the upper wall, -or _vice versa_. - -Wood fibres always occur in a broken condition (Plate 28, Fig. 1) in -powdered drugs. These broken fibres usually occur both singly and in -groups in a given powder. - -The color of wood fibres varies greatly in the different medicinal -woods. Fragments of wood are usually adhering to witch-hazel, black -haw, and other medicinal barks. In each of these cases the wood -fibres are nearly colorless. In barberry bark adhering fragments of -wood and the individual fibres are greenish-yellow. The wood fibres -of santalum album are whitish-brown; of quassia, whitish-yellow; of -logwood and santalum rubrum, red. - -[Illustration: PLATE 28 - - WOOD FIBRES - - 1. White sandalwood (_Santalum album_, L.). - 2. Quassia wood (_Picræna excelsa_, [Swartz] Lindl.). - 3. Logwood with crystals (_Hæmatoxylon campechianum_, L.). - 4. Black haw root (_Viburnum prunifolium_, L.).] - -Some wood fibres function as storage cells. In quassia the wood -fibres frequently contain storage starch. The wood fibres of logwood -and red saunders contain coloring substances, which are partially in -the cell cavity and partially in the cell wall. - -The walls of wood are composed largely of lignin. - - - COLLENCHYMA CELLS - -=Collenchyma cells= form the principal medicinal tissue of stems of -herbs, petioles of leaves, etc. In certain herbs the collenchyma -forms several of the outer layers of the cortex of the stem. In -motherwort, horehound, and in catnip the collenchyma cells occur -chiefly at the angles of the stem. In motherwort (Plate 29, Fig. -B) there are twelve bundles, one large bundle at each of the four -angles, and two small bundles, one on either side of the large -bundle. In catnip (Plate 29, Fig. A) there are four large masses, one -at each angle of the stem. - -Collenchyma cells differ from parenchyma cells in a number of -ways: first, the cell cavity is smaller; secondly, the walls are -thicker, the greater amount of thickening being at the angles of the -cells--that is, the part of the cell wall which is opposite the usual -intercellular space of parenchyma cells, while the wall common to -two adjoining cells usually remains unthickened. In horehound stem -(Plate 30, Fig. 2) the thickening is so great at the angles that no -intercellular space remains. In the side column of motherwort stem -(Plate 30, Fig. 1) the thickening between the cells has taken place -to such an extent that the cell cavities become greatly separated and -arranged in parallel concentric rows. - -The collenchyma of the outer angle of motherwort stem (Plate 30, Fig. -3) is greatly thickened at the angles. There are no intercellular -spaces between the cells, and cell cavity is usually angled in -outline instead of circular, as in the cells of horehound. In certain -plants intercellular spaces occur between the cells, and the walls -are striated instead of being non-striated, as in the stems of -horehound, motherwort, and catnip. - -[Illustration: PLATE 29 - - _A._ Diagrammatic sketch of the cross-section of catnip stem - (_Nepeta cataria_, L.). 1. Collenchyma occurring at the four angles - of the stem. - - _B._ Diagrammatic sketch of the cross-section of motherwort stem - (_Leonurus cardiaca_, L.). 1, 2, 3. Twelve masses of collenchyma - tissue occurring at the four sides of the stem.] - -[Illustration: PLATE 30 - - COLLENCHYMA CELLS - - 1. Cross-section of a side column of the collenchyma of motherwort - stem (_Leonurus cardiaca_, L.). - - 2. Cross-section of the collenchyma of horehound stem (_Marrubium - vulgare_, L.). - - 3. Cross-section of the collenchyma of the outer angle of - motherwort stem.] - -Collenchyma cells retain their living contents at maturity. Many -collenchyma cells, particularly of the outer layers of bark and the -collenchyma of the stems of herbs, contain chlorophyll. - -The walls of collenchyma consist of cellulose. - - - STONE CELLS - -=Stone cells=, like bast fibres, are branched or non-branched. Each -group is then separated into subgroups according to wall structure -(whether striated, or pitted and striated, etc.), thickness of wall -and of cell cavity, color of wall and of cell contents, absence of -color and of cell contents, etc. - - - BRANCHED STONE CELLS - -=Branched stone cells= occur in a number of drugs. In witch-hazel -bark (Plate 31, Fig. 2) the walls are thick, white, and very porous. -In some cells the branches are of equal length; in others they are -unequal. In the tea-leaf (Plate 31, Fig. 1) the walls are yellowish -white and finely porous. When the lower wall is brought in focus, it -shows numerous circular pits. These pits represent the pores viewed -from the end. The branches frequently branch or fork. - -Branched stone cells also occur in coto bark, acer spicatum, -star-anise, witch-hazel leaf, hemlock, and wild-cherry barks. - -Non-branched stone cells are divided into two main groups, as follows: - - 1. Porous and striated stone cells, and, - 2. Porous and non-striated stone cells. - - - POROUS AND STRIATED STONE CELLS - -=Porous and striated= walled stone cells occur in ruellia root, -winter’s bark, bitter root, allspice, and aconite. These stone cells -are shown in Plate 33, Figs. 1, 2, 3, 4, and 5. - -The stone cells of ruellia root (Plate 32, Fig. 1) are greatly -elongated, rectangular in form, with thick, white, strongly porous -walls. The central cavity is narrow and is marked with prominent -pores and striations. - -The stone cells of winter’s bark (Plate 32, Fig. 2) vary from -elongated to nearly isodiametric. The pores are very large, the light -yellowish wall is irregularly thickened, and the central cavity is -very large. The pores are prominent. - -[Illustration: PLATE 31 - - BRANCHED STONE CELLS - - 1. Tea leaf (_Thea sinensis_, L.). - 2. Witch-hazel bark (_Hamamelis virginiana_, L.). - 3. Hemlock bark (_Tsuga canadensis_, [L.] Carr). - 4. Wild-cherry bark (_Prunus serotina_, Ehrh.).] - -The stone cell of bitter root (Plate 32, Fig. 3) is nearly -isodiametric. The walls are yellowish white and strongly porous and -striated. The central cavity is about equal to the thickness of the -walls. - -The stone cell of allspice (Plate 32, Fig. 4) is mostly rounded in -form, and when the outer wall only is in focus it shows numerous -round and elongated pores. The central cavity is filled with masses -of reddish-brown tannin. The striations are very prominent. - -The diagnostic stone cell of aconite (Plate 32, Fig. 5) is -rectangular or square in outline; the walls are yellowish and the -central cavity has a diameter many times the thickness of the -wall. The side and surface view of the pores is prominent, and the -striations are very fine. - - - POROUS AND NON-STRIATED STONE CELLS - -=Porous and non-striated stone cells= occur in Ceylon cinnamon, in -calumba root, in dogwood bark, in cubeb, and in echinacea root. - -The diagnostic stone cells of Ceylon cinnamon (Plate 33, Fig. 1) are -nearly square in outline; the walls are strongly porous and the large -central cavity frequently contains starch. - -The stone cells of calumba root (Plate 33, Fig. 2) vary in shape from -rectangular to nearly square, and the walls are greenish yellow, -unequally thickened, and strongly porous. The typical stone cells -contain several prisms, usually four. - -The stone cells of dogwood bark (Plate 33, Fig. 3) have thick, white -walls with simple and branched pores. The central cavity frequently -branches and appears black when recently mounted, owing to the -presence of air. - -The stone cells of cubeb (Plate 33, Fig. 4) are very small, mostly -rounded in outline, with a great number of very fine simple pores -which extend from the outer wall to the central cavity. The wall is -yellow and very thick. - -The stone cells of echinacea root (Plate 33, Fig. 5) are very -irregular in form; the walls are yellowish and porous, and the -central cavity is very large. A black intercellular substance is -usually adhering to portions of the outer wall. - -The color of the walls of the different stone cells is very -variable. In Ceylon cinnamon and ruellia the walls are colorless; -in zanthoxylium, light yellow; in rumex, deep yellow; in cascara -sagrada, greenish yellow. - -The pores of stone cells, like the pores of bast fibres, are either -simple or branched, and they may or may not extend through the entire -wall. Many of the shorter pores extend for only a short distance from -the cell cavity. - -The width of the cell cavity varies considerably in the stone cells -of the different plants. In aconite (Plate 32, Fig. 5), in calumba -(Plate 33, Fig. 2), and in Ceylon cinnamon (Plate 33, Fig. 1), the -cell cavity is several times greater than the thickness of the cell -wall. - -In allspice (Plate 32, Fig. 4), in bitter root (Plate 32, Fig. 3), -the diameter of the cell cavity and the thickness of the wall are -about equal. In cubeb (Plate 33, Fig. 4), in ruellia (Plate 32, Fig. -1), the wall is thicker than the diameter of the cell cavity. - -The cavity of many stone cells contains no characteristic -cell contents. In other stone cells the cell contents are as -characteristic as the stone cell. The stone cells of both Saigon and -Ceylon cinnamon (Plate 33, Fig. 1) contain starch; the stone cells -of calumba (Plate 33, Fig. 2) contain prisms of calcium oxalate; the -stone cells of allspice and sweet-birch bark contain tannin. - -In cross-sections, stone cells occur singly, as in Saigon cinnamon -(Plate 34, Fig. 1), ruellia (Plate 34, Fig. 2); in groups, as in -cascara sagrada (Plate 34, Fig. 3); and in continuous bands, as in -Saigon cinnamon (Plate 34, Fig. 4). - -In powdered drugs, stone cells, like bast fibres, occur singly, as -in ruellia, calumba, etc.; or in groups, as in cascara sagrada, -witch-hazel bark, etc. In most powders they occur both singly and in -groups. - -The individual stone cells are mostly entire, as in ruellia, calumba, -allspice, echinacea, etc. In cascara sagrada many of the stone cells -are broken when the closely cemented groups are torn apart in the -milling process. Many of the branched stone cells of witch-hazel bark -and leaf, wild cherry, etc., also occur broken in the powder. - -[Illustration: PLATE 32 - - POROUS AND STRIATED STONE CELLS - - 1. Ruellia root (_Ruellia ciliosa_, Pursh.). - 2. Winter’s-bark (_Drimys winteri_, Forst.). - 3. Bitterroot (_Apocynum androsæmifolium_, L.). - 4. Allspice (_Pimenta officinalis_, Lindl.). - 5. Aconite (_Aconitum napellus_, L.).] - -[Illustration: PLATE 33 - - POROUS AND NON-STRIATED STONE CELLS - - 1. Ceylon cinnamon (_cinnamomum zeylanicum_, Nees). - 2. Calumba root (_Jateorhiza palmata_, [Lam.] Miers). - 3. Dogwood root bark (_Cornus florida_, L.). - 4. Cubeb (_Piper cubeba_, L., f.) - 5. Echinacea (_Echinacea angustifolia_, D.C.).] - -[Illustration: PLATE 34 - - 1. Saigon cinnamon. - 2. Ruellia root (_Ruellia ciliosa_, Pursh.). - 3. Cascara sagrada (_Rhamnus purshiana_, D.C.). - 4. Saigon cinnamon.] - -The walls of all stone cells are composed of lignin. - -The form of stone cells varies greatly; in aconite the stone cells -are quadrangular; in ruellia they are rectangular; in pimenta, -they are circular or oval in outline; in most stone cells they are -polygonal. - -The lignified walls of stone cells are stained red with a solution of -phloroglucin and hydrochloric acid, and the walls are stained yellow -by aniline chloride. - - - ENDODERMAL CELLS - -The =endodermal cells= of the different plants vary greatly in form, -color, structure, and composition of the wall, yet these different -endodermal cells may be divided into two groups: first, thin-walled -parenchyma-like cells, and secondly, thick-walled fibre-like cells. -In the thin-walled endodermal cells the walls are composed of -cellulose, and the cell terminations are blunt or rounded. When the -drug is powdered, the cells break up into small diagnostic fragments. -In the thick-walled endodermal cells, the walls are lignified and -porous, and the ends of the cell are frequently pointed and resemble -fibres. - -Sarsaparilla root, triticum, convallaria, and aletris have -thick-walled endodermal cells. - - - STRUCTURE OF ENDODERMAL CELLS - -The endodermal cells of sarsaparilla root (Plate 35, Fig. 1) are -never more than one layer in thickness. The walls are porous and of -a yellowish-brown color. Alternating with the thick-walled cell is a -thin-walled cell, which is frequently referred to as a passage cell. - -The endodermal cells of triticum (Plate 35, Fig. 2) are yellowish, -and the walls are porous and striated. There are one or two layers -of cells. The cells forming the outer layer have very thin outer but -thick inner walls, while the cells forming the inner layer are more -uniform in thickness. - -The endodermal cells of convallaria (Plate 35, Fig. 3) are yellowish -white in color, and the walls are porous and striated. The outer wall -of the layer of cells is thinner than the inner wall. The innermost -layer of cell is more uniformly thickened. - -[Illustration: PLATE 35 - - CROSS-SECTIONS OF ENDODERMAL CELLS OF - - 1. Sarsaparilla root (_Smilax officinalis_, Kunth). - 2. Triticum (_Agropyron repens_, L.). - 3. Convallaria (_Convallaria majalis_, L.). - 4. Aletris (_Aletris farinosa_, L.).] - -The endodermal cells of aletris (Plate 35, Fig. 4) are yellowish -brown, slightly porous and striated. There are one or two layers of -these cells, and two of the smaller cells usually occupy a space -similar to that occupied by the radically elongated single cell. - -On a longitudinal view, the endodermal cells of sarsaparilla -triticum, convallaria, and aletris appear as follows: - -Those of sarsaparilla (Plate 36, Fig. 1) are greatly elongated, the -ends of the cells are blunt or slightly pointed, and the walls appear -porous and striated. - -Those of triticum (Plate 36, Fig. 2) are elongated, the walls are -porous and striated, and the outer wall is much thinner than the -inner wall. The end wall between two cells frequently appears common -to the two cells. - -Those of convallaria (Plate 36, Fig. 3) are elongated, and the end -wall is usually blunt. The outer wall is thinner than the inner wall. - -Those of aletris (Plate 36, Fig. 4) are fibre-like in appearance; the -ends of the cells are pointed and the wall is strongly porous. The -longitudinal view of these cells is shown in plate 36. - - - HYPODERMAL CELLS - -=Hypodermal cells= occur in sarsaparilla root and in triticum. -In the cross-section of sarsaparilla root (Plate 37, Fig. 1) the -hypodermal cells are yellowish or yellowish brown. The outer wall is -thicker than the inner wall, and the cell cavity is mostly rounded, -and contains air. The walls are porous and finely striated. On -longitudinal view, the hypodermal cells of sarsaparilla (Plate 37, -Fig. 2) are greatly elongated, and the outer and side walls are -thicker than the inner walls. The ends of the cells are blunt and -distinct from each other. - -In cross-section, the hypodermal cells of triticum (Plate 37, Fig. 3) -are nearly rounded in outline, and the walls are of nearly uniform -thickness. In longitudinal view (Plate 37, Fig. 4) the same cells -appear parenchyma-like, and the walls between any two cells appear -common to the two cells. - -[Illustration: PLATE 36 - - LONGITUDINAL SECTIONS OF ENDODERMAL CELLS - - 1. Sarsaparilla root (_Smilax officinalis_, Kunth). - 2. Triticum (_Agropyron repens_, L.). - 3. Convallaria (_Convallaria majalis_, L.). - 4. Aletris (_Aletris farinosa_, L.).] - -[Illustration: PLATE 37 - - HYPODERMAL CELLS - - 1. Cross-section sarsaparilla root (_Smilax officinalis_, Kunth). - 2. Longitudinal section sarsaparilla root (_Smilax officinalis_, - Kunth). - 3. Cross-section triticum (_Agropyron repens_, L.). - 4. Longitudinal section triticum (_Agropyron repens_, L.).] - - - - - CHAPTER IV - - ABSORPTION TISSUE - - -Most plants obtain the greater part of their food, first, from the -soil in the form of a watery solution, and, secondly, from the air -in the form of a diffusible gas. In a few cases all food material is -obtained from the air, as in the case of epiphytic plants. In such -plants, the aerial roots have a modified outer layer--velamen--which -functions as a water-absorbing and gas-condensing tissue. Many -xerophytic plants absorb water through the trichomes of the leaf. -Such absorption tissue enables the plant to absorb any moisture that -may condense upon the leaf and that would not otherwise be available -to the plant. The water-absorbing tissue of roots is restricted to -the root hairs, which are found, with few exceptions, only on young -developing roots. - - - ROOT HAIRS - -=Root hairs= usually occur a short distance back of the root cap. -There is, in fact, a definite zone of the epidermis on which the root -hairs develop. This zone is progressive. As the root elongates the -root hairs continue to develop, the zone of hairs always remaining at -about the same distance from the root cap. With the development of -new zones of growth the hairs on the older zone die off and finally -become replaced by an epidermis, or a periderm, except in the case of -sarsaparilla root, and possibly other roots that have persistent root -hairs. - -Each root hair is an outgrowth from an epidermal cell (Plate 38, Fig. -3). The length of the hair and its form depend upon the nature of the -soil, whether loose or compact, and upon the amount of water present. - -A root hair is formed by the extension of the peripheral wall of -an epidermal cell. At first this wall is only slightly papillate, -but gradually the end wall is extended farther and farther from -the surface of the root, caused by the development of side walls by -the growing tip of the root hair until a tube-like structure, root -hair, is produced. The root hair is then a modified epidermal cell. -The protoplast lines the cell, and the central part of the root -hair consists of a large vacuole filled with cell sap. The wall of -the root hair is composed of cellulose, and the outermost part is -frequently mucilaginous. As the root hairs develop, they become bent, -twisted, and of unequal diameter, as a result of growing through -narrow, winding soil passages. During their growth, the root hairs -become firmly attached to the soil particles. The walls of root hairs -give an acid reaction caused by the solution of the carbon dioxide -excreted by the root hair. The acid character of the wall attracts -moisture, and in addition has a solvent action on the insoluble -compounds contained in the soil. It will thus be seen that the method -of growth, structure, composition, and reaction of the wall of the -root hair is perfectly suited to carry on the work of absorbing the -enormous quantities of water needed by the growing plant. It is -a well-known fact that when two solutions of unequal density are -separated by a permeable membrane, the less dense liquid will pass -through the membrane to the denser liquid. The wall of the root hair -acts like an osmotic membrane. The less dense watery solution outside -the root hair passes through its wall and into the denser cell sap -solution. As the solution is absorbed, it passes from the root hair -into the adjoining cortical parenchyma cells. - -It is a fact that root hairs are seldom found in abundance on -medicinal roots. This is due to the fact that root hairs occur -only on the smaller branches of the root, and that when the root -is pulled from the ground the smaller roots with their root hairs -are broken off and left in the soil. For this reason a knowledge of -the structure of root hairs is of minor importance in the study of -powdered drugs. An occasional root hair is found, however, in most -powdered roots, but root hairs have little or no diagnostic value, -except in false unicorn root and sarsaparilla. When false unicorn -root is collected, most of the root hairs remain attached to the -numerous small fibrous roots, owing to the fact that these roots are -easily removed from the sandy soil in which the plants grow. The -root hairs of false unicorn are so abundant and so large that they -form dense mats, which are readily seen without magnification. These -hairs are, therefore, macroscopically as well as microscopically -diagnostic. The root hairs of false unicorn (Plate 39, Fig. 2) have -white, wavy, often decidedly indented walls. The terminal, or end -wall, is rounded and much thicker than the side walls. - -[Illustration: PLATE 38 - - CROSS-SECTION OF SARSAPARILLA ROOT (_Smilax officinalis_, Kunth) - - 1. Epidermal cell developing into a root hair. - 2. Developing root hair. - 3. Nearly mature root hair. - 4. Hypodermal cells.] - -[Illustration: PLATE 39 - - ROOT HAIRS (Fragments) - - 1. Sarsaparilla root (_Smilax officinalis_, Kunth). - 2. False unicorn root (_Helonias bullata_, L.).] - -In sarsaparilla (Plate 39, Fig. 1) the root hairs are curved and -twisted. The end wall is thicker than the side walls. In some hairs -the walls are as thick as the walls of the thin-walled bast fibres. -This accounts for the fact that the root hairs are persistent on -even the older portions of sarsaparilla root, and it serves also to -explain why these root hairs remain on the root even after being -pulled from the firmly packed earth in which the root grows. - - - WATER ABSORPTION BY LEAVES - -In many xerophytic terrestrial plants, the trichomes occurring on -leaves act as a water-absorbing tissue. In such plants the walls -of the hairs are composed largely of cellulose. It is obvious that -these hairs absorb the water of condensation caused by dew and light -rains--water which could not reach the plant except by such means. - -There is no special tissue set aside for the absorption of gases from -the air. Carbon dioxide, which contributes the element carbon to the -starch formed by photosynthesis, enters the leaf by way of the stoma -and lenticels. The structure and the chief functions of these will be -considered under aërating tissue. - - - - - CHAPTER V - - CONDUCTING TISSUE - -All cells of which the primary or secondary function is that -of conduction are included under conducting tissue. It will be -understood how important the conducting tissue is when the enormous -quantity of water absorbed by a plant during a growing season is -considered. It will then be realized that the conducting system must -be highly developed in order to transport this water from one organ -to another, and, in fact, to all the cells of the plant. Special -attention must be given to the occurrence, the structure, the -direction of conduction, and to the nature of the conducted material. - -The cells or cell groups comprising the conducting tissue are vessels -and tracheids, sieve tubes, medullary ray cells, latex tubes, and -parenchyma. - - - VESSELS - -=Vessels= and =tracheids= form the principal upward conducting tissue -of plants. They receive the soil water expressed from the cortical -parenchyma cells located in the region of the root, immediately -back of the root hair zone. This soil water, with dissolved crude -inorganic and organic food materials, after entering the vessels -and tracheids passes up the stem. The cells needing water at the -different heights absorb it from the vessels, the excess finally -reaching the leaves. When the stem branches, the water passes into -the vessels of the branches and finally to the leaves of the branch. -In certain special cases the vessels conduct upward soluble food -material. In spring sugary sap flows upward through the vessels of -the sugar maple. - -Vessels are tubes, often of great length, formed from a number of -superimposed cells, in which the end walls have become absorbed. -The vessels therefore offer little resistance to the transference -of water from the roots to the leaves of a plant. The combined -length of the vessels is about equal to the height of the plant in -which they occur. The length of the individual vessels varies from a -fraction of a meter up to several meters. - - - ANNULAR VESSELS - -The =annular vessels= are thickened at intervals in the form of rings -(Plate 40, Fig. 1), which extend outward from and around the inner -wall of the vessel. In fact, it is the inner wall which is thickened -in all the different types of vessels. The ring-like thickening -usually separates from the wall when the drug is powdered. Such -separated rings occur frequently in powdered digitalis, belladonna, -and stramonium leaves. Annular vessels are not, however, of -diagnostic importance, because more characteristic cells are found in -the plants in which they occur. Not infrequently a vessel will have -annular thickenings at one end and spiral thickenings at the other. -Such vessels are found in the pumpkin stem (Plate 40, Fig. 1). - -Vessels are distinguished from other cells by their arrangement, by -their large size when seen in cross-section, and by the thickening -of the wall when seen in longitudinal sections of the plant or in -powders. The side walls of vessels are thickened in a number of -striking yet uniform ways. The chief types of thickening of the wall, -beginning with one that is the least thickened, are annular, spiral, -sclariform, pitted, and pitted with bordered pores. - - - SPIRAL VESSELS - -In the =spiral vessel= the thickening occurs in the form of a -spiral, which is readily separated from the side walls. This is -particularly the case in powdered drugs, where the spiral thickening -so frequently separates from the cell wall. There are three types of -spiral vessels: those with one (Plate 41, Fig. 1), those with two, -and those with three spirals. Single spirals occur in most leaves; -double spirals occur in many plants (Plate 41, Fig. 2), but they -are particularly striking in powdered squills. Triple spirals are -characteristic of the eucalyptus leaf (Plate 41, Fig. 3); in fact, -they form a diagnostic feature of the powder. Frequently a spirally -thickened wall indicates a developmental stage of the vessel. Many -such vessels are spirally thickened at first, but later, when -mature, an increased amount of thickening occurs and the vessel -becomes a reticulate or pitted vessel. Many mature vessels, however, -are spirally thickened as indicated above. In herbaceous stems and -in certain roots and leaves spiral vessels are associated with the -sclariform reticulate and pitted type. In certain cases a single -spiral band will branch as the vessel matures. - -There is a great variation in the amount of spiral thickening -occurring in a vessel. In leaves, particularly, the spiral appears -loosely coiled; while in squills and other rhizomes and roots the -spiral appears as a series of rings. When viewed by high power only -half of each spiral band is visible. At either side of the cell the -exact size and form of the thickening appear in two parallel rows of -dark circles or projections from the walls. This thickening of the -wall is rendered visible from the fact that the light is retarded as -it passes through that portion of the spiral extending from the upper -to the under side of the spiral; while the light readily traverses -the upper and lower cross bands of the vessel. - -It should be remembered that, when the upper part of the spiral -vessel is in focus, the bands appear to bend in a direction away from -the eye; while when the under side of the bands are in focus, the -bands appear to bend toward the eye. These facts will show that it -is necessary to focus on both the upper and lower walls in studying -spiral vessels. In double spiral vessels the spirals are frequently -coiled in opposite directions; therefore the bands appear to cross -one another. In eucalyptus leaf the three bands are coiled in the -same direction. In all cases the thickening occurs on all sides of -the wall. Its appearance will, therefore, be the same no matter at -what angle the vessel is viewed. - - - SCLARIFORM VESSELS - -=Sclariform vessels= have interrupted bands of thickening on the -inner walls. Two or more such bands occur between the two side walls. -The series of bands are separated by uniformly thickened portions of -the wall extending parallel to the length of the vessel. Sclariform -vessels are usually quite broad, so that it is necessary to change -the focus several times in order to bring the different series of -bands in focus. The series of bands are usually of unequal width and -length. - -[Illustration: PLATE 40 - - ANNULAR AND SPIRAL VESSELS - - 1. Pumpkin stem (_Cucurbita pepo_, L.). - 2. Two characteristic views of spiral vessels. - 3. (_A_) Upper part of spiral vessel in focus. - (_B_) Under part of spiral vessel in focus. - 4. Spiral vessel of the disk petal matricaria (_Matricaria - chamomilla_, L.).] - -[Illustration: PLATE 41 - -SPIRAL VESSELS - - 1. Single spiral vessel of pumpkin stem (_Cucurbita pepo_, L.). - 2. Double spiral vessel of squill bulb (_Urginea maritima_, [L.] - Baker). - 3. Triple spiral vessel of eucalyptus leaf (_Eucalyptus globulus_, - Labill).] - -Sclariform vessels occur in male fern (Plate 42, Fig. 2), calamus, -tonga root (Plate 42, Fig. 3), and sarsaparilla (Plate 42, Fig. 1). -In each they are characteristic. Sclariform vessels, with these few -exceptions, do not occur in drug plants. In fact, drugs derived from -dicotyledones rarely have sclariform vessels. They occur chiefly -in the ferns and drugs derived from monocotyledenous plants. Their -presence or absence should, therefore, be noted when studying -powdered drugs. - - - RETICULATE VESSELS - -=Reticulate vessels= are of common occurrence in medicinal plants. In -fact, they occur more frequently than any other type of vessel. The -basic structure of reticulate vessels (Plate 43, Fig. 1) occurring in -different plants is similar, but they vary in a recognizable way in -different plants (Plate 43, Fig. 2). The walls of reticulate vessels -are thickened to a greater extent than are the walls of spirally -thickened vessels. - - - PITTED VESSELS - -=Pitted vessels= are met with most frequently in woods and -wood-stemmed herbs. There are two distinct types of pitted -vessels--_i.e._, simple pitted vessels and pitted vessels with -bordered pores. - -The pitted vessel represents the highest type of cell-wall -thickening. The entire wall of the vessel is thickened, with the -exception of the places where the pits occur. The number and size of -the pits vary greatly in different drugs. In quassia (Plate 44, Fig. -1) the pits are numerous and very small, and the openings are nearly -circular in outline. In white sandalwood (Plate 44, Fig. 3). the pits -are few in number, but when they do occur they are much larger than -are the pits of quassia. - - - PITTED VESSELS WITH BORDERED PORES - -=Pitted vessels with bordered pores= are of common occurrence in the -woody stems and stems of many herbaceous plants (Plate 45, Figs. 3 -and 4). In such vessels the wall is unthickened for a short distance -around the pits. This unthickened portion may be either circular or -angled in outline, a given form being constant to the plant in which -it occurs. The pits vary from oval to circular. Pitted vessels with -bordered pores occur in belladonna and aconite stems. - -[Illustration: PLATE 42 - - SCLARIFORM VESSELS - - 1. Sarsaparilla root (_Smilax officinalis_, Kunth). - 2. Male fern (_Dryopteris marginalis_, [L.] A. Gray). - 3. Tonga root.] - -[Illustration: PLATE 43 - - RETICULATE VESSELS - - 1. Hydrastis rhizome (_Hydrastis canadensis_, L.). - 2. Musk root (_Ferula sumbul_, [Kauffm.] Hook., f.).] - -[Illustration: PLATE 44 - - PITTED VESSELS - - 1. Quassia, low magnification (_Picræna excelsa_, [Swartz] Lindl.). - 2. Quassia, high magnification. - 3. White sandalwood (_Santalum album_, L.).] - -[Illustration: PLATE 45 - - VESSELS - - 1. Reticulate vessel of calumba root (_Jateorhiza palmata_, [Lam.] - Miers). - 2. Reticulate tracheid of hydrastis rhizome (_Hydrastis - canadensis_, L.). - 3. Pitted vessel with bordered pores of belladonna stem. - 4. Pitted vessel with bordered pores of aconite stem (_Aconitum - napellus_, L.).] - -Vessels and tracheids lose their living-cell contents when fully -developed. In the vessels the cell contents disappear at the period -of dissolution of the cell wall. - -The walls of vessels and tracheids are composed of lignin, a -substance which prevents the collapsing of the walls when the -surrounding cells press upon them, and which also prevents the -tearing apart of the wall when the vessel is filled with ascending -liquids under great pressure. Lignin thus enables the vessel to -resist successively compression and tearing forces. - -Tracheids are formed from superimposed cells with oblique perforated -end walls. The side walls of tracheids are thickened in a manner -similar to those of vessels. The tracheids in golden seal are of a -bright-yellow color, and groups of these short tracheids scattered -throughout the field form the most characteristic part of the -powdered drug. In ipecac root the tracheids are of a porcelain-white, -translucent appearance, and they are much longer than are the -tracheids of golden seal. - -The cellulose walls of parenchyma cells are stained blue with -hæmatoxylin and by chlorzinciodide. Cellulose is completely soluble -in a fresh copper ammonia solution. - - - SIEVE TUBES - -=Sieve tubes= are downward-conducting cells. They conduct downward -proteid food material. This fact is easily demonstrated by adding -iodine to a section containing sieve tubes, in which case the sieve -tubes are turned yellow. - -Developing sieve tubes have all the parts common to a living cell; -but when fully mature, however, the nucleus becomes disorganized, but -a layer of protoplasm continues to line the cell wall. - -Sieve tubes (Plate 46, Fig. 1) are composed of a great number of -superimposed cells with perforated end walls and with non-porous -cellulose side walls. The end walls of two adjoining cells are -greatly thickened and the pores pass through both walls. This -thickened part of the porous end walls of two sieve cells is called -the sieve plate, and it may be placed in an oblique or a horizontal -position. - -[Illustration: PLATE 46 - - 1. Longitudinal section of sieve tube (_Cucurbita pepo_, L.). - 2. Cross-section of sieve tube just above an end wall--sieve plate.] - -In a longitudinal section the sieve tubes are seen to be slightly -bulging at the sieve plate, and through the pores extend protoplasmic -strands. The strands are united on the upper and lower side of -the sieve plate to form the protoplasmic strands of the living -sieve tubes and the callus, layers of dried plants. This callus is -frequently yellowish in color, and in all cases is separated from the -cell wall. In certain plants the sieve plate occurs on the side walls -of the sieve tubes in contact with other sieve tubes. - - - SIEVE PLATE - -=Sieve plates= on cross-section (Plate 46, Fig. 2) are polygonal -in outline, and the pores are either round or angled. Large sieve -tubes and sieve plates occur in pumpkin stem; but, almost without -exception, in drug plants the sieve tubes are small and the sieve -plate is inconspicuous. When the drug is powdered, the sieve tubes -break up into undiagnostic fragments. When studying sections of the -plants, the extent, size, and arrangement of the sieve tubes must -always be noted. - - - MEDULLARY BUNDLES, RAYS, AND CELLS - - Function - -The medullary ray cells are the lateral conducting cells of the -plant. They conduct outwardly the water and inorganic salts brought -up from the roots by the vessels and tracheids; and they conduct -inwardly toward the centre of the stem the food material manufactured -in the leaves and brought down by the sieve cells. The medullary rays -thus distribute the inorganic and organic food to the living cells of -the plant, and they conduct the reserve food material to the storage -cells, and, lastly, they function in certain plants as storage cells. - - - Occurrence - -The form, size, wall structure, and the distribution of the medullary -ray bundles, rays, and cells are best ascertained by studying: -first, the cross-section of the plant; secondly, the radial section; -and, thirdly, the tangential section. - -Students should be careful to distinguish between the medullary ray -bundle, the medullary ray, and the medullary ray cell. In some plants -the bundles are only one cell wide, but in other plants the medullary -ray bundle is more than one cell wide, frequently several cells wide. - - - THE MEDULLARY RAY BUNDLE - -The =medullary ray bundle= is made up of a great many medullary ray -cells. These bundles (Plate 106, Fig. 5) are of variable length, -height, and width. The bundles are isolated, and they occur among -and separate the other cells of the plants in which they occur. -Tangential sections show the medullary ray bundle in cross-section. -Such sections are lens-shaped, and they show both the width and the -height of the medullary ray bundle. The length of the medullary ray -bundle is shown in cross-sections. - - - THE MEDULLARY RAY - -The =medullary ray= (Plate 47) is a term used to indicate that part -of a medullary ray bundle which is seen in cross-sections and in -radial sections. In cross-sections the length of the ray will be as -great as the length of the bundle, and the width of the ray will be -as great as the width of the medullary ray bundle at the point cut -across. In longitudinal sections the medullary ray will differ in -height according to the thickness of the bundle at the point cut. - -When the medullary rays extend from the centre of the stem to the -middle bark, they are termed primary medullary rays; when they extend -from the cambium circle to the middle bark, they are termed secondary -medullary rays. As the plant grows, the diameter of the organ becomes -greater and the number of medullary rays are increased. In each of -these cases the medullary rays may be one or more than one cell wide, -according to whether the medullary ray bundle is one or more than one -cell wide. Even in the same plant the width of the medullary rays -will vary if the bundle is more than one cell wide, according to -width of the medullary ray bundle at the point cut across. - -[Illustration: PLATE 47 - - RADIAL LONGITUDINAL SECTION OF WHITE SANDALWOOD - (_Santalum album_, L.) - - 1. Medullary ray. - 2. Wood fibres and wood parenchyma.] - -On cross-section the medullary rays are seen to vary greatly. In many -plants they are more or less straight radial lines, as in quassia -(Plate 105, Fig. 2); while in other plants they form wavy lines -where they bend or curve around the conducting cells, as in piper -methysticum, kava-kava (Plate 48, Fig. A). - -In the study of powdered drugs the radial view of the medullary rays -is most frequently seen. - -In a perfect radial section (Plate 107, Fig. 2) the medullary rays -are seen as tiers of cells in contact throughout their long diameter, -and they run at right angles to the long diameter of the other cells. -This view of the rays shows the length and height of the medullary -ray. In logwood the rays are often forty cells high. In powdered -barks, woods (Plate 47), and woody roots the radial view of the -medullary rays is frequently diagnostic. - -In guaiacum officianale wood the medullary rays are one cell wide on -cross-section, and up to six cells high on the tangential section. -In santalum album the rays are from one to three cells wide on -cross-section, and up to six cells high on tangential section. In the -greater number of plants the rays are more than one cell wide. - - - THE MEDULLARY RAY CELL - -The =medullary ray cell= (Plate 48, Fig. 1) is one of the individual -cells making up the medullary ray bundle and the medullary ray. - -The cross-sections of the cells which are seen in tangential sections -show the cells to be mostly circular in outline when they occur in -the central portion of medullary ray bundles of more than two cells -in width; but they are more irregular in outline when the medullary -ray bundle is only one cell wide. Even the cells of the three or more -cell-wide bundles have irregular, outlined cells at the ends of the -bundle and on the sides in contact with the other tissues. - -The length and height of the medullary ray cell are shown in radial -sections; while the width and length of the medullary ray cells are -shown in cross-sections. - - - Structure of Cells - -The structure of the individual cells forming the medullary rays -differs greatly in different plants, but is more or less constant in -structure in a given species. - -The medullary rays of the wood usually have strongly pitted side and -end walls, while the medullary rays of most barks are not at all, or -only slightly, pitted. In most plants the cells are of nearly uniform -size. Frequently, however, the cells vary in size in a given ray, as -shown in the cross-section of kava-kava. - - - Arrangement of the Cells in a Ray - -The union of any two cells in a ray is also of importance. In -quassia the medullary ray cells have oblique end walls, so that on -cross-section the line of union between two cells is an oblique -wall. In most plants the medullary ray cells have blunt or square or -oblique end walls, so that the line of union is a straight line. - -In most plants the cells are much longer than broad, but the cells of -sassafras bark are nearly as broad as long. - -The walls of the cortical medullary ray cells and the medullary rays -of most roots and stems of herbs are composed of cellulose; while -the walls of medullary ray cells occurring in woods are frequently -lignified. - -There is a great variation in the character of the cell contents of -medullary rays. In white pine bark (Plate 48, Fig. B1) are deposits -of tannin; in quassia wood, starch; in canella alba, rosette crystals -of calcium oxalate, etc. - - - LATEX TUBES - -Living =latex tubes=, like sieve tubes, have a layer of protoplasm -lining the walls, and, in addition, have numerous nuclei. In drug -plants the nuclei are not distinguishable, but the protoplasm is -always clearly discernible. - -[Illustration: PLATE 48 - - _A._ Cross-section of kava-kava root (_Piper methysticum_, - Forst., f.). - 1. Unequal diameter medullary ray cells. - 2. Vessels. - 3. Wood parenchyma. - 4. Wood fibres. - - _B._ Cross-section of white pine bark (_Pinus strobus_, L.). - 1. Wavy medullary rays with tannin. - 2. Parenchyma cells. - 3. Sieve cells.] - -Latex tubes function both as storage and as conducting cells. They, -like the sieve tubes, contain proteid substances chiefly, yet -frequently starch is found. The cells bordering the latex tubes -absorb from them, as needed, the soluble food material. While our -knowledge concerning the function of latex in some plants is meagre, -still in other plants it is practically certain that the latex is -composed of nutritive substances which are utilized by the plant as -food. In certain other plants the latex appears to be used as a means -of resisting insect attacks and as a protection against injury. - -There are two types of latex tubes common to plants, namely, latex -cells and latex vessels. Latex tubes developing from a single cell do -not differ materially from a latex tube originating from the fusion -of several cells. In each case the latex tube branches to such an -extent that it bears no resemblance to ordinary cells. It would seem -that the ultimate branches are formed and develop in much the same -manner as root hairs--that is, by a growing tip of the branch. A -mature plant may therefore have latex tubes with almost numberless -branches (Plate 50, Fig. 1) and be of very great length. - -The branches of latex tubes develop in such an irregular manner that -it is possible to obtain a cross and a longitudinal section of the -latex tubes by making a cross-section of stem. Such a section is -shown in the drawing of the cross-section of the rhizome of black -Indian hemp (Plate 49, Fig. B). - -The color of the latex in medicinal plants varies from a gray white -in papaw (carica papaya), aromatic sumac, black Indian hemp, and -bitter root, to white in the opium poppy, light orange in celandine, -and deep orange in bloodroot (Plate 50, Fig. 2). In each of these -cases it is the latex which yields the important medicinal products. - - - PARENCHYMA - -The larger amount of plant tissue is composed of =parenchyma= cells. -These cells vary from square to oblong, or they may be irregular and -branched. The end walls are square or blunt, and the wall is composed -of cellulose, with the exception of the wood parenchyma, which has -lignified walls. - -There are seven characteristic types of parenchyma cells: (1) -cortical parenchyma, (2) pith parenchyma, (3) wood parenchyma, -(4) leaf parenchyma, (5) aquatic plant parenchyma, (6) endosperm -parenchyma, (7) phloem parenchyma. - -[Illustration: PLATE 49 - - _A._ Cross-section of black Indian hemp (_Apocynum cannabinum_, L.). - 1. Longitudinal section of a latex tube. - 2. Cross-section of latex tube. - 3. Parenchyma. - - _B._ Cross-section of a part of black Indian hemp root. - 4. Cross-section of a large latex tube. - 5. Parenchyma.] - -[Illustration: PLATE 50 - - LATEX VESSELS - - 1. Radial-longitudinal section of dandelion root (_Taraxacum - officinale_, Weber). - 2. Cross-section of sanguinaria root (_Sanguinaria canadensis_, L.). - 3. Cross-section of dandelion root.] - -Parenchyma cells, cortical, pith, aquatic plant, leaf, flower, -and endosperm, conduct in all directions--upward, downward, and -laterally. The direction of conduction depends upon the needs of the -different cells forming the plant. The fluids pass from the cell with -an abundance of cell sap to the cell with less cell sap. In this wall -all cells are provided with food. - -Parenchyma cells conduct water absorbed by the roots and soluble -carbohydrate material chiefly. - -The walls of all the different types of parenchyma cells are composed -of cellulose with the exception of the wood parenchyma cells, -the walls of which are lignified. The end walls of non-branched -parenchyma cells and the cell terminations of branched cells are very -blunt. - - - CORTICAL PARENCHYMA - -=Cortical parenchyma= (Plate 51) differs greatly in size, thickness -of the walls, and arrangement. A study of the longitudinal sections -of different parts of medicinal plants reveals the fact that the -cortical parenchyma cells form superimposed layers in which the end -walls are either parallel, in which case the arrangement resembles -that of several rows of boxes standing on end, or the end walls of -the cells alternate with each other, in which case the arrangement is -similar to that of the arrangement of the bricks in a building. - -In certain plants the cortical parenchyma cells are long and narrow -and rectangular in shape, while in other plants the cells, although -still rectangular in outline, are very broad and approach the square -form. - -All typical cortical parenchyma cells have uniformly thickened -non-pitted walls. In most barks the parenchyma cells beneath the -bark are elongated tangentially, but are very narrow radially. The -cells are always arranged around intercellular spaces, which vary -from triangular, quadrangular, etc., according to the number of cells -bordering the intercellular space. - - - PITH PARENCHYMA - -=Pith parenchyma= (Plate 52) differs from cortical parenchyma cells -chiefly in the character of the walls, which are usually thicker and -always pitted. - -[Illustration: PLATE 51 - - PARENCHYMA CELLS - - 1. Longitudinal section of the cortical parenchyma of celandine - root (_Chelidonium majus_, L.) 2. Cross-section of the cortical - parenchyma of sarsaparilla root (_Smilax officinalis_, Kunth).] - -[Illustration: PLATE 52 - - _A._ Longitudinal section of the pith parenchyma of grindelia stem - (_Grindelia squarrosa_, [Pursh] Dunal). - 1. Cell cavity. - 2. Cross-section of the porous end wall. - 3. Surface view of the porous side wall. - _B._ Cross-section of the pith parenchyma of grindelia stem. - 1. Cell cavity. - 2. Porous walls. - 3. Pitted end walls.] - - - LEAF PARENCHYMA - -The =parenchyma cells= (Plate 109, Fig. 1) of leaves, of flower -petals, and the parenchyma cells of some aquatic plants are branched; -that is, each cell has more than two cell terminations. These cell -terminations are frequently quite attenuated and usually very blunt. -Such a cell structure provides for a greater amount of intercellular -space and a maximum exposure of surface. This arrangement makes it -possible for the parenchyma cells of the leaf to absorb more readily -the enormous amount of carbon dioxide needed in the photosynthetic -process. - - - AQUATIC PLANT PARENCHYMA - -The =parenchyma of aquatic plants= (Plate 59) has large intercellular -spaces formed by the chains of cells. - - - WOOD PARENCHYMA - -=Wood parenchyma= (Plate 105, Fig. 3) cells are the narrowest -parenchyma cells occurring in the plant. Their walls are always -lignified and strongly pitted, and in some cases the end walls common -to two cells are obliquely placed. - - - PHLOEM PARENCHYMA - -=Phloem parenchyma= (Plate 100, Fig. 8) cells are usually associated -with sieve cells. They are very long, narrow, and have thin, -non-pitted walls. The thinness of the walls undoubtedly enables the -cells to conduct diffusible food substance more quickly than the -cortical parenchyma cells. - - - PALISADE PARENCHYMA - -=Palisade parenchyma= of leaves is of the typical parenchyma shape -and the end walls are placed nearly on a plane, even when more than -one layer is present. The cells are very small, however, and the -walls are very thin and non-pitted. - - - - - CHAPTER VI - - AERATING TISSUE - - -The =aerating tissue= of the plant performs a threefold function: -first, it permits the exchange of gases during photosynthesis; -secondly, it permits the entrance of oxygen and the exit of carbon -dioxide during respiration; and, thirdly, it permits the exit of the -excess of water absorbed by the plant. - -The above functions are carried on by the stomata, the water-pores, -the lenticels, and the intercellular spaces of the plant. The stoma -functions as the chief channel for the passage of CO₂-laden air into -the leaf and of oxygen-laden air from the leaf to the atmosphere. The -stoma also functions as an organ of transpiration, since through the -stoma a large part of the excess water of the plant passes off into -the air. - - - WATER-PORES - -In certain plants the primary epidermis is provided with openings -resembling stomata, but unlike stomata the orifice remains open, and -instead of being located on the upper or lower surface of the leaf, -they are located on the margin of leaves immediately outward from the -veins. Water is given off to the atmosphere from these openings. Such -an opening is usually designated as a water-pore. - - - STOMATA - -The chief external openings of the epidermis of leaves, of herbs, and -of young wood stems are known as stomata. Surrounding the stoma are -two cells known as guard cells. - -=Guard cells= differ greatly in form, in size, in arrangement, in -occurrence, in association, in abundance (Plates 53, 54, and 55), and -in color. The guard cells surrounding the stoma vary in form from -circular to lens-shaped. In most leaves the outline of the guard -cells is rounded or has a curved outline; but in a few cases the -guard cells have angled outlines. - -[Illustration: PLATE 53 - - 1. Stoma and surrounding cells of aconite stem (_Aconitum - napellus_, L.). - - 2. Stoma and angled striated walled surrounding cells of peppermint - stem (_Mentha piperita_, L.). 3. Stoma and elongated surrounding - cells of lobelia stem (_Lobelia inflata_, L.).] - -[Illustration: PLATE 54 - - TYPES OF STOMA - - 1. Under epidermis of short buchu (_Barosma betulina_, [Berg.] - Bartling and Wendl., f.) showing stoma and deposits of hesperidin. - - 2. Under epidermis of Alexandria senna (_Cassia acutifolia_, - Delile) showing stoma and thick-angled walled surrounding cells. - - 3. Upper epidermis of eucalyptus leaf (_Eucalyptus globulus_, - Labill.) showing sunken stoma and slightly beaded walled - surrounding cells. - - 4. Under epidermis of belladonna leaf (_Atropa belladonna_, L.) - showing stoma and wavy, striated, walled epidermal cells.] - -The =arrangement of the surrounding cells= of the stoma is one of the -most important characteristics of the different leaves. As a rule the -number of surrounding cells about a stoma is constant for a given -species. In senna leaves (Plate 54, Fig. 2) there are normally two -surrounding cells about each guard cell, while in coca there are four -(Plate 55, Fig. 1). In senna the long diameter of the surrounding -cells is parallel to the long diameter of the guard cells; but in -coca the long diameter of two surrounding cells is at right angles to -the long diameter of the guard cells, while two cells are parallel to -the long diameter of the guard cells. - -In most leaves there are more than two cells around the guard cells. - -The form and size of the surrounding cells must always be considered. -In most leaves they are variable in size and form. - -Guard cells occur first, even with the surface of the leaf (Plate 56, -Fig. A); secondly, above the surface of the leaf (Plate 56, Fig. B); -and, thirdly, below the surface of the leaf. (Plate 56, Fig. C). Only -one of the above types occurs in a given species of plant. That is, -plants with stomata above the surface of the leaf do not have stomata -on a level with or below the leaf surface. - -The number of stomata on a given surface of a different leaf varies -considerably. - -In many of the medicinal leaves stomata occur only on the under -surface of the leaf. In other leaves stomata occur on both surfaces -of the leaf; but in such cases there are a greater number on the -under surface. - -In certain leaves the long diameter of the guard cells is parallel to -the length of the leaf; in other cases the long diameter of the stoma -is arranged at right angles to the length of the leaf. - -In other leaves the arrangement is still more irregular, the guard -cells assuming all sorts of positions in relation to the length of -the leaf. - -[Illustration: PLATE 55 - - LEAF EPIDERMI WITH STOMA - - 1. Under epidermis of coca leaf (_Erythroxylon coca_, Lam.) with - stoma on a level with the surface. - - 2. Under epidermis of false buchu (_Marrubium peregrinum_, L.) with - stoma below the level of the surface. - - 3. Upper epidermis of deer tongue (_Trilisa odoratissima_, [Walt.] - Cass.) with stoma above the leaf surface.] - -[Illustration: PLATE 56 - - _A._ Cross-section of belladonna leaf (_Atropa belladonna_, L.). - 1, Epidermal cells; 2, Guard cells even with the leaf surface; 3, - Surrounding cells; 4, Air space below the guard cells; 5, Palisade - cells; 6, Mesophyll cells. _B._ Cross-section of deer tongue leaf, - 1. Epidermal cells; 2, Guard cells above the surface of the leaf; - 3, Surrounding cells; 4, Air space below the guard cells; 5, - Hypodermal cells. _C._ Cross-section of white pine leaf (_Pinus - strobus_, L.). 1, Epidermal and hypodermal cells; 2, Guard cells - below the leaf surface; 3, Surrounding cells; 4, Air space below - the guard cells; 5, Parenchyma cells with projecting inner walls.] - -The =relation of the stoma to surrounding cells= is best shown in -cross-sections of the leaf. In powders the relationship of the stoma -to the surrounding cells is, however, readily ascertained. If the -guard cells come in focus first, they are above the surface; if the -guard cells and the surrounding cells come in focus at the same time, -the stomata are even with the surface; if the stomata come in focus -after the surrounding cells, they are below the surface of the leaf. -The relationship of the stoma to the surrounding cells should always -be ascertained, not only in cross-sections of the leaf, but also in -powders. - -There is the greatest possible variation in the size of guard cells. -This fact must always be kept in mind when studying leaves. This -variation in the size of the guard cells is clearly illustrated by -coca, senna, and by deer’s-tongue. In coca the stomata are very -small; in senna they are larger; while in deer’s-tongue the stomata -are very large. - -The width and length of the stoma or opening between the guard cells -are of a character which must not be overlooked. Generally speaking, -those leaves which have large guard cells will have correspondingly -large stomata. - -The guard cells usually contain chloroplasts showing various stages -of decomposition. - -In bay-rum leaf the guard cells are of a bright reddish-brown color, -but in most leaves the guard cells are colorless. - - - LENTICELS - -=Lenticels= are small openings occurring in the bark of plants. -The lenticels bear the same relationship to the stem that the -stomata do to the leaves. Lenticels, like stomata, have a threefold -function--namely, exchange of gases in photosynthesis, in -respiration, and the giving off of water. - -Lenticels are macroscopically as well as microscopically important. -When unmagnified the lenticels are circular, lens-shaped, or -irregular in outline. They are arranged in parallel longitudinal -lines or parallel transverse lines, or they are irregularly -scattered. The latter is the usual arrangement. In most cases they -are elevated slightly above the surface of the bark. In root barks -particularly the lenticels stand out prominently from the surface of -the bark and in many cases appear stalked. - -The color of the lenticels differs greatly in the different plants. -In acer spicatium they are brown; in witch-hazel they are gray; in -xanthoxylium they are yellowish; and lastly, the number of lenticels -occurring in a given surface of the bark should always be considered. - -On cross-sections the lenticel (Plate 57, Fig. 2) is seen to have -a central depressed portion made up of loosely arranged cells. -Bordering the cavity are typical cork cells. The cork cells -immediately surrounding the lenticels are usually darker in color, -and many of the cells are partly broken down. - -The size of lenticels will vary according to the type of the -lenticel. In studying sections more attention should be paid to the -character of the cells forming the lenticels than to the size of the -lenticel. - -On cross-section the intercellular spaces (Plate 58) are triangular, -quadrangular, or irregular. The spaces between equal diameter -parenchyma cells is triangular if three cells surround the space, and -quadrangular if four cells surround the space, etc. These spaces are -in direct contact with similar spaces that traverse the tissue at -right angles to its long axis. - -The branched mesophyll cells of the leaf and aquatic plant parenchyma -(Plate 59) are arranged around irregular cavities. In leaves and -aquatic plants these spaces run parallel to the long axis of the -organ. - -In each of the above cases the cavity is formed by the separation of -the cell walls. There is still another type of irregular cavities -which is formed by the dissolution or tearing apart of the cell -walls. Such cavities are found in the stems and roots of many herbs. - -The pith cells in the stems of many herbs become torn apart during -the growth of the stem, with the result that large irregular cavities -are formed. These cavities are usually filled with circulatory air. - -In the stems of conium, cicuta, angelica, and other larger herbaceous -stems the pith separates into layers. When a longitudinal section -is made of such a stem it is seen to be composed of alternating air -spaces and masses of pith parenchyma. - -The intercellular spaces are very large in leaves where enormous -quantities of carbon dioxide are vitalized in photosynthesis. - -[Illustration: PLATE 57 - - CROSS-SECTION OF ELDER BARK (_Sambucus canadensis_, L.). 1. - Periderm. 2. Lenticel. 3. Phellogen.] - -[Illustration: PLATE 58 - - INTERCELLULAR AIR SPACES - - _A._ Cross-section of uva-ursi leaf (_Arctostaphylos uva-ursi_, - [L.] Spreng.). - - 1. Irregular intercellular air spaces. - - _B._ Cross-section of the cortical parenchyma of sarsaparilla - root (_Smilax officinalis_, Kunth). 1, Triangular intercellular - spaces; 2, Quadrangular intercellular air spaces; 3, Pentagular - intercellular air spaces.] - -[Illustration: PLATE 59 - - IRREGULAR INTERCELLULAR AIR SPACES - - 1. Skunk-cabbage (_Symplocarpus fœtidus_, [L.] Nutt.) - 2. Calamus rhizome (_Acorus calamus_, L.).] - -In the rhizome of calamus and other aquatic plants the intercellular -spaces are very large. The cells of these plants are arranged in -the form of branching chains of cells which thus provide for large -intercellular spaces. - -The cells of the middle layer of flower petals, like the mesophyll of -leaves, is loosely arranged owing to the peculiar branching form of -the cells. - -Seeds and fruits contain, as a rule, few or no intercellular spaces. - - - - - CHAPTER VII - - SYNTHETIC TISSUE - - -Under synthetic tissue are grouped all tissues and cells which form -substances or compounds other than protoplasm. Such compounds are -stored either in special cavities or in the cells of the plant, as -the glandular hairs; internal secreting cavities of barks, stems, -leaves, fruits, seeds, and flowers; photosynthetic cells or cells -with chlorophyll, and the parenchymatic cells which form starch, -sugar, fats, alkaloids, etc. - - - PHOTOSYNTHETIC TISSUE - -The most important non-glandular synthetic tissue is the -photosynthetic tissue, which is composed of the chlorophyll-bearing -cells of the plant. These are the so-called green cells of leaves, of -stems of herbs, of young woody stems, and in the older woody stems of -plants like wild cherry, birch, etc. The greater part of the tissue -of leaves is composed of chlorophyll-bearing cells. - -Leaves collectively constitute the greatest synthetic manufacturing -plant in the world, because the green cells of the leaf produce most -of the food of men and animals. The two compounds utilized in the -manufacture of food are carbon dioxide (CO₂) and water (H₂O). These -two compounds are combined by chlorophyll through the agency of light -into starch. Chemically this reaction may be expressed as follows: - - 6CO₂ + 5H₂O = 2C₆H₁₀O₅ + 6O₂. - -During the day a large quantity of starch is formed. At night through -the action of a ferment the excess of starch remaining in the leaf -is converted into sugar (C₆H₁₂O₆) - C₆H₁₀O₅ + H₂O = C₆H₁₂O₆. In this -form it is distributed to the living cells of the plant. The presence -or absence of starch in leaves is easily ascertained by placing the -leaf in hot alcohol to remove the chlorophyll, and by adding Lugol’s -solution. If starch is present, the contents of the cells will become -bluish black; but if no starch is present, the cells remain colorless. - - - GLANDULAR TISSUE - -The =glandular tissue= of the plant is divided into two groups, -according to where it occurs. These groups are, first, =external= -glandular tissue, and secondly, =internal= glandular tissue. The most -important external glandular tissue is composed of the glandular -hairs. These are divided into two groups: first, =unicellular=; and -secondly, =multicellular= glandular hairs. - - - UNICELLULAR GLANDULAR HAIRS - -The =unicellular glandular hairs= are either sessile or stalked. - -=Sessile unicellular hairs= occur in digitalis leaves. - -=Stalked unicellular hairs= of digitalis are shown on Plate 60, Fig. -2. - -=Unicellular uniseriate stalked glandular hairs= occur on the stems -of the common house geranium (Plate 61, Fig. 2), on the leaves of -butternut, the leaves and stems of marrubium peregrinum (Plate 98, -Fig. 5), and in arnica flowers. The stalk varies from two to ten -cells; in eriodictyon the cells vary from four to eight cells. - -Unicellular multiseriate stalked glandular hairs are not of common -occurrence. - - - MULTICELLULAR GLANDULAR HAIRS - -=Multicellular glandular hairs= are divided into two groups: first, -sessile; and secondly, stalked hairs. - -Multicellular sessile glandular hairs occur on the leaves of -peppermint (Plate 60, Fig. 3), horehound (Plate 97, Fig. 7), and -in hops (Plate 60, Fig. 4). In each of these hairs there are eight -secretion cells. - -=Stalked glandular hairs= are divided into two groups: first, -uniseriate stalked; and secondly, multiseriate stalked glandular -hairs. - -=Multicellular uniseriate stalked glandular hairs= occur on the -leaves of tobacco (Plate 61, Fig. 4), belladonna (Plate 61, Fig. 1), -and digitalis (Plate 60, Fig. 2), and of the fruit of rhus glabra. - -[Illustration: PLATE 60 - - GLANDULAR HAIRS - - 1. Kamala (_Mallotus philippinensis_, [Lam.] [Muell.] Arg.). - 2. Digitalis leaf (_Digitalis purpurea_, L.). - 3. Peppermint leaf (_Mentha piperita_, L.). - 4. Lupulin. - 5. Cannabis indica leaf (_Cannabis saliva_, L.).] - -=Multicellular multiseriate stalked glandular hairs= occur on the -stems and leaves of cannabis indica (Plate 60, Fig. 5). - -In the glandular hair of kamala (Plate 60, Fig. 1) the number of -secretion cells is variable and papillate in form, and the cuticle is -separated from the secretion cells. - -In the glandular hair of hops the outer wall or cuticle is torn away -from the secretion cells, and the cavity thus formed serves as a -storage cavity. This distended cuticle of the hops shows the outline -of the cells from which it was separated. - -In the glandular hairs of the mints the secreted products (volatile -oils) are stored between the secretion cells and the outer detached -cuticle. This cuticle is elastic, and it becomes greatly distended as -the volatile oil increases in amount. - -In many of the so-called glandular hairs, tobacco, belladonna -geranium, etc., the synthetic products are retained in the glandular -cells, there being no special cavity for their storage. - -These hairs usually contain an abundance of chlorophyll. - -The division wall of multicellular glandular hairs may be vertical, -as in the two-celled hair of digitalis (Plate 60, Fig. 2); as in -horehound (Plate 97, Fig. 6), and as in peppermint (Plate 60, Fig. -3); in this case there are eight cells, and they form a more or less -flat plate of cells. - -In other hairs the division wall is horizontal; this produces a chain -of superimposed secreting cells, as in some of the glandular hairs of -belladonna leaf (Plate 61, Fig. 1), etc. - -In other hairs the division walls are both vertical and horizontal, -as in tobacco (Plate 61, Fig. 4), henbane (Plate 61, Fig. 3), -belladonna (Plate 61, Fig. 1). - -Other characters to be kept in mind in studying glandular hairs are -the following: Color of cell contents; size of the cells, whether -uniform or variable; character of wall, whether smooth or rough. - - - SECRETION CAVITIES - -=Secretion cavities= are divided into three groups, according to the -nature of the origin of the cavity: first, schizogenous cavities, -which originate by a separation of the walls of the secretion cells; -secondly, lysigenous cavities, which arise by the dissolution -of the walls of centrally located secretion cells; and thirdly, -schizo-lysigenous cavities, which originate schizogenously, but later -become lysigenous owing to the dissolution of the outer layers of the -secretion cells. - -[Illustration: PLATE 61 - - STALKED GLANDULAR HAIRS - - 1. Belladonna leaf (_Atropa belladonna_, L.). - 2. Geranium stem (_Geranium maculatum_, L.). - 3. Henbane leaf (_Hyoscyamus niger_, L.). - 4. Tobacco leaf (_Nicotiana tabacum_, L.).] - - - SCHIZOGENOUS CAVITIES - -=Schizogenous cavities= occur in white pine bark (Plate 62, Fig. -B). The cells lining the cavity are mostly tangentially elongated, -and the wall extends into the cavity in the form of a papillate -projection. Immediately back from these cells are two or three layers -of cells which resemble cortical parenchyma cells, except that they -are smaller and their walls are thinner. - -In white pine bark there is a single layer of thin-walled cells -lining the cavity. Immediately surrounding the secretion cells is a -single layer of thick-walled fibrous cells. - -In klip buchu (Plate 63, Fig. B), as in white pine leaf (Plate 64, -Fig. B), there is a single layer of thin-walled secretion cells which -are surrounded on three sides with parenchyma cells and on the outer -side by epidermal cells. - - - LYSIGENOUS CAVITIES - -=Lysigenous cavities= occur on the rind of citrus fruits--bitter and -sweet orange, lemon, grapefruit, lime, etc., and in the leaves of -garden rue, etc. - -In bitter orange peel, (Plate 64, Fig. A) the cavity is very -large, and the cells bordering the cavity are broken and partially -dissolved. The entire cells back of these are white, thin-walled, -tangentially elongated cells. There is a great variation in the size -of these cavities, the smaller cavities being the recently formed -cavities. - - - SCHIZO-LYSIGENOUS CAVITIES - -=Schizo-lysigenous= cavities are formed in white pine bark and many -other plants owing to the increase in diameter of the stem. In such -cases the walls of the secreting cells break down. The resulting -cavity resembles lysigenous cavities. - -=Unicellular secretion cavities= occur in ginger, aloe, calamus, and -in canella alba barb. - -[Illustration: PLATE 62 - - _A._ Cross-section of calamus rhizome (_Acorus calamus_, L.). 1, - Intercellular space; 2, Parenchyma cells; 3, Secretion cavity. - _B._ Cross-section of white pine bark (_Pinus strobus_, L.). 1, - Parenchyma; 2, Secretion cavity; 3, Secretion cells.] - -[Illustration: PLATE 63 - - _A._ Cross-section of a portion of canella alba bark (_Canella - alba_, Murr.). 1. Excretion cavity. - _B._ Cross-section of a portion of klip buchu leaf. - 1. Epidermal cells. - 2. Secretion cavity. - 3. Secretion cells.] - -[Illustration: PLATE 64 - - _A._ Cross-section of bitter orange peel (_Citrus aurantium_, - _amara_, L.). 1, Internal secretion cavity formed by the - dissolution of the walls of the central secreting cells; 2, - Secretion cells. _B._ Cross-section of white pine leaf (_Pinus - strobus_, L.). 1, Epidermal and hypodermal cells; 2, Parenchyma - cells with protruding inner walls; 3, Endodermis; 4, Secretion - cavity; 5, Secretion cells.] - -In calamus (Plate 62, Fig. A) the cavity is larger than the -surrounding cells; it is rounded in outline, and it contains -oleoresin. These cavities are in contact with the ordinary parenchyma -cells, from which they are easily distinguished by their larger size -and rounded form. - -The =unicellular oil cavity= of canella alba (Plate 63, Fig. A) is -rounded or oval in cross-section and is many times larger than the -surrounding cells. The wall, which is very thick, is of a yellowish -color. - -Secretion cavities vary greatly in form, according to the part of the -plant in which they are found. In flower petals and leaves they are -spherical; in barks they are usually elliptical; in umbelliferous -fruits they are elongated and tube-like. - -Mucilage cavities are not of common occurrence in medicinal plants. -They occur, however, in the stem and root bark of sassafras, the stem -bark of slippery elm, the root of althea, etc. - - - - - CHAPTER VIII - - STORAGE TISSUE - - -Most drug plants contain storage products because they are -collected at a period of the year when the plant is storing, or has -stored, reserve products. These products are stored in a number of -characteristic ways and in different types of tissue. - -The most important of the different types of storage tissue that -occurs in plants are the storage cells, the storage cavities, and the -storage walls. - - - STORAGE CELLS - -Several different types of cells function as storage tissue. These -cells, which are given in the order of their importance, are -parenchyma, crystal cells, medullary rays, stone cells, wood fibres, -bast fibres, and epidermal and hypodermal cells. - - - CORTICAL PARENCHYMA - -=Cortical parenchyma= of biennial rhizomes, bulbs, roots, and the -parenchyma of the endosperm of seeds store most of the reserve -economic food products of the higher plants. - -=Pith parenchyma= of sarsaparilla root (Plate 65, Fig. 4) and -the pith parenchyma of the rhizome of memspermun, like the pith -parenchyma of most plants, function as storage cells. - - - WOOD PARENCHYMA - -=Wood parenchyma=, particularly of the older wood, function as -storage tissue. The wood parenchyma of quassia, like the wood -parenchyma of most woods, contain stored products. In some cases the -wood parenchyma contain starch, in others crystals, and in others -coloring matter, etc. - -[Illustration: PLATE 65 - - 1. Stone cells with starch of Ceylon cinnamon (_Cinnamomum - ceylanicum_, Nees.). 2. Stone cells with solitary crystals of - calumba root (_Jateorhiza palmata_, [Lam.] Miers). 3. Parenchyma - cells, with starch of cascarilla bark (_Croton eluteria_, [L.] - Benn.). 4. Cortical parenchyma with starch of sarsaparilla root - (_Smilax officinalis_, Kunth). 5. Cortical parenchyma, with - starch of leptandra rhizome (_Leptandra virginica_, [L.] Nutt.). - 6. Crystal cells, with solitary crystals of quebracho bark - (Schlechtendal). 7. Bast fibre of blackberry root with starch - (_Rubus cuneifolius_, Pursh.).] - -[Illustration: PLATE 66 - - MUCILAGE AND RESIN - - 1. Cross-section of elm bark (_Ulmus fulva_, Michaux) showing two - cavities filled with partially swollen mucilage. - 2. Mucilage mass from sassafras stem bark (_Sassafras variifolium_, - L.). - 3. Mucilage mass from elm bark. - 4. Resin mass from white pine bark (_Pinus strobus_, L.).] - -In many plants, however, the parenchyma cells contain crystals. The -parenchyma cells of rhubarb contain rosette crystals, while the -parenchyma cells of the cortex of sarsaparilla and false unicorn root -contain bundles of raphides. In every case observed the raphides are -surrounded by mucilage. This is true of squills, sarsaparilla, false -unicorn, etc. When cells with raphides and mucilage are mounted in a -mixture of alcohol, glycerine, and water, the mucilage first swells -and finally disappears. - - - STORAGE CAVITIES - -Particular attention should be given to =storage cavities= whenever -they occur in plants, for the reason that they are usually filled -with storage products, and for the added reason that storage cavities -are not common to all plants. Storage cavities occur in roots, stems, -leaves, flowers, fruits, and seeds. - - - CRYSTAL CAVITIES - -Characteristic =crystal cavities= occur in many plants. Such a cavity -containing a bundle of raphides is shown in the cross-section of -skunk cabbage leaf (Plate 67). - - - SECRETION CAVITIES - -In white pine bark there are a great number of secretion cavities -which are partially or completely filled with oleoresin. In the -cross-sections of white pine bark the secretion cavities are very -conspicuous, and they vary greatly in size. This variation is due, -first, to the age of the cavity, the more recently formed cavities -being smaller; and secondly, to the nature of the section, which will -be longer in longitudinal section, which will be through the length -of the secretion cavity, and shorter on transverse section. Such a -section shows the width of the secretion cavity. - -Characteristic =mucilage cavities= occur in sassafras root, stem -bark, elm bark (Plate 66, Fig. 1), marshmallow root, etc. These -cavities form a conspicuous feature of the cross-section of these -plants. The presence or absence of mucilage cavities in a bark should -be carefully noted. - - - LATEX CAVITIES - -The =latex tube cavities= are characteristic in the plants in which -they occur. These cavities as explained under latex tubes are very -irregular in outline. - -[Illustration: PLATE 67 - - CROSS-SECTION OF SKUNK-CABBAGE LEAF (_Symplocarpus fœtidus_, - [L.] Nutt.) - - 1. Crystal cavity. - 2. Bundle of raphides.] - - - OIL CAVITY - -Canella alba contains an =oil cavity= resembling in form the mucilage -cavity of elm bark. - -=Secretion cavities= occur in most of the umbelliferous fruits. For -each fruit there is a more or less constant number of cavities. Anise -has twenty or more, fennel usually has six cavities, and parsley has -six cavities. - -In poison hemlock fruits there are no secretion cavities. In certain -cases, however, the number of secretion cavities can be made to vary. -This was proved by the author in the case of celery seed. He found -that cultivated celery seed, from which stalks are grown, contains -six oil cavities (Plate 122, Fig. 2), while wild celery seed (Plate -102, Fig. 1), grown for its medicinal value, always contains more -than six cavities. Most of the wild celery seeds contain twelve -cavities. - -Many leaves contain cavities for storing secreted products. Such -storage cavities occur in fragrant goldenrod, buchu, thyme, savary, -etc. - -The leaves in which such cavities occur are designated as -pellucid-punctate leaves. Such leaves will, when held between the eye -and the source of light, exhibit numerous rounded translucent spots, -or storage cavities. - - - GLANDULAR HAIRS - -The =glandular hair of peppermint= (Plate 60, Fig. 3) and other mints -consists of eight secretion cells, arranged around a central cavity -and an outer wall which is free from the secretion cells. This outer -wall becomes greatly distended when the secretion cells are active, -and the space between the secretion cells and the wall serves as the -storage place for the oil. When the mints are collected and dried, -the oil remains in the storage cavity for a long time. - - - STONE CELLS - -The =stone cells= of the different cinnamons (Plate 65, Fig. 1) store -starch grains; these grains often completely fill the stone cells. - -The yellow stone cells of calumba root (Plate 65, Fig. 2) usually -contain four prisms of calcium oxalate, which may be nearly uniform -or very unequal in size. - - - BAST FIBRES - -The =bast fibres= of the different rubus species (Plate 65, Fig. 7) -contain starch. The medullary rays of quassia (Plate 107, Fig. 2) -contain starch; while the medullary rays of canella alba contain -rosette crystals. In a cross-section of canella alba (Plate 81, Fig. -3) the crystals form parallel radiating lines which, upon closer -examination, are seen to be medullary rays, in each cell of which a -crystal usually occurs. - -The =epidermal and hypodermal cells of leaves= serve as water-storage -tissue. These cells usually appear empty in a section. - -The barks of many plants--_i.e._, quebracho, witch-hazel, -cascara, frangula, the leaves of senna and coca, and the root of -licorice--contain numerous crystals. These crystals occur in special -storage cells--=crystal cells= (Plate 65, Fig. 6)--which usually form -a completely enveloping layer around the bast fibres. These cells are -usually the smallest cells of the plant in which they occur, and with -but few exceptions each cell contains but a single crystal. - -The epidermal cells of senna leaves and the epidermal cells of -mustard are filled with mucilage; the walls even consist of mucilage. -Such cells are always diagnostic in powders. - - - STORAGE WALLS - -=Storage walls= (Plates 68 and 69) occur in colchicum seed, saw -palmetto seed, areca nut, nux vomica, and Saint Ignatius’s bean. In -each of these seeds the walls are strongly and characteristically -thickened and pitted. In no two plants are they alike, and in each -plant they are important diagnostic characters. - -Storage cell walls consist of reserve cellulose, a form of cellulose -which is rendered soluble by ferments, and utilized as food during -the growth of the seed. Reserve cellulose is hard, bony, and of a -waxy lustre when dry. Upon boiling in water the walls swell and -become soft. - -The structure of the reserve cellulose varies greatly in the -different seeds in which it occurs in the thickness of the walls and -in the number and character of the pores. - -[Illustration: PLATE 68 - - RESERVE CELLULOSE - - 1. Saw palmetto (_Serenoa serrulata_, [Michaux] Hook., f.). - 2. Areca nut (_Areca catechu_, L.). - 3. Colchicum seed (_Colchicum autumnale_, L.). - 3-_A_. Porous side wall. - 3-_B_. Cell cavity above the side wall.] - -[Illustration: PLATE 69 - - RESERVE CELLULOSE - - 1. Endosperm of nux vomica (_Strychnos nux vomica_, L.). - 2. Endosperm of St. Ignatia bean (_Strychnos ignatii_, Berg.).] - - - - - CHAPTER IX - - CELL CONTENTS - - -The cell contents of the plant are divided into two groups: first, -organic cell contents; and secondly, inorganic cell contents. - -The =organic= cell contents include plastids, starch grains, -mucilage, inulin, sugar, hesperidin, alkaloids, glucocides, tannin, -resin, and oils. - - - CHLOROPHYLL - -The =chloroplasts= of the higher plants are green, and they vary -somewhat in size, but they have a similar structure and form. - -Chloroplasts are mostly oval in longitudinal view and rounded in -cross-section view. Each chlorophyll grain has an extremely thin -outer wall, which encloses the protoplasmic substance, the green -granules, a green pigment (chlorophyll), and a yellow pigment -(xanthophyll). Frequently the wall includes starch, oil drops, and -protein crystals. - -Chloroplasts are arranged either in a regular peripheral manner along -the walls, or they are diffused throughout the protoplast. - -The palisade cells of most leaves are packed with chlorophyll grains. -In the mesophyll cells the chlorophyll grains are not so numerous, -and they are arranged peripherally around the innermost part of the -wall. - -Chloroplasts multiply by fission--that is, each chloroplast divides -into two equal halves, each of which develops into a normal -chloroplast. - -Chlorophyll occurs in the palisade, spongy parenchyma, and guard -cells of the leaf; in the collenchyma and parenchyma of the cortex -of the stems of herbs and of young woody stems, and, under certain -conditions, in rhizomes and roots exposed to light. Almost without -exception young seeds and fruits have chlorophyll. - -In powdered leaves, stems, etc., the chlorophyll grains occur in the -cells as greenish, more or less structureless masses. Yet cells with -chlorophyll are readily distinguished from cells with other cell -contents. In witch-hazel leaf the chlorophyll grains appear brownish -in color. Powdered leaves and herbs are readily distinguished from -bark, wood, root, and flower powders. - -Leaves and the stems of herbs are of a bright-green color. With the -exception of the guard cells, the chloroplasts occur one or more -layers below the epidermis; but, owing to the translucent nature of -the outer walls of these cells, the outer cells of leaves and stems -appear green. - -Wild cherry, sweet birch, and, in fact, most trees with smooth barks -have =chloroplasts= in several of the outer layers of the cortical -parenchyma. When the thin outer bark is removed from these plants, -the underlying layers are seen to be of a bright-green color. - - - LEUCOPLASTIDS - -=Leucoplastids=, or colorless plastids, occur in the underground -portions of the plant; they may, when these organs in which they -occur are exposed to light, change to chloroplastids. - -Leucoplasts are the builders of starch grains. They take the chemical -substance starch and build or mould it into starch grains, storage -starch, or reserve starch. - -Other characteristic chromoplasts found in plants are yellow and -red. Yellow chromoplasts occur in carrot root and nasturtium flower -petals. Red plastids occur in the ripe fruit of capsicum. - - - STARCH GRAINS - -The chemical substance starch (C₆H₁₀O₅) is formed in chloroplasts. -The starch thus formed is removed from the chloroplasts to other -parts of the plant because it is the function of the chloroplasts to -manufacture and not to store starch. - -The starch formed by the chloroplasts is acted upon by a ferment -which adds one molecule of water to C₆H₁₀O₅, thus forming sugar -C₆H₁₂O₆. This sugar is readily soluble in the cell sap, and is -conducted to all parts of the plant. The sugar not utilized in cell -metabolism is stored away in the form of reserve starch or starch -grains by colorless plastids or amyloplasts. - -The amyloplasts change the sugar into starch by extracting a molecule -of water. This structureless material (starch) is then formed by the -amyloplast into starch grains having a definite and characteristic -form and structure. - -Starch grams vary greatly in different species of plants, owing -probably to the variation of the chemical composition, density, etc., -of the protoplast, and to the environmental conditions under which -the plant is growing. - - - OCCURRENCE - -Starch grains are simple, compound, or aggregate. =Simple starch= -grains may occur as isolated grains (Plates 70, 71, and 72), or they -may be associated as in cardamon seed, white pepper, cubeb, and -grains of paradise, where the simple grains stick together in masses, -having the outline of the cells in which they occur. These masses are -known as aggregate starch. - -=Aggregate starch= (Plate 76) varies greatly in size, form, and in -the nature of the starch grains forming the aggregations. - -=Compound starch grains= may be composed of two or more parts, and -they are designated as 2, 3, 4, 5, etc., compound (Plate 75). - -The parts of a compound grain may be of equal size (Plate 75, Fig. -4), or they may be of unequal size (Plate 75, Fig. 2). - -In most powders large numbers of the parts of the compound grains -become separated. The part in contact with other grains shows plane -surfaces, while the external part of the grain has a curved surface. -There will be one plane and one curved surface if the grain is a half -of a two-compound grain; two plane and one curved surface if the -grain is a part of a three-compound grain, etc. - -The simple starch grains forming the aggregations become separated -during the milling process and occur singly, so that in the drugs -cited above the starch grains are solitary and aggregate. - -Many plants contain both simple and compound starch grains (Plate 74, -Fig. 3). - -In some forms--_e.g._, belladonna root (Plate 75, Fig. 2) the -compound grains are more numerous; while in sanguinaria the simple -grains are more numerous, etc. - - - OUTLINE - -The =outline= of starch grains is made up of (1) rounded, (2) angled, -and (3) rounded and angled surfaces. - -Starch grains with rounded surfaces may be either spherical, as in -Plate 74, Fig. 3, or oblong or elongated, as in Plate 71, Fig. 1. - -Other starches with rounded surfaces are shown on Plates 72 and 73. - -Angled outlined grains are common to cardamon seed, white pepper, -cubebs, grains of paradise (Plate 76, Fig. 4), and to corn (Plate 70, -Fig. 3). - -The outlines of all compound grains are made up partly of plane and -partly of curved surfaces. - - - SIZE - -The =size= (greatest diameter) of starch varies greatly even in the -same species, but for each plant there is a normal variation. - -In spherical starch grains the size of the individual grains is -invariable, but in elongated starch grains and in parts of compound -grains the size will vary according to the part of the grain -measured. In zedoary starch (Plate 71, Fig. 4), for instance, the -size will vary according to whether the end, side, or surface of the -starch grain is in focus. - -The parts of compound grains often vary greatly in size. Such a -variation is shown in Plate 75, Fig. 2. - - - HILUM - -The =hilum= is the starting-point of the starch grain or the first -part of the grain laid down by the amyloplast. The hilum will be -central if formed in the middle of the amyloplast, and excentral if -formed near the surface of the amyloplast. It has been shown that the -developing starch grain with eccentric hilum usually extends the wall -of the amyloplast if it does not actually break through the wall. -Starch grains with excentral hilums are therefore longer than broad. - -[Illustration: PLATE 70 - - STARCH - - 1. Calabar bean (_Physostigma venenosum_, Balfour). - 2. Marshmallow root (_Althæa officinalis_, L.). - 3. Field corn (_Zea mays_, L.).] - -[Illustration: PLATE 71 - - STARCH - - 1. Galanga root (_Alpinia officinarum_, Hance). 2. Kola nut (_Cola - vera_, [K.] Schum.). 3. Geranium rhizome (_Geranium maculatum_ L.). - 4. Zedoary root (_Curcuma zedoaria_, Rosc.). 4-_A_. Surface view of - starch grain. 4-_B_. Side view of starch grain. 4-_C_. End view of - starch grain.] - -In central hilum starch grains the grain is laid down around the -hilum in the form of concentric layers. These layers are of variable -density. The dense layers are formed when plenty of sugar is -available, and the less dense layers are formed when little sugar -is available. The unequal density of the different layers gives the -striated appearance characteristic of so many starch grains. - -In eccentric hilum starch grains the starch will be deposited in -layers which are outside of and successively farther from the hilum. - -The term _hilum_ has come to have a broader meaning than formerly. -Hilum includes at the present time not only the starting-point of the -starch grain, but the fissures which form in the grain upon drying. -In all cases these fissures originate in the starting-point, hilum, -and in some cases extend for some distance from it. The hilum, when -excentral, may occur in the broad end of the grain, galanga, and -geranium (Plate 71, Figs, 1 and 3), or in the narrow end of the -grain, zedoary (Plate 71, Fig. 4). - - - NATURE OF THE HILUM - -The hilum, whether central or excentral, may be rounded (Plate 75, -Fig. 1); or simple cleft, which may be straight (Plate 71, Fig. 1); -or curved cleft (Plate 71, Fig. 2); or the hilum may be a multiple -cleft (Plate 74, Fig. 3). - -In studying starches use cold water as the mounting medium, because -in cold water the form and structure are best shown, and because -there is no chemical action on the starch. On the other hand, the -form and structure will vary considerably if the starch is mounted -in hot water or in solutions of alkalies or acids. The hilum appears -colorless when in sharp focus, and black when out of focus. - -Starch grains, when boiled with water, swell up and finally -disintegrate to form starch paste. - -Starch paste turns blue upon the addition of a few drops of weak -Lugol solution. Upon heating, this blue solution is decolorized, but -the color reappears upon cooling. If a strong solution of Lugol is -used in testing, the color will be bluish black. - -[Illustration: PLATE 72 - - STARCH - - 1. Orris root (_Iris florentinia_ L.). - 2. Stillingia root (_Stillingia sylvatica_, L.). - 3. Calumba root (_Jateorhiza palmata_, [Lam.] Miers.).] - -[Illustration: PLATE 73 - - STARCH - - 1. Male fern (_Dryopteris marginalis_, [L.] A. Gray). - 2. African ginger (_Zingiber officinalis_, Rosc.). - 3. Yellow dock (_Rumex crispus_, L.). - 4. Pleurisy root (_Asclepias tuberosa_, L.).] - -[Illustration: PLATE 74 - - STARCH - - 1. Kava-kava (_Piper methysticum_, Forst., f.). - 2. Pokeroot (_Phytolacca americana_, L.). - 3. Rhubarb (_Rheum officinale_, Baill.).] - -[Illustration: PLATE 75 - - STARCH GRAINS - - 1. Bryonia (_Bryonia alba_, L.). - 2. Belladonna root (_Atropa belladonna_, L.). - 3. Valerian root (_Valeriana officinalis_, L.). - 4. Colchicum root (_Colchicum autumnale_, L.).] - -[Illustration: PLATE 76 - - STARCH MASSES - - 1. Aggregate starch of cardamon seed (_Elettaria cardamomum_, - Maton). - 2. Aggregate starch of white pepper (_Piper nigrum_, L.). - 3. Aggregate starch of cubebs (_Piper cubeba_, L., f.). - 4. Aggregate starch of grains of paradise (_Amomum melegueta_, - Rosc.).] - - - INULIN - -=Inulin= is the reserve carbohydrate material found in the plants of -the composite family. - -The medicinal plants containing inulin are dandelion, chicory, -elecampane, pyrethrum, and burdock. Plate 77, Figs, 1 and 2 show -masses of inulin in dandelion and pyrethrum. - -In these plants the inulin occurs in the form of irregular, -structureless, grayish-white masses (Plate 77). In powdered drugs -inulin occurs either in the parenchyma cell or as irregular isolated -fragments of variable size and form. Inulin is structureless and the -inulin from one plant cannot be distinguished microscopically from -the inulin of another plant. For this reason inulin has little or no -diagnostic value. The presence or absence of inulin should always be -noted, however, in examining powdered drugs, because only a few drugs -contain inulin. - -When cold water is added to a powder containing inulin it dissolves. -Solution will take place more quickly, however, in hot water. -Inulin occurs in the living plant in the form of cell sap. If fresh -sections of the plant are placed in alcohol or glycerine, the inulin -precipitates in the form of crystals. - - - MUCILAGE - -=Mucilage= is of common occurrence in medicinal plants. -Characteristic mucilage cavities filled with mucilage occur in -sassafras stem (Plate 66, Fig. 2), in elm bark (Plate 66, Fig. 1), in -althea root, in the outer layer of mustard seed, and in the stem of -cactus grandiflorus. In addition, mucilage is found associated with -raphides in the crystal cells of sarsaparilla, squill, false unicorn, -and polygonatum. - -When drugs containing mucilage are added to alcohol, glycerine, and -water mixture, the mucilage swells slightly and becomes distinctly -striated, but it will not dissolve for a long time. Refer to Plate -79, Fig. 6. - -Mucilage, when associated with raphides, swells and rapidly dissolves -when added to alcohol, glycerine, and water mixture. The mucilage is, -therefore, different from the mucilage found in mucilage cavities, -because it is more readily soluble. - -[Illustration: PLATE 77 - - INULIN (_Inula helenium_, L.) - - 1. Inulin in the parenchyma cells of dandelion root. - 2. Inulin from Roman pyrethrum root (_Anacyclus pyrethrum_, [L.] D. - C.). ] - -In coarse-powdered bark and other mucilage containing drugs the -mucilage masses are mostly spherical or oval in outline (Plate 66, -Figs. 2 and 3) the form being similar to the cavity in which the mass -occurs. - -Acacia, tragacanth, and India gum consist of the dried mucilaginous -excretions. - - - HESPERIDIN - -=Hesperidin= occurs in the epidermal cells of short and long buchu. -It is particularly characteristic in the epidermal cells of the dried -leaves of short buchu. In these leaves the hesperidin occurs in -masses which resemble rosette crystals (Plate 54, Fig. 1). - -Hesperidin is insoluble in glycerine, alcohol, and water, but it -dissolves in alkali hydroxides, forming a yellowish solution. - - - VOLATILE OILS - -=Volatile oils= occur in cinnamon stem bark, sassafras root bark, -flowers of cloves, and in the fruits of allspice, anise, fennel, -caraway, coriander, and cumin. - -In none of these cases is the volatile oil diagnostic, but its -presence must always be determined. - -When a powdered drug containing a volatile oil is placed in alcohol, -glycerine, and water mixture the volatile oil contained in the -tissues will accumulate at the broken end of the cells in the form of -rounded globules, while the volatile oil adhering to the surface of -the fragments will dissolve in the mixture and float in the solution -near the under side of the cover glass. Volatile oil is of little -importance in histological work. - - - TANNIN - -=Tannin= masses are usually red or reddish brown. Tannin occurs in -cork cells, medullary rays of white pine bark (Plate 48, Fig. B), -stone cells, and in special tannin sacs. - -The stone cells of hemlock and tamarac bark and the medullary rays of -white pine and hemlock bark contain tannin. - -Tannin associated with prisms occurs in tannin sacs in white pine and -tamarac bark. These sacs are frequently several millimeters in length -and contain a great number of crystals surrounded by tannin. - -Deposits of tannin are colored bluish black with a solution of ferric -chloride. - - - ALEURONE GRAINS - -=Aleurone grains= are small granules of variable structure, size, -and form, and they are composed of reserve proteins. They occur in -celery, fennel, coriander, and anise, fruits, in sesame, sunflower, -curcas, castor oil, croton oil, bitter almond, and other oil seeds. - -In many of the seeds the aleurone grains completely fill the cells of -the endosperm, embryo, and perisperm. In wheat, rye, barley, oats, -and corn the aleurone grains occur only in the outer layer or layers -of the endosperm, the remaining layers in these cases being filled -with starch. - -In powdered drugs the aleurone grains occur in parenchyma cells or -free in the field. - - - STRUCTURE OF ALEURONE GRAINS - -Aleurone grains are very variable in structure. The simplest grains -consist of an undifferentiated mass of proteid substance surrounded -by a thin outer membrane. In other grains the proteid substance -encloses one or more rounded denser proteid bodies known as globoids. -In other grains a crystalloid--crystal-like proteid substance--is -present in addition to the globoid. In some grains are crystals -of calcium oxalate, which may occur as prisms or as rosettes. All -the different parts, however, do not occur in any one grain. In -castor-oil seed (Plate 77_a_, Fig. 8) are shown the membrane (_A_), -the ground mass (_B_), the crystalloid (_C_), and the globoid (_D_). - - - FORM OF ALEURONE GRAINS - -Much attention has been given to the study of the special parts -of the aleurone grains, but one of the most important diagnostic -characters has been overlooked, namely, that of comparative form. For -the purposes of comparing the forms of different grains, they should -be mounted in a medium in which the grain and its various parts are -insoluble. Oil of cedar is such a medium. The variation in form and -size of the aleurone grains when mounted in oil of cedar is shown in -Plate 77_a_. - - - DESCRIPTION OF ALEURONE GRAINS - -The aleurone grains of curcas (Plate 77_a_, Fig. 1) vary in form -from circular to lens-shaped, and each grain contains one or more -globoids. The globoids are larger when they occur singly. In -sunflower seed (Plate 77_a_, Fig. 2) the grains vary from reniform to -oval, and one or more globoids are present; many occur in the center -of the grain. - -The aleurone grains of flaxseed (Plate 77_a_, Fig. 3) resemble in -form those of sunflower seed, but the grains are uniformly larger and -some of the grains contain as many as five globoids. - -In bitter almond (Plate 77_a_, Fig. 4) the aleurone grains are mostly -circular, but a few are nearly lens-shaped. A few of the large, -rounded grains contain as many as nine globoids; in such cases one -of the globoids is likely to be larger than the others. The aleurone -grains of croton-oil seed (Plate 77_a_, Fig. 5) are circular in -outline, variable in form, and each grain contains from one to seven -globoids. - -In sesame seed (Plate 77_a_, Fig. 6) the typical grain is angled in -outline and the large globoid occurs in the narrow or constricted end. - -The aleurone grains of castor-oil seed (Plate 77_a_, Fig. 7) resemble -those of sesame seed, but they are much larger, and many of the -grains contain three large globoids. When these grains are mounted in -sodium-phosphate solution, the crystalloid becomes visible. - - - TESTS FOR ALEURONE GRAINS - -Aleurone grains are colored yellow with nitric acid and red with -Millon’s reagent. - -The proteid substance of the mass of the grain, of the globoid, and -of the crystalloid, reacts differently with different reagents and -dyes. - -The ground substance and the crystalloids are soluble in dilute -alkali, while the globoids are insoluble in dilute alkali. - -The ground substance and crystalloids are soluble in sodium -phosphate, while the globoids are insoluble in sodium phosphate. - -Calcium oxalate is insoluble in alkali and acetic acid, but it -dissolves in hydrochloric acid. - -[Illustration: PLATE 77_a_ - - ALEURONE GRAINS - - 1. Curcas (_Jatropha curcas_, L.). - 2. Sunflower seed (_Helianthus annuus_, L.). - 3. Flaxseed (_Linum usitatissimum_, L.). - 4. Bitter almond (_Prunus amygdalus_, _amara_, D.C.). - 5. Croton-oil seed (_Croton tiglium_, L.). - 6. Sesame seed (_Sesamum indicum_, L.). - 7 and 8. Castor-oil seed (_Ricinus communis_, L.).] - - - CRYSTALS - -Calcium oxalate crystals form one of the most important inorganic -cell contents found in plants, because of the permanency of the -crystals, and because the forms common to a given species are -invariable. By means of calcium oxalate crystals it is possible to -distinguish between different species. In butternut root bark, for -instance, only rosette crystals are found, while in black walnut -root bark--a common substitute for butternut bark--both prisms and -rosettes occur. This is only one of the many examples which could be -cited. - -These crystals, for purposes of study, will be grouped into four -principal classes, depending upon form and not upon crystal system. -These classes are micro-crystals, raphides, rosettes, and solitary -crystals. - - - MICRO-CRYSTALS - -=Micro-crystals= are the smallest of all the crystals. Under the -high power of the microscope they appear as a V, a Y, an X, and as -a T. They are, therefore, three- or four-angled (Plate 78). The -thicker portions of these crystals are the parts usually seen, but -when a close observation of the crystals is made the thin portions -of the crystal connecting the thicker parts may also be observed. -Micro-crystals should be studied with the diaphragm of the microscope -nearly closed and with the high-power objective in position. While -observing the micro-crystals, raise and lower the objective by the -fine adjustment in order to bring out the structure of the crystal -more clearly. Micro-crystals occur in parenchyma cells of belladonna, -scopola, stramonium, and bittersweet leaves; in belladonna, in -horse-nettle root, in scopola rhizome, in bittersweet stems, and in -yellow and red cinchona bark, etc. - -The crystals in each of the above parts of the plant are similar in -form, the only observed variation being that of size. Their presence -or absence should always be noted when studying powders. - - - RAPHIDES - -=Raphides=, which are usually seen in longitudinal view, resemble -double-pointed needles. They are circular in cross-section, and the -largest diameter is at the centre, from which they taper gradually -toward either end to a sharp point. - -[Illustration: PLATE 78 - - MICRO-CRYSTALS - - 1. Horse-nettle root (_Solanum carolinense_, L.). - 2. Scopola rhizome (_Scopolia carniolica_, Jacq.). - 3. Belladonna root (_Atropa belladonna_, L.). - 4. Bittersweet stem (_Solanum dulcamara_, L.). - 5. Scopola leaf (_Scopola carniolica_, Jacq.). - 6. Tobacco leaf (_Nicotiana tabacum_, L.). - 7. Belladonna leaf (_Atropa belladonna_, L.).] - -Raphides occur in bundles, as in false unicorn root (Plate 79, Figs. -6, A, B, and C), rarely as solitary crystals. - -In ipecac root the crystals are usually solitary. In sarsaparilla -root, squill, etc., the raphides occur both in clusters, part of -bundle, or in bundles, and as solitary crystals. - -In most drugs the crystals are entire; but in squills, where the -raphides are very large, they are broken. In phytolacca (Plate 79, -Fig. 1) and in hydrangea the raphides are usually broken, owing to -the fact that these drugs contain large quantities of fibres which -break them up into fragments when the drug is milled. - -There is the greatest possible variation in the size of raphides in -the same and in different drugs, but the larger forms are constant in -the same species. - -Raphides are deposited in parenchyma cells and in special raphides -sacs. These crystals are always surrounded with mucilage. - - - ROSETTE CRYSTALS - -=Rosette crystals= are compound crystals composed of an aggregation -of small crystals arranged in a radiating manner around a central -core. This core appears nearly black, and the whole mass is nearly -spherical. The free ends of the crystals are sharp-pointed or blunt. - -Characteristic rosette crystals occur in frangula bark, spikenard -root, wahoo stem, root bark, rhubarb, etc. (Plate 80, Figs. 1, 2, 3, -4, 5, and 6). - -These crystals are very variable in size. This variation is -illustrated by the crystals of Plate 80. - -Usually there is a variation in size of the crystals occurring in -a given plant, but for each plant there is a more or less uniform -variation. For instance, the largest rosette crystal occurring in -wahoo root bark (Plate 80, Fig. 5) is smaller than the largest -crystal occurring in rhubarb (Plate 80, Fig. 6), etc. - -[Illustration: PLATE 79 - - RAPHIDES - - 1. Phytolacca root (_Phytolacca americana_, L.). 2. Squills - (_Urginea maritima_ [L.] Baker). 3. Hydrangea root (_Hydrangea - arborescens_, L.). 4. Convallaria (_Convallaria majalis_, L.). - 5. Carthagean ipecac (_Cephælis acuminata_ Karst.) 6. Bundle of - raphides from false unicorn root. - - _A._ Bundle surrounded with mucilage. _B._ Mucilage expanded and - partially dissolved. _C._ Bundle free of mucilage.] - -[Illustration: PLATE 80 - - ROSETTE CRYSTALS - - 1. Frangula bark (_Rhamnus frangula_, L.). - 2. White oak bark (_Quercus alba_, L.). - 3. Spikenard root (_Aralia racemosa_, L.). - 4. Wahoo stem bark (_Euonymus atropurpureus_, Jacq.). - 5. Wahoo root bark (_Euonymus atropurpureus_, Jacq.). - 6. Rhubarb (_Rheum officinale_, Baill.).] - -The prisms forming the rosette crystals, like all prisms, decompose -white light, with the result that rosette crystals frequently appear -variously colored. Rhubarb crystals, for instance, are blue or -violet. Most of the smaller rosette crystals, however, appear grayish -white with a darker-colored centre. - -Rosette crystals occur in parenchyma cells (Plate 81, Fig. 4) and in -medullary rays (Plate 81, Fig. 3). - - - SOLITARY CRYSTALS - -=Solitary crystals= are the most variable of all the forms of calcium -oxalate. They usually occur in crystal cells associated with bast -fibres and stone cells, less frequently in stone cells (Plate 33, -Fig. 2). There are many different and characteristic forms of prisms. -The more common are: - - 1. Rectangular: - A. Parallelepipeds. - B. Cubes. - 2. Polyhedrons: - A. Irregular polyhedrons. - I. Flat bases. - (_a_) Non-notched. - (_b_) Notched. - II. Tapering bases. - B. Octohedrons. - -The crystals occurring in Batavia cinnamon and henbane leaves are -parallelopipeds (Plate 82, Figs. 1 and 2). - -The crystals occurring in cactus grandiflorus, hemlock bark, krameria -root, and soap bark are irregular polyhedrons (Plate 83). They -are longer than broad, and the ends are tapering. The crystal of -cactus grandiflorus has the narrowest diameter of these four, while -the crystals of soap bark have the widest diameter. In coca leaf, -xanthoxylum bark, elm bark, Spanish licorice, and in white oak (Plate -84), and in cocillina bark (Plate 82, Fig. 4) the crystals are all -irregular polyhedrons with flat bases. They are mostly longer than -broad and they are all widest in the centre; in each a few crystals -are notched, but most of the crystals are not notched. - -The crystals in quassia wood, uva-ursi leaf, and most of those of -quebracho and wild cherry bark (Plate 86, Figs. 1, 2, 3, and 4) are -irregular polyhedrons with flat ends. They are longer than broad, -widest at the centre, and non-notched. - -[Illustration: PLATE 81 - - INCLOSED ROSETTE CRYSTALS - - 1. Hops (_Humulus lupulus_, L.). - 2. Bracts of cannabis indica (_Cannabis sativa_, variety _Indica_, - Lamarck). - 3. Medullary rays of canella alba. - 4. Parenchyma cells of mandrake (_Podophyllum peltatum_, L.).] - -[Illustration: PLATE 82 - - SOLITARY CRYSTAL - - 1. Batavia cinnamon (_Cinnamomum burmanni_, Nees). - 2. Henbane leaves (_Hyoscyamus niger_, L.). - 3. Morea nutgalls. - 4. Cocillana bark (_Guarea rusbyi_ [Britton], Rusby).] - -[Illustration: PLATE 83 - - SOLITARY CRYSTALS - - 1. Cactus grandiflorus (_Cereus grandiflorus_ [L.], Britton and - Rose). - 2. Hemlock bark (_Tsuga canadensis_ [L.], Carr.). - 3. Krameria root (_Krameria triandra_, Ruiz and Pav.). - 4. Soapbark (_Quillaja saponaria_, Molina).] - -[Illustration: PLATE 84 - - SOLITARY CRYSTALS - - 1. Coca leaf (_Erythroxylon coca_, Lamarck). - 2. Xanthoxylum bark (_Zanthoxylum americanum_, Miller). - 3. Elm bark (_Ulmus fulva_, Michaux). - 4. Spanish licorice root (_Glycyrrhiza glabra_, L.). - 5. White oak bark (_Quercus alba_, L.).] - -Cubes occur in senna, cascara sagrada, frangula, white pine, tamarac -(Plate 85), quassia, uva-ursi, quebracho, and in wild cherry (Plate -86). - -The crystals of morea nutgalls (Plate 82, Fig. 3) are octahedrons, -and they resemble the crystals of calcium oxalate found in urinary -sediments. - -While studying the prisms, focus first on the upper surface and then -down to the under surface in order to observe the forms accurately. - -There are several plants in which more than one form of crystal -occur. Rosette crystals and prisms are associated, for instance, in -cascara sagrada, frangula, condurango, dogwood, and pleurisy root -(Plate 87, Figs. 1, 2, 3, 4, and 5). - -An important factor to be kept in mind in studying crystals is the -number--whether abundant, as in rhubarb, or sparingly present, as in -mandrake, etc. Variation in the number of crystals is not uncommon, -even in different parts of the same plants. In wahoo stem bark, for -instance, there are several times as many rosette crystals as there -are in the root bark. - -Crystals of calcium oxalate are freely soluble in dilute hydrochloric -acid without effervescence; but they are insoluble in acetic acid and -in sodium and potassium hydroxide solutions. With sulphuric acid they -form crystals of calcium sulphate. - - - CYSTOLITHS - -=Cystoliths= consist of calcium carbonate deposited over and around a -framework of cellulose. - - - FORMS OF CYSTOLITHS - -The =forms of cystoliths= differ greatly in the different plants in -which they occur. - -In the rubber-plant leaf, the cystolith resembles a bunch of grapes -and is stalked; in ruellia root (Plate 87, Fig. 1) the cystoliths -vary from nearly circular to narrowly cylindrical, and no stalk is -present; also the cystolith nearly fills the cell in which it occurs. -In the hair of cannabis indica (Plate 88, Fig. 3), the cystolith -varies in form according to the size and shape of the hair, but in -all the hairs the cystolith appears to be attached to the upper -curved part of the inner wall of the hair. - -[Illustration: PLATE 85 - - SOLITARY CRYSTALS - - 1. India senna (_Cassia angustifolia_, Vahl.). - 2. Cascara sagrada bark (_Rhamnus purshiana_, D. C.). - 3. Frangula bark (_Rhamnus frangula_, L.). - 4. White pine bark (_Pinus strobus_, L.). - 5. Tamarac bark (_Larix laricina_ [Du Roi], Koch).] - -[Illustration: PLATE 86 - - SOLITARY CRYSTALS - - 1. Quassia (_Picræna excelsa_ [Swartz.], Lindl.). - 2. Uva-ursi leaf (_Arctostaphylos uva-ursi_ [L.], Spring.). - 3. Quebracho bark (_Aspidosperma quebracho-blanco_, Schlechtendal). - 4. Wild-cherry bark (_Prunus serotina_, Ehrh.).] - -[Illustration: PLATE 87 - - ROSETTE CRYSTALS AND SOLITARY CRYSTALS OCCURRING IN - - 1. Cascara sagrada bark (_Rhamnus purshiana_, D.C.). - 2. Frangula bark (_Rhamnus frangula_, L.). - 3. Cundurango bark (_Marsdenia cundurango_, [Triana] Nichols). - 4. Dogwood root bark (_Cornus florida_, L.). - 5. Pleurisy root (_Asclepias tuberosa_, L.).] - -[Illustration: PLATE 88 - - CYSTOLITHS - - 1. Ruellia root (_Ruellia ciliosa_, Pursh.). - 2. Pellionia leaf. - 3. Cannabis indica (_Cannabis sativa_, variety _Indica_, Lam.).] - -Cystoliths occur, then, in special cavities, in parenchyma -cells (rubber-plant leaf, fig, pellionea, and mulberry), and in -non-glandular hairs (cannabis indica). - -In powdered ruellia root the cystoliths occur in or are separated -from the parenchyma cells. - - - TESTS FOR CYSTOLITHS - -When dilute hydrochloric acid or acetic acid is added to cystoliths a -brisk effervescence takes place with the evolution of carbon dioxide -gas. - - - - - Part III - - HISTOLOGY OF ROOTS, RHIZOMES, STEMS, - BARKS, WOODS, FLOWERS, FRUITS, - AND SEEDS - - -In Part II the different types of cells and cell contents found in -plants have been studied. In Part III it will be shown how these -different cells are associated and the nature of the cell contents -in the different parts of the plant. These parts are the root, the -rhizome, the stem of herbs, bark and wood of woody stems, the leaf, -the flower, the fruit, and the seed. - - - - - CHAPTER I - - ROOTS AND RHIZOMES - - -Some fifty-five roots, rhizomes, and rhizomes and roots are official -in the pharmacopœia and national formulary. About 5 of these are -obtained from monocotyledonous plants, and 50 from dicotyledonous -plants. - -In studying the structure of roots and rhizomes, then, it must first -be determined whether the root in question is monocotyledonous or -dicotyledonous. This fact is ascertained by determining the type of -the fibro-vascular bundle. The bundle is of the open collateral type -in all rhizomes and roots obtained from monocotyledonous plants, but -it is closed, radial, or concentric in the monocotyledonous type. - -In both of these groups the cellular plan of structure is similar, -the chief variation being the absence of one or more types of cells, -the variation in the amount, in arrangement, in the anatomical -structure, in the color, and in the cell contents of the individual -cells. These facts will be impressed on the mind while studying the -rhizomes and the roots. - - - CROSS-SECTION PINK ROOT - -The cross-section of pink root (Plate 89) has the following structure: - -=Epidermis.= The epidermal cells are small, nearly as long as broad, -and the outer wall is thicker and darker in color than the side and -inner walls. The cells usually contain air. - -=Cortex.= The cortical parenchyma cells are very large and somewhat -rounded in outline, and the walls are white. There are about twelve -rows of these cells, and each cell contains numerous small, rounded -starch grains. - -=Endodermis.= The endodermal cells are tangentially elongated, and -the walls are very thin and white. There are two or three layers of -endodermal cells; the cells’ outer layers are larger than the cells -of the inner layers. - -[Illustration: PLATE 89 - - CROSS-SECTION OF ROOT OF SPIGELIA MARYLANDICA, L. - - 1. Epidermis. 2. Cortical parenchyma. 2´. Intercellular space. 3. - Endodermis. 4. Pericycle. 5. Cambium. 6. Xylem. 7. Pith.] - -=Pericycle.= The cells forming the pericycle are sieve cells and -phloem parenchyma. The =sieve cells= are small, angled cells with -extremely thin, white walls. - -The =phloem parenchyma= resemble the sieve cells, except that they -are larger. - -=Cambium.= The cambium cells are rectangular in shape; the walls are -thin and white. - -=Xylem.= The xylem is composed of tracheids, wood parenchyma, and -wood fibres. - -=Tracheids.= The tracheids are the largest diameter cells of the -centre of the root. The walls are thick and the cells are slightly -angled in outline. - -=Wood Parenchyma.= The wood parenchyma cells surrounding the -tracheids are five to seven, angled, and the walls are not so thick -as the walls of the tracheids. - -=Medullary Rays.= The medullary ray cells resemble the structure of -the wood parenchyma cells, but they are radially elongated. - -=Pith Parenchyma.= The cells forming the pith parenchyma are larger -than the cells of wood parenchyma, but their structure is similar. - - - CROSS-SECTION RUELLIA ROOT - -The cross-section of ruellia root (Plate 90) shows the following -structure. It should be carefully noted how the structure differs -from that of pink root: - -=Epidermis.= The epidermal cells are angled and variable in size; -many of the epidermal cells are modified as root hairs. - -=Hypodermis.= The cells of the hypodermis are one layer in thickness -and their structure is similar to the epidermal cells. - -=Cortex.= The cortex contains parenchyma and stone cells. The outer -layers of the cortical parenchyma cells are round in outline, and -they contain dark-brown cell contents, while the cortical parenchyma -cells bordering on the endodermis are small and they are free of -dark-brown contents. - -Many of the inner parenchyma cells contain amorphous deposits of -calcium carbonate. - -[Illustration: PLATE 90 - - RUELLIA ROOT (_Ruellia ciliosa_, Pursh.). - - 1. Epidermis with root hair. 2. Parenchyma cells with dark - contents. 3. Sclerid. 4. Parenchyma without dark cell contents. 5. - Endodermis. 6. Bast fibers and phloem. 7. Cambium. 8. Xylem. 10. - Pith.] - -The =stone cells= are porous and striated, and the walls are thick -and white. - -=Endodermis.= The endodermal cells are tangentially elongated, and -the walls are thin and white. - -=Pericycle.= The cells forming the pericycle are the sieve cells, -bast fibres, and phloem parenchyma. - -The =sieve cells= are small, angled cells with thin, white walls. - -The =phloem parenchyma= cells resemble the sieve cells, but they are -larger. - -The =bast fibres= occur singly or in groups of two or three. They -are rounded in outline, and the walls are white, non-porous, and -non-striated. - -=Xylem.= The xylem is composed of vessels, wood parenchyma, and wood -fibres. - -=Vessels.= The vessels are rounded in outline and few in number. - -=Wood Parenchyma.= The wood parenchyma cells are variable in size and -shape, but all the cells are angled in outline. - -=Medullary Rays.= The medullary ray cells are not clearly -distinguishable. - -=Pith Parenchyma.= The pith parenchyma cells of the centre of the -root resemble the cortical parenchyma cells. - -That the structure of rhizomes is similar to the structure of roots -is shown by the drawings of spigelia rhizome (Plate 91), and by -ruellia rhizome (Plate 92). - - - CROSS-SECTION SPIGELIA RHIZOME - -The cross-section of spigelia rhizome (Plate 91) is as follows: - -=Epidermis.= The epidermal cells are nearly angled and free of cell -contents. - -=Cortex.= The cortical parenchyma cells are usually slightly -tangentially elongated. The cells of the outer layers are larger than -the cells of the inner layers. - -=Phloem.= The phloem contains sieve cells and phloem parenchyma. The -sieve cells are small, angled cells with thin, white walls. - -The phloem parenchyma cells resemble the sieve cells, but they are -larger. - -[Illustration: PLATE 91 - - CROSS-SECTION OF RHIZOME OF SPIGELIA MARYLANDICA, L. - - 1. Epidermis. 2. Cortical parenchyma. 3. Phloem. 4. Cambium. 5. - Xylem. 6. Internal phloem. 7. Pith with starch.] - -[Illustration: PLATE 92 - - CROSS-SECTION OF RHIZOME OF RUELLIA CILIOSA, Pursh. - - 1. Epidermis. 2. Cystolith. 3. Stone cell. 4. Cortical parenchyma. - 5. Bast fibres. 6. Pericycle. 7. Xylem. 8. Pith.] - -=Cambium.= The cambium cells are rectangular, and they are usually -not clearly seen because the walls are partially collapsed. - -=Xylem.= The xylem is composed of vessels, wood parenchyma, medullary -rays, and pith parenchyma. - -=Vessels.= The vessels are slightly angled in outline and few in -number. - -=Wood Parenchyma.= The wood parenchyma cells are small and angled. - -=Medullary Rays.= The medullary ray cells are tangentially elongated, -but in structure resemble the wood parenchyma cells. - -=Pith Parenchyma.= The pith parenchyma cells are rounded in outline -and contain small, simple, rounded starch grains. - - - CROSS-SECTION RUELLIA RHIZOME - -The cross-section of ruellia rhizome (Plate 92) differs from the -structure of spigelia rhizome. It is as follows: - -=Epidermis.= The epidermal cells vary in shape from nearly square to -oblong, and they are filled with dark-brown cell contents. - -=Cortex.= The cortex contains parenchyma and stone cells. - -The outer layer of the cortical parenchyma cells are variable in size -and many of the cells contain deposits of calcium carbonate and dark -cell contents; the inner parenchyma cells are larger and they are -free of the dark-brown cell contents, but many of the cells contain -deposits of calcium carbonate. - -Stone cells with thick, white, porous, and striated walls occur in -among the cortical parenchyma cells. - -=Phloem.= The phloem contains sieve cells, phloem, parenchyma, and -bast fibres. - -The =sieve cells= are small and with thin, white, angled walls. - -The =phloem parenchyma= cells resemble the sieve cells, but they are -larger. - -The =bast fibres= occur singly or in groups of two or three. The -walls are white, non-porous, and non-striated. - -=Cambium.= The cambium layer is composed of rectangularly shaped -cells, which are frequently obliterated. - -=Xylem.= The xylem contains vessels, wood parenchyma, and medullary -rays. - -The =vessels= are large, rounded cells with thick walls. - -The wood parenchyma consists of thick-walled cells of irregular size -and form. - -The =medullary rays= are tangentially elongated and rectangular in -form. - -=Pith parenchyma.= The pith parenchyma cells are rounded in outline -and as large as the cortical parenchyma cells. - - - POWDERED PINK ROOT - -When the roots and rhizomes of spigelia are powdered (Plate 93) they -show the following structure: - -The epidermal cells are small and brownish on surface view, varying -in size from 13 by 18 micromillimeters to 31 by 40 micromillimeters. -When associated with parenchyma they appear as black masses. The -cortical parenchyma cells are rounded and vary in size from 23 by -26 micromillimeters to 37.5 by 90 micromillimeters. Many of the -cells from the root contain larger quantities of minute single -rounded starch grains varying in size from 1 micromillimeter to 4 -micromillimeters. The larger round single starch grains are found in -both the cortical and pith parenchyma of the rhizome. They vary in -size from 5 micromillimeters to 18 micromillimeters. The conducting -elements are pitted tracheids varying from 10 micromillimeters to 38 -micromillimeters in diameter. A few pitted and annular vessels are -also found. The only fibres occurring are found in the xylem. They -are not a prominent feature of the powder, as their walls break up -into minute fragments. The pith parenchyma varies in size from 13 by -19 micromillimeters to 75 by 82.5 micromillimeters. It is in these -cells that the largest starch grains occur. - -Distinguishing diagnostic characters of the powder: - - 1. Parenchyma with starch. - - 2. Dark masses of epidermal tissue. - - 3. Spigelia should contain starch, and it should not contain - cystoliths, stone cells, or long, white-walled bast fibres. - - - POWDERED RUELLIA ROOT - -When the roots of ruellia root and rhizome are powdered (Plate 94) -they show the following structure: - -[Illustration: PLATE 93 - - POWDERED SPIGELIA MARYLANDICA, L. - - 1. Epidermis and cortical parenchyma. 2. Tracheids and fibres. 3. - Parenchyma cells of the root containing the small starch grains, - longitudinal view. 4. Parenchyma of the rhizome containing the - large starch grams, transverse view. 5. Tracheids. 6. Surface view - of the epidermal cells. 7. Starch scattered through the field. 8 - and 8´. Dark masses of epidermal and underlying tissue.] - -[Illustration: PLATE 94 - - POWDERED RUELLIA CILIOSA, Pursh. - - 1. Short, broad cystoliths from the rhizome, 1´. Long cystoliths - from the root. 2 and 2´. Long, narrow, white-walled bast fibres. 3. - Tracheal tissue from the xylem of the stem. 4. Root parenchyma. 5. - Tracheal tissue from the xylem of the root. 6. Cortical parenchyma - cells from the rhizome with short, broad cystoliths. 7 and 7´. - Long, thick-walled sclerids from the root. 8. Short, broad sclerids - from the stem. 9. Pitted pith parenchyma from the stem with - intercellular space. 10. Parenchyma of the root with sclerid and - cystolith, longitudinal view.] - -The epidermal cells vary from 7.8 by 15.6 micromillimeters to 15.1 -by 16.6 micromillimeters. The cell contents are dark and the walls -are light. A few rows of the outer cortical parenchyma cells of both -the rhizome and the root have dark cell contents and white walls. The -dark contents disappear toward the phloem. The cortical cells vary -from 13.6 by 14.3 micromillimeters to 89.5 by 90.9 micromillimeters. -In the cortical parenchyma cells of the rhizome are found the short, -broad cystoliths measuring up to 52 by 62 micromillimeters. In the -corresponding cells of the root are found the long, narrow cystoliths -which measure up to 68.4 by 187.2 micromillimeters. Scattered -throughout the powder are seen three distinct types of sclerids -(stone cells) which are associated with the cortical parenchyma of -both the stem and the root. Most of them are found, however, in -the roots. First, the short, broad stone cells from the stem basis -have square ends; the walls vary from 13 to 19.5 micromillimeters -in thickness with branching pores which extend toward the adjacent -cell. These sclerids vary in size from 52 by 54.6 micromillimeters -to 45 by 130 micromillimeters. Secondly, the long stone cells from -the root vary from 32 by 96 micromillimeters to 45.5 by 542.5 -micromillimeters with walls 16 micromillimeters thick. The width of -the cell and the thickness of the wall vary but little throughout -their entire length. The third type of stone cell also from the root -has unequally thickened walls and the ends are square or blunt. A few -long, narrow, colorless, thin-walled bast fibres also occur. They -are 13 micromillimeters wide, with walls 3.9 micromillimeters thick. -Annular spiral and pitted vessels are also found scattered throughout -the powder. - -The diagnostic characters of the powder are: - - 1. The short, broad, and long, narrow cystoliths. - - 2. The short, broad, and long, narrow sclerids. - - 3. The long, narrow, thin, white-walled bast fibres. - -In poke root, ipecac, sarsaparilla, and veratrum are raphides. In -belladonna and horse-nettle roots are micro-crystals. In calumba, -stillingea, krameria, licorice, scamony root are prisms. In -saponaria, jalap, althea, spikenard, rumex, rhubarb are rosette -crystals. In pleurisy roots both prisms and rosettes occur. - -In gentian, senega, symphytuns, lovage, parsley, inula, echinacea, -angelica, burdock, and chicory no crystals of any kind occur. Root -hairs occur in cross-sections of sarsaparilla root and false unicorn, -but with these exceptions: root hairs do not occur on roots, because -the younger part of the root with root hairs is not removed from -the soil when the drug is collected. In sarsaparilla root there -are several layers of hypodermal cells; in most roots there are no -hypodermal cells. In the non-woody roots or the roots of herbs the -parenchyma cells form the greater part of the tissues of the root. -In ruellia root are stone cells; in spigelia root and many other -roots there are no stone cells. In ruellia root are bast fibres; in -spigelia, gentian, ipecac, chicory, dandelion, symphytum, and lovage -no bast fibres occur. In all the woody roots there is a periderm -consisting of typical cork cells, as in black haw; or stone cells, as -in asclepias; or of a mixture of lifeless parenchyma, medullary rays, -etc., as in Oregon grape root. - -Woody roots have a phellogen layer which is absent in the non-woody -roots. - -The numbers of layers of cortical parenchyma differ in the same -root according to its age, but for a given root there is a normal -variation. - -The number of layers of cortical parenchyma in proportion to other -cells is less in woody roots. - -In woody roots there is no endodermis. The cambium in these -cases shows clearly between the phloem and the xylem part of the -fibro-vascular bundle. - -In woody roots the wood fibres are well developed and form a large -part of the root, and the medullary rays have pitted side and end -walls. - -The description given above of ruellia root is not typical of all -roots, but the structure represents the greater number of the -elements that it is possible to find in a root. In many roots, for -instance, there are no stone cells, in others no epidermis and no -endodermis. In asclepias, aconite, and calumba stone cells occur. -In symphytum, chicory, dandelion, burdock, elecampane, pyre thrum, -gentian, and senega no stone cells occur. In aconite, althea, -asclepias, belladonna, bryonia, columba, ipecac, jalap, krameria, -sarsaparilla, scamony, stillingea, and rumex are characteristic -starch grains. Symphytum, chicory, dandelion, burdock, elecampane, -and pyrethrum contain inulin, but no starch. In saponaria, gentian, -and senega neither starch nor inulin occurs. - -When studying roots the nature of the epidermis or the periderm must -be considered, as also the number of layers of cortical parenchyma; -the occurrence, distribution, and amount of stone cells when present; -the presence or absence of the endodermis; the occurrence and -structure of bast fibres when present; the nature of the cambium -cells; the width and structure of the medullary rays, the size of the -wood fibres and wood parenchyma, and the nature of the cell contents -and the arrangement of the fibro-vascular bundle. - - - - - CHAPTER II - - STEMS - - -When studying stems it should first be determined whether they were -derived from monocotyledonous or dicotyledonous plants. This fact is -ascertained by determining the type of the fibro-vascular bundle. See -Chapter XI. The next fact to determine is whether the stem is from an -herb or from a woody plant. This fact is readily determined because -herbaceous stems have a true epidermis, masses of collenchyma at -the angles of the stem. The cortical cells contain chlorophyll, and -the pith is very large. Woody stems have a corky layer, a phellogen -layer, and the pith is very small except in the very young woody -stems. - -Having determined these facts, a study should be made of the -arrangement, form, structure, color, and the cell contents of the -different cells in order to determine the species of plant from which -the stem was obtained. - - - HERBACEOUS STEMS - -The great variation in the structure of herbaceous stems is shown -in the cross-sections of spigelia (Plate 95); in ruellia (Plate -96); in the charts of powdered genuine horehound, powdered spurious -horehound, and in the chart of powdered insect flower stems. - - - CROSS-SECTION SPIGELIA STEM - -Spigelia stem (Plate 95) has the following characteristic structure: - -=Epidermis.= The epidermal cells are papillate. - -=Cortex.= The cortical parenchyma cells consist of tangentially -elongated cells which are oval in outline. - -=Phloem.= The phloem consists of sieve cells, phloem parenchyma, and -of bast fibres. - -[Illustration: PLATE 95 - - CROSS-SECTION OF STEM OF SPIGELIA MARYLANDICA, L. - - 1. Papillate epidermis. 4. Phloem. 7. Inner phloem. - 2. Cortical parenchyma. 5. Cambium. 8. Pith. - 3. Bast stereome. 6. Xylem.] - -The =sieve cells= are small, and with thin, white, angled walls. - -The =phloem parenchyma= resembles the sieve cells, but they are -larger. - -The bast fibres are rounded in outline and the walls are thick, -white, non-porous, and non-striated. - -=Cambium.= The cambium cells are rectangular in shape or the walls -are collapsed and the cells indistinct. - -=Xylem.= The xylem contains vessels, wood parenchyma, medullary rays. -The vessels are small and angled, the walls are thick and white. - -=Wood parenchyma.= The cells are variable in size and shape, and -the walls are thick. The medullary ray cells are small, narrow, and -tangentially elongated. - -=Internal Phloem.= External to the pith parenchyma are isolated -groups of internal phloem consisting of sieve cells. - -=Pith Parenchyma.= The pith parenchyma cells are oval in form and -irregularly placed. The cells contain small, simple starch grains. - - - RUELLIA STEM - -The cross-section of ruellia stem (Plate 96) is as follows: - -=Epidermis.= The epidermal cells are variable in shape and very -large. There are no cell contents. - -=Cortex.= The cortex consists of collenchyma and parenchyma cells and -stone cells. - -The =collenchyma cells= have very small, angled cavities and very -thick walls. These cells make up the greater part of the cortex. - -The =cortical parenchyma= cells are variable in size and shape. The -stone cells occur singly or in groups. The walls are thick, white, -porous, and striated, and the central cavity is frequently quite -large. - -=Phloem.= The phloem contains sieve cells, phloem parenchyma, and -bast fibres. - -The =sieve cells= have thin, white, angled walls. - -The =phloem parenchyma= cells are frequently tangentially elongated, -otherwise they resemble the sieve cells. - -The =bast fibres= occur alone or in groups. The walls are thick, -white and porous. - -[Illustration: PLATE 96 - - CROSS-SECTION OF STEM OF RUELLIA CILIOSA, Pursh. - - 1. Epidermis. 2. Collenchyma. 3. Parenchyma. 4. Sclerids. 5. Bast - fibres. 6. Phloem. 7. Cambium cells. 8. Xylem. 10. Pith parenchyma.] - -=Cambium.= The cambium cells are rectangular in shape and the walls -are thin. - -=Xylem.= The xylem contains vessels, wood parenchyma, and medullary -rays. - -The =vessels= are large; the walls are thick, white, and angled. - -The =wood parenchyma= cells are variable in size and shape and the -walls are angled. - -The =medullary ray cells= are radially elongated and rectangular in -shape. - -=Pith Parenchyma.= The pith parenchyma cells are large and rounded in -shape. - - - POWDERED HOREHOUND - -The structure of powdered horehound is shown in Chart 97. The -epidermal cells of the leaf (1) are wavy in outline, the guard cells -are elliptical, the stoma lens-shaped, the epidermis often showing -hairy outgrowth as in the illustration. The epidermal cells of the -petals (2) have irregularly thickened beaded walls. The non-glandular -hairs from the calyx (3); the long, thin-walled, multicellular -non-glandular twisted hairs (4) from the leaves and stems; long, -thin-walled, unicellular hairs (5) from the tube of the corolla; the -glandular hairs (6) with a one-celled stalk and with two secreting -cells divided by vertical walls; the eight-celled glandular hair -(7) as seen in surface and side view; the spiral and reticulated -conducting cells (8); the thick, white-walled fibres from the stem -(9); the pollen grains (10) with nearly smooth walls. - -The diagnostic elements of the U. S. P. horehound are the long, -twisted, multicellular hairs (4), the glandular hairs (7), and the -pollen grains (10). - - - POWDERED SPURIOUS HOREHOUND - -Marrubium peregrinum, which is a related species of horehound -and which is a common adulterant of horehound, has the following -structure (Plate 98): - -[Illustration: PLATE 97 - - POWDERED HOREHOUND (_Marrubium vulgare_, L). - - 1. Epidermis of leaf showing the wavy epidermal cells, stoma, - and a clustered hair. 2. Surface view of the petal epidermis. 3. - Non-glandular hair from the calyx or corolla. 4. Long, thin-walled, - twisted, non-glandular hairs from the leaves and stem. 5. - Unicellular non-glandular hair from the tube of the corolla. 6. - Glandular hairs with a one-celled stalk and with two secreting - cells divided by vertical walls. 7. Surface and side view of the - eight-celled glandular hairs. 8. Conducting cells. 9. Fibres from - the stem. 10. Pollen grains.] - -[Illustration: PLATE 98 - - SPURIOUS HOREHOUND (_Marrubium peregrinum_, L.) - - 1. Surface view of the leaf epidermis. 2. View of the petal - epidermis. 3. Non-glandular multicellular branched hair from - the stem, leaves, or flowers with a few of the lower branches - broken. 4. Broken pieces and branches from the compound hairs - scattered throughout the field. 5. Unicellular glandular hair - with a two-celled stalk. 6. Under-surface view of an eight-celled - glandular hair. 7. Side view of eight-celled glandular hair. 8. - Long, pointed, unicellular, non-glandular hair from the corolla, - the wall irregularly thickened near the apex. 9. Fibres. 10. Pollen - grains, 11. Conducting cells of leaf.] - -[Illustration: PLATE 99 - - POWDERED INSECT FLOWER STEMS (_Chrysanthemum cinerariifolium_, - [Trev.], Vis.) - - 1. Surface view of epidermis. - 2. Cross-section of epidermis. - 3. Hairs. - 4. Fibres. - 5. Cross-section of fibres. - 6. Longitudinal view of pith parenchyma. - 7. Cross-section of pith parenchyma. - 8. Conducting cells.] - -The wavy leaf epidermis (1) with stoma; the beaded wall petal -epidermis (2); the non-glandular, multicellular branched hairs (3) -from the stem leaves or flowers; the broken pieces and branches of -the compound hairs (4) scattered throughout the field; the glandular -hairs (5) with a two-celled stalk; the eight-celled glandular hair -(7) seen in surface view and a side view (8) of a similar hair; the -long, pointed, unicellular non-glandular hair from the tube of the -corolla, the wall irregularly thickened near the apex; the fibres -(9) from the stem; the pollen grains (10) with prominent centrifugal -projections; the conducting cells. - -The diagnostic elements of marrubium peregrinum are the multicellular -branched hairs (3) which occur on all parts of the plant, usually -much broken in the powder, with walls many times thicker than the -walls of the hairs found in U. S. P. horehound; the pollen grains -(10) with centrifugal projections and the stalked glandular hairs (5). - - - INSECT FLOWER STEMS - -Insect flower stems are the chief adulterant of insect flowers. -Until the passage of the insecticide law, it was a common practice -to sell (for insect powder) a mixture of powdered stems and flowers. -Since the passage of the law, the presence of the stems in a powder -is supposed to be declared on the label. In spite of the penalties -attached, their presence in a powder is frequently not declared, -as evidenced by a microscopical examination of the insect powders -obtained in the open market. - -The structure of powdered insect flower stems (Chart 99) is as -follows: - -The epidermal cells of the stems are prominently marked with stoma -and angled, striated wall cells (Fig. 1). On cross-section (Fig. -2) the stem is seen to be made up of epidermal cells with thick -outer and thin side walls (Fig. 2). The T-shaped hairs (Fig. 3) are -longer than those found on any other part of the plant. The fibres -(Fig. 4) are the most characteristic part of the powder. They are -elongated, and the walls are white and slightly porous and of nearly -uniform thickness. They occur free in the field or in groups of two -or more. The cross-section view of these fibres is shown in Fig. 5. -The pith parenchyma (Fig. 6) is abundant and is composed of thick, -porous-walled cells. On cross-section the cells are rounded and are -separated by intercellular spaces. The conducting cells (Fig. 8) vary -from spiral to reticulate. - - - - - CHAPTER III - - WOODY STEMS - - BUCHU STEM - - -The cross-section of a buchu stem (Plate C), 1.6 millimeters -in diameter, shows a few of the epidermal cells modified into -thick-walled, roughish, unicellular trichomes (1). The remaining -epidermal cells have a thick, wavy outer wall (2). Beneath the -epidermis are several rows of cortical parenchyma cells (3) which -extend to the bast bundles and in which are found the secretory -cavities with the thin-walled secretory cells (4). The bast fibres -(5) occur in continuous bands, varying greatly in size; the walls -are whitish and of variable thickness. Inside the bast fibres, the -small irregular sieve cells (6) occur in groups, surrounded by the -phloem parenchyma (8). The radially elongated cells of the medullary -rays (7) extend outward from the xylem, increasing in number in -the outer portions of the wood, and extending nearly to the bast -fibres. No distinct cambium layer is visible. The conducting cells -(9) occur throughout the xylem surrounded by the wood fibres and -wood parenchyma (10). The latter is not very abundant in buchu. The -medullary rays border on the conducting cells and extend outward to -the phloem. The pith parenchyma cells are nearly circular in outline -and often show a perforated end wall when a cell happens to be cut -just above or below that point. - - - MATURE BUCHU STEM - -In Plate 101-A is shown the cork formation or secondary growth as -seen in the older, larger buchu stems. The wavy epidermis (1), -which is the primary epidermis and which has disappeared on many -portions of the stem, has thin side walls and dark cell contents -(2). Next to the epidermal cells occur several rows of peculiarly -arched cork cells with thick, white outer walls (3) and reddish-brown -cell contents (4). The cork cambium (5) is typical in form, and it -has formed one or two layers of phelloderm cells (6) which have -the same form as the cambium cells but with thicker walls. Next to -the phelloderm occur the cortical parenchyma cells. The remaining -structure of the mature stem is identical with that of Fig. 2. - -[Illustration: PLATE 100 - - CROSS-SECTION OF BUCHU STEMS (_Barosma betulina_ [Berg.], - Barth, and Wendl.) - - 1. Hairs. 2. Wavy epidermis. 3. Cortical parenchyma. 4. Secretion - cells and cavity. 5. Group of bast fibres. 6. Sieve cells. 7. - Medullary rays. 8. Phloem parenchyma. 9. Vessels. 10. Wood fibres, - and wood parenchyma. 11. Pith parenchyma.] - -[Illustration: PLATE 101 - - _A._ Cross-section of buchu stem (_Barosma betulina_ [Berg.], - Barth. and Wendl.). 1, Outer wall of epidermis; 2, Cell cavity of - epidermal cell; 3, Wall of cork cell; 4, Cavity of cork cell; 5, - Phellogen layer; 6, Divided phellogen cell changing into a cortical - parenchyma cell; 7, Cortical parenchyma cell. - - _B._ Cross-section of leptandra rhizome (_Leptandra virginica_ - [L.], Nutt.). 1, Parenchyma cells undergoing change in the - composition of their walls; 2, A break in the epidermal tissue; 3, - Parenchyma cells undergoing division.] - - - POWDERED BUCHU STEM - -Powdered buchu stem (Plate 102) has many striking features which -make it easy of identification when mixed with buchu leaves. A -few unicellular, rough, thick, white-walled trichomes (1) occur -distributed throughout the field. They are straight or slightly -curved and vary in length from 40 to 100 microns; in thickness at the -bast they measure from 10 to 22 microns. The central cavity varies -greatly, and in some trichomes seems to have disappeared entirely. -The epidermal cells (2) are very characteristic, occurring singly -or in groups of two or more. The cells from the older stems often -appear reddish brown by transmitted light, while the epidermal cells -from the younger stems appear whitish opaque (porcelain-like). -They are usually six-sided and angular in outline. The cortical -parenchyma cells (3) on transverse view have a rounded cell cavity -and intercellular spaces between the walls. The double walls vary -in thickness, the greatest thickness being about 9 microns. The -parenchyma cells (3) on longitudinal view show square ends and often -contain sphæro-crystalline masses of hesperidin. The thin-walled -sieve cells and the surrounding cells are scarcely ever seen in the -powder. The white-walled pointed stereomes (4) are a characteristic -feature of the powder; they vary greatly in length, in diameter and -in the thickness of their walls. In a number eighty powder the fibres -are mostly broken. The greatest length of the unbroken fibres is -1.25 microns. The thickest wall measured 5 microns and the greatest -observed width was 25 microns. The spiral reticulate and scalariform -thickened conducting cells occur scattered throughout the powder. The -reticulate and scalariform cells usually occur with wood fibres. It -is an interesting fact that the spiral thickening in conducting cells -is usually separate from the side wall and nearly always appears as -indicated at 5. An occasional rosette crystal of calcium oxalate (6) -is seen in the field. The wood parenchyma (7), which makes up a very -small percentage of the xylem, is not readily found in the powder. -The pith parenchyma cells (8) have thick, porous side walls and -perforated side walls. The wood fibres (9) usually occur in masses -surrounding the conducting cells; when occurring singly, the oblique -pores readily distinguish them from the bast fibres. - -[Illustration: PLATE 102 - - POWDERED BUCHU STEMS (_Barosma betulina_ [Berg.], - Barth. and Wendl.). - - 1. Hairs. 2. Epidermal cells, the larger pieces reddish-brown; the - smaller aggregations white. 3. Transverse cortical parenchyma. - 3’ Longitudinal cortical parenchyma with sphæro crystalline - masses of hesperidin. 4. Bast fibres. 5. Spiral, sclariform, and - reticulate vessels. 6. Rosette crystals of calcium oxalate. 7. Wood - parenchyma. 8. Pith parenchyma with porous side and end walls. 9. - Wood fibres.] - -The diagnostic elements of powdered buchu stems are: - -First, trichomes; secondly, reddish-brown and white-angled epidermal -cells; thirdly, the long, white bast fibres. - - - - - CHAPTER IV - - BARKS - - -Barks are all obtained from dicotyledonous plants. In studying -barks there should be ascertained the thickness, arrangement, form, -structure, color, and cell contents of the cells occurring in the -_outer_, _middle_, and _inner_ barks. - -The outer bark includes the cork cells and the phellogen layer. The -middle bark includes all the cells occurring between the phellogen -layer and the beginning of the medullary rays. The inner bark -includes the medullary ray cells and all cells associated with them. -The plan of structure of all barks is similar, but in each species of -plant the structure of the bark is uniform and characteristic for the -species. - -A great number of drugs consist of the bark of woody plants; for this -reason the bark is considered in a separate chapter from the stem. - - - WHITE PINE BARK - -The cross-section of white pine bark (Plate 103) has the following -structure: - -=Outer Bark.= The periderm consists of several layers of -reddish-brown cork cells (1) which are narrow, elongated, and with -thin walls. - -=Middle Bark.= The cells forming the middle bark are parenchyma and -secretion cells. - -The =parenchyma cells= vary greatly in size, form, and thickness of -the walls. The cells beneath the cork cells and around the secretion -cells are tangentially elongated and oval in shape, while the other -parenchyma cells are more irregular in shape. - -The secretion cells are arranged around the schizogenous secretion -cavities. The cells are tangentially elongated, and the walls, which -are slightly papillate, are white. - -=Inner Bark.= The cells forming the inner bark are medullary rays, -parenchyma, sieve cells, and storage cavities. - -[Illustration: PLATE 103 - - CROSS-SECTION OF UNROSSED WHITE PINE BARK (_Pinus strobus_, L.) - - 1. Cork cells of the epidermis. 2. Parenchyma cells filled with - chlorophyl. 3. Intercellular space. 4. Secretion cavity with resin. - 5. Secretion cells. 6, One or more circles of parenchyma filled - with chlorophyl. 7. Parenchyma. 8. Medullary rays. 9. Sieve cells. - 10. Storage cavities.] - -The =medullary rays= form wavy lines. The medullary ray cells are -radially elongated, rectangular in shape, and they contain granular -cell contents. The sieve cells are either square or rectangular in -shape. The walls are thin and white. The storage cavities are either -filled with starch or with prisms and tannin. - - - POWDERED WHITE PINE BARK - -White pine bark (Plate 104) when powdered shows the following -characteristic elements: - -The microscopic structure of a powdered white pine is as follows: The -epidermis (1) consists of reddish-brown masses, irregular in outline. -The outer parenchyma cells are of a bright-green color, owing to the -presence of chlorophyll. (The above elements are not usually found in -the rossed bark.) The parenchyma (3) with starch usually occurs in -longitudinal sections accompanied with sieve cells. Often the tissue -separates transversely, showing the medullary rays (4) with their -granular cell contents (9) and the inner parenchyma cells filled with -starch and the surrounding sieve cells. - -The crystals are nearly perfect cubes and occur singly (5) or in -groups (6). On the longitudinal section of the bark the crystals -occur in parenchyma cells surrounded by a reddish cell content and -form parallel rows which are very characteristic. The resin occurs -either as white, angled fragments (7) in a water mount, or as -globular mass (8) or as reddish-brown pieces (10). The starch is very -abundant and is distributed through the field. The diagnostic grain -is lens-shaped, with a cleft hilum, which is nearly straight, or -slightly curved, and runs parallel to the long diameter of the grain. -The addition of ferric chlorid T. S. will show the presence of tannin -by forming a dark coloration. The identification of the starch is -facilitated by the addition of a weak Lugol’s solution, which imparts -a blue coloration to the starch grain. - -The form, amount, and distribution of the cells composing the bark -differ greatly in different plants. - -In cramp bark the cork and phellogen cells are very large, while in -cascara sagrada the phellogen and the cork cells are very small. - -[Illustration: PLATE 104 - - POWDERED WHITE PINE BARK (_Pinus strobus_, L.) - - 1. Epidermis. 2. Parenchyma cells. 3. Parenchyma with starch. 4. - Medullary rays. 5. Solitary crystals. 6. Solitary crystals and - tannin. 7, 8 and 10. Resin masses. 9. Starch.] - -In canella alba bark the periderm is composed of stone cell cork -or stone cells arranged in superimposed rows, which form the outer -layers of the bark. - -In white oak and most barks from woody trees the periderm consists of -lifeless parenchyma, medullary rays, sieve cells, bast fibres, and in -some cases stone cells and of phellogen cells. - -In young wild cherry, cascara sagrada, and frangula are several -layers of tangentially elongated collenchyma cells with chlorophyll. -In the older barks of the above and in many other barks no -collenchyma cells occur. - -In cramp bark and in tulip tree bark the outer layers of the cortical -parenchyma cells are beaded. In most barks there is no beaded walled -parenchyma. The outer layers of most cortical parenchyma cells are -tangentially elongated while the inner parenchyma cells are mostly -circular in outline. - -In white oak, cascara sagrada and prickly ash are groups of stone -cells; in the cinnamon barks are bands of stone cells; in cinchona -bark are isolated stone cells. In cramp bark, mezerum, elm, and white -pine bark no stone cells occur. - -In frangula, cascara sagrada, cocillina, cinnamon, cinchona, -sassafras, and wild cherry barks the bast fibres occur in groups. -In frangula, cascara sagrada, and cocillina the bast fibres are -surrounded by crystal cells with crystals. - -In sassafras bark mucilage cells occur. In canella alba, white pine, -and sassafras barks secretion cells occur; but in most barks no -secretion cells occur. - -In sassafras bark the medullary ray cells are nearly as broad as -long; in cramp bark they are elongated and oval in shape. In cascara -sagrada, as in most barks, the cells are longer than broad and -rectangular in shape. - -In cascara sagrada the sieve cells are very large; in granatum bark -the sieve cells are very small. - -In cassia cinnamon and in canella alba bark the walls of the sieve -cells have collapsed, with the result that the sieve cells have -become partly obliterated. - -In witch-hazel, mountain maple, willow, and black walnut are found -prisms; in cramp bark, black haw, wahoo, pomegranate, and cotton root -bark are found rosette crystals; in the cinnamon barks are found -raphides; in cinchona bark, micro-crystals. - -In cocillina, frangula, cascara sagrada, white oak, poplar and -Jamaica dogwood barks are found crystal-bearing fibres (Plates 19 and -20). - -When studying barks we must consider the kind, structure, and amount -of the periderm; the nature of the phellogen; the nature and amount -of the cortical parenchyma; the occurrence, distribution, and amount -of stone cells, when present; the occurrence and structure of the -bast fibres; the presence or absence of secretion cells; the width, -distribution, and structure of the medullary rays. - - - - - CHAPTER V - - WOODS - - -Quite a number of drugs consist of the =wood= of woody plants; such -drugs are quassia, red saunders, white sandalwood, and guaiac. - -When studying woods it is necessary to observe the cross, tangential, -and radial sections. Such sections of quassia are shown in Plates -105, 106, and 107. When studying these sections it should be -remembered that while the types of cells forming quassia wood are -similar to the cells forming other woods, still their structure, -arrangement, and amount will vary in a recognizable way in the -different woods. - - - CROSS-SECTION QUASSIA - -Plate 105 is a cross-section of quassia. It has the following -structure: - -=Vessels.= The vessels occur singly or in groups of two to eight -cells. The cells are variable in size and shape. The walls are -yellowish white and porous. - -=Medullary Rays.= The medullary rays vary from one to five cells in -width. - -The =medullary ray cells= are radially elongated and the walls are -strongly porous. - -=Wood Parenchyma.= The wood parenchyma cells have thin, -yellowish-white, angled walls. - -=Wood Fibres.= The wood fibres have thick, yellowish-white, angled -walls. These cells are smaller in diameter than the wood parenchyma -cells. - - - RADIAL SECTION QUASSIA - -The radial section of quassia (Plate 107) is as follows: - -=Vessels.= The vessels appear as in the tangential section. - -=Medullary rays.= The medullary rays vary from ten to twenty cells in -height according to the part of the medullary ray bundle cut across. - -[Illustration: PLATE 105 - - CROSS-SECTION OF QUASSIA WOOD (_Picræna excelsa_ [Sw.], Lindl.) - - 1. Vessels. - 2. Medullary rays. - 3. Wood parenchyma. - 4. Wood fibres.] - -[Illustration: PLATE 106 - -TANGENTIAL SECTION OF QUASSIA WOOD (_Picræna excelsa_ [Sw.], Lindl.) - - 1. Vessel. 2. Wood parenchyma. 3. Wood fibre. 4. End wall of - medullary ray cell. 5. Medullary ray bundle.] - -[Illustration: PLATE 107 - - RADIAL SECTION OF QUASSIA WOOD (_Picræna excelsa_ [Sw.], Lindl.) - - 1. Showing the height and length of the medullary rays and cells. - 2. Cells with starch. - 3. Wood parenchyma and wood fibres.] - -The =medullary ray cells= exhibit their height and length. The walls -of the cells are yellowish white and strongly porous. - -=Wood Parenchyma.= The wood parenchyma cells have yellowish, thin -walls and blunt end walls. - -=Wood Fibres.= The wood fibres have thick, yellowish-white walls, and -the end of the cells are strongly tapering. - - - TANGENTIAL SECTION QUASSIA - -The tangential section of quassia (Plate 106) shows the following -structure: - -=Vessels.= The vessels are very long and broad and the yellow walls -are marked with clearly defined pits. - -=Medullary Rays.= The tangential section shows the cross-section of -the medullary ray bundle and the cross-section of the medullary ray -cell. - -The =medullary ray bundle= varies in width from one to five cells. -The ends of the bundles are always one cell in width, while the -central part of the bundle is frequently five cells in width. - -The =medullary ray cell= varies in size, structure, and shape -according to the part of the cell cut across. The cells cut across -the centre show hollow spaces, but the cells cut just above or below -the end wall show a strongly pitted surface. The cells forming the -end of the bundle are larger than the cells forming the centre of the -bundle. - -=Wood Parenchyma.= The wood parenchyma cells are greatly elongated -and the walls are thin and yellowish white. The ends of the cells are -blunt. - -=Wood Fibres.= The wood fibres are elongated, the walls are thick and -the cells are strongly tapering. - -In quassia, white sandalwood, red sandalwood, and guaiac wood are -characteristic crystals. - -In quassia the vessels are finely pitted, yellowish, and distinct; in -white sandalwood the vessels are coarsely and sparingly pitted and -white translucent; in red saunders the vessels are coarsely pitted, -bright red and distinct. - -When studying woods we must consider the width of the medullary rays, -the structure and cell contents of the medullary ray cells; the -structure, color, and cell contents of the wood parenchyma; also the -wood fibres. - - - - - CHAPTER VI - - LEAVES - - -Leaves collectively constitute the greatest manufacturing plant in -the world. Most of the food, clothing, and medicine used by man -is formed as a result of the work of the leaf. The cell contents, -structure, and arrangement of the different cells of the leaf differ -in a marked degree from the cell contents, structure, and arrangement -of the cells in the other organs of the plant. This accounts for the -presence of the large amount of chlorophyll in the leaf, the presence -of stomata, and the peculiar arrangement of the cells. - -It should be ascertained if the stomata are above, even with, or -below the epidermis; the nature of the epidermal cells, and, when -present, the nature of the hypodermal cells; the number of layers of -palisade parenchyma and whether it is present on both surfaces of the -leaf, and the nature of the outgrowths from the epidermal cells. - - - KLIP BUCHU - -The cross-section of klip buchu (Plate 108) has the following -structure: - -=Epidermis.= The epidermal cells of klip buchu are modified to form -papillæ, the walls are yellowish white, and the papillate portion of -the cell is nearly solid. - -=Hypodermis.= The hypodermal cells are never intact because the -mucilage contained in the cells swells when placed in water and -breaks the thin side walls. - -=Upper Palisade Parenchyma.= The palisade parenchyma is two layers in -thickness. The cells of the outer layer are greatly elongated and are -packed with chlorophyll. The inner layer of palisade cells is more -irregular, and the cells are much shorter than the cells of the outer -palisade layer. - -[Illustration: PLATE 108 - - CROSS-SECTION OF KLIP BUCHU JUST OVER THE VEIN - - _A._ Papillate upper epidermis. - _B._ Hypodermal cells with broken side walls, due to expansion of - mucilage contents. - _C._ Palisade cells, showing two cells filled with chlorophyll. - _D._ Palisade like mesophyll. - _E._ Endodermis. - _F._ Vascular strand of vein. - _G._ Conducting cells with spirally thickened walls. - _H._ Characteristic leaf mesophyll. - _I._ Short, thick palisade cells on the under side of leaf, just - under the vein. - _J._ Under hypodermal cells. - _K._ Papillate under epidermis.] - -=Spongy Parenchyma.= The spongy parenchyma cells are branched; -therefore, large intercellular spaces occur between the cells. - -=Under Palisade Parenchyma.= The palisade cells of the under -epidermis are short and broad, and they contain fewer chlorophyll -grains than the upper palisade cells of the upper epidermis. These -cells occur only under the veins. - -=Under Hypodermis.= The under hypodermal cells are shorter and -broader than the upper hypodermal cells. - -=Under Epidermis.= The under epidermal cells are modified to form -papillæ which are similar to the papillæ of the upper epidermis. - -=Fibro-Vascular Bundle.= The cells composing the vascular bundle are -sieve cells, vessels, and fibres. - -The =sieve cells= are small and the walls are white and angled. - -The =vessels= have thick, white, angled walls. - -The =bast fibres= are rounded in outline and the walls are thick and -white. - -=Endodermis.= The endodermal cells encircle the fibro-vascular -bundles. The cells are large, thin-walled, and oval in shape. - -=Secretion Cells.= Near the edges of the leaf are schizogenous -secretion cavities surrounded by thin-walled secretion cells. - - - POWDERED KLIP BUCHU - -When the leaf is powdered (Plate 109), the cells are quite as -characteristic in appearance. The upper epidermal cells (1) have -thick-beaded, yellowish-white walls and papillate outer walls. No -stomata occur on the upper surface. The under epidermis (2) with -numerous stomata, is surrounded by the characteristic guard cells. -The end walls are beaded as on the upper surface. The palisade cells -(3) appear as in the cross-section. The conducting cells (4 and 4) -are of the spiral and pitted type. The papillæ (5 and 5) are very -abundant in the powder and very characteristic. The fragments of the -epidermis (6) are also abundant. The mesophyll (7) is characteristic, -as it retains its form when powdered. The fibres (8) are usually -associated with the conducting cells; occasionally they are found -free as in the illustration. - -[Illustration: PLATE 109 - - POWDERED KLIP BUCHU - - 1. Upper epidermis. 2. Under epidermis. 3. Palisade cells with - chlorophyll. 4 and 4. Conducting cells. 5 and 5. Papillæ. 6. - Fragments of the epidermis. 7. Mesophyll. 8. Fibres.] - - - MOUNTAIN LAUREL - -=Epidermis.= The epidermal cells of mountain laurel are occasionally -modified, as unicellular hairs (Plate 110, Fig. 1), particularly in -the region of the veins. The ordinary epidermal cells have thick -outer walls and thin inner walls. Beneath many of the epidermal cells -are large air-spaces. - -=Upper Palisade Parenchyma.= The palisade parenchyma vary from four -to five layers. The inner palisade cells are shorter and broader than -the outer layer of cells. - -=Parenchyma.= The parenchyma cells (Fig. 4) are rounded in form -and they are arranged in the form of columns which are one cell in -thickness above, but two to three cells in thickness near the under -epidermis. Between each chain of cells is a larger intercellular -space (Fig. 6). In a few of the cells are large rosette crystals. - -=Under Epidermis.= The under epidermal cells are uniformly smaller -than the upper epidermal cells. - -It is thus seen that mountain laurel leaf has no hypodermal cells; -no spongy parenchyma; no under palisade cells; no under hypodermal -cells, and no secretion cavities. - - - TRAILING ARBUTUS - -=Epidermis.= The epidermal cells of the trailing arbutus (Plate 111, -Fig. 2) are variable in size. Many of the cells are modified, as -guard cells (Fig. 1). - -=Parenchyma.= The parenchyma cells are round and they are compactly -arranged (Fig. 3) on the upper side of the leaf, but on the under -side they are arranged in round, small, intercellular spaces (Fig. -5). In some of the intercellular spaces are rosette crystals (Fig. 7). - -=Under Epidermis.= The under epidermal cells are smaller than the -upper epidermal cells. - -It will be seen that the structure of trailing arbutus leaf is very -simple and that its structure is different from that of klip buchu -and mountain laurel. - -The structure of powdered leaves is very variable, yet characteristic -for a given species. The leaves from the insect flower plant are -collected with the stems, and ground and sold as a substitute for -insect flowers. These leaves, when powdered, show the following -structure (Plate 112): - -[Illustration: PLATE 110 - - CROSS-SECTION MOUNTAIN LAUREL (_Kalmia latifolia_, L.) - - 1. Hair. 2. Epidermis. 3. Palisade parenchyma. 4. Parenchyma. 5. - Under epidermis. 6. Intercellular space. 7. Rosette crystal. 8. - Chlorophyll.] - -[Illustration: PLATE 111 - - CROSS-SECTION TRAILING ARBUTUS LEAF (_Epigæa repens_, L.) - - 1. Stomata. 2. Epidermis. 3. Parenchyma. 4. Cell with chlorophyll. - 5. Intercellular space. 6. Under epidermis. 7. Rosette crystal.] - -Both the upper and lower epidermis have stomata (Figs. 1 and 2), but -they differ in that the surrounding cells of the upper epidermis -are wavy, while the corresponding cells of the under epidermis are -similar, though the under epidermis has many attached hairs (Figs. -3 and 4). The T-shaped hairs form the most abundant element of the -powder. They are similar in structure to those found on the scales -and stem. Fragments of the mesophyll have round cells and contain -chlorophyll (Fig. 6). The conducting cells are spiral or reticulate. - -The different cells of the leaf differ greatly in structure, in -amount, and in arrangement. In uva-ursi, boldus, pilocarpus, -eucalyptus, and chimaphila leaves the outer walls of the epidermal -cell is very thick. In uva-ursi leaves this thick wall appears bluish -green when viewed under low power of the microscope. - -In belladonna, stramonium, henbane, peppermint, spearmint, digitalis, -and horehound, the outer wall of the epidermal cells is thin. - -In witch-hazel, stramonium, coca, phytolacca, and peppermint there is -a single layer of palisade parenchyma on the upper surface only of -the leaf. - -In senna there is one layer of palisade parenchyma on the upper and -one layer on the under side of the leaf. In matico and tea leaves -there are two layers of spongy parenchyma on the upper side of the -leaf. - -In chestnut leaves there are three layers of palisade parenchyma on -the upper side of the leaf. - -In eucalyptus leaves the entire central part of the leaf, with the -exception of the secretion cells and fibro-vascular bundle, is made -up of the palisade parenchyma. - -In some leaves no palisade parenchyma occurs. Trailing arbutus (Plate -111) is an example of such a leaf. - -In stramonium leaves the spongy parenchyma is strongly branched; in -mountain laurel the spongy parenchyma is mostly non-branched and -circular in form, as in trailing arbutus (Plate 111, Fig. 3), and as -occurs in the midrib portion of most leaves. - -[Illustration: PLATE 112 - - POWDERED INSECT FLOWER LEAVES - (_Chrysanthemum cinerariifolium_ [Trev.], Vis.) - - 1. Upper epidermis. 2. Under epidermis showing stoma and hair - scar. 3. Cross-section of under epidermis with attached hair. 4. - Cross-section of upper epidermis. 5. Hairs. 6. Mesophyll with - chlorophyll bodies. 7. Conducting cells.] - -In stramonium and chestnut are found rosette crystals. In henbane, -coca, and senna are found prisms. In belladonna, scapola, and -tobacco leaves are found micro-crystals. In most leaves no crystals -occur. In witch-hazel and tea leaves stone cells occur, but in most -leaves there are no stone cells. In eucalyptus, thyme, jaborandi, -buchu, rosemary, and white pine leaves are secretion cells; while -in belladonna, stramonium cells occur. In senna and coca leaves are -crystal-bearing fibres; most leaves do not have crystal-bearing -fibres. - -In chimaphila and uva-ursi there are no outgrowths from the epidermal -cells. - -In senna, witch-hazel, chestnut, and coca, numerous non-glandular -hairs occur on the epidermis. In tobacco, belladonna, henbane, -pennyroyal, peppermint, and spearmint both glandular and -non-glandular hairs occur on the epidermis. - -When studying leaves there should be considered the absence or -presence of outgrowths and their nature; the nature of the epidermis -and, when present, the number of layers of the hypodermis; the nature -of the stoma, whether raised above, even with, or below the level -of the epidermis; the number of layers, and the distribution, when -present, of the palisade parenchyma; the form and amount of the -spongy parenchyma; the absence or presence of secretion cells; the -nature and form of the fibro-vascular bundles, and the nature and -amount of the organic and inorganic cell contents. - - - - - CHAPTER VII - - FLOWERS - - -The histological structure of flowers is readily seen in the powder; -therefore, in studying flowers, it is not necessary to section -the various parts. Each part of the flower should be isolated and -powdered separately and each separated part studied. In each case -the powders will contain surface, cross-, and radial sections of the -parts powdered. While studying flowers, special attention should be -given to the pollen grains, to the papillæ of the petals, to the -papillæ of the stigma, and, in certain flowers, to the style tissue. -In the composite flowers special attention should also be given to -the involucre scales, to the scales of receptacle, and, when present, -to the pappus. In addition, attention must be given to secretion -cavities, as in cloves. - - - POLLEN GRAINS - -Pollen grains are one of the most characteristic elements found in -powdered flowers, because they are so small that they are not broken -up when the drug is milled. - -The two principal groups of pollen grains are, first, those with -non-spiny walls (Plate 113); and, secondly, those with spiny walls -(Plate 114), as shown in the two charts. - -In lavender flowers the pollen grains have six constrictions of the -outer wall. This wall is slightly striated and the cell contents are -granular. - -In clover flowers the pollen grains are mostly rounded in outline, -the wall is uniformly thickened, and cell contents are coarsely -granular. - -In belladonna flowers the pollen grains terminate in three blunt -points. - -In Spanish saffron the pollen grains are spherical and the cell -contents are granular. - -[Illustration: PLATE 113 - - SMOOTH-WALLED POLLEN GRAINS - - 1. Cloves (_Eugenia caryophyllata_, Thunb.). 2. Santonica - (_Artemisia pauciflora_, Weber). 3. Elder (_Sambucus canadensis_, - L.). 4. Century minor (_Erythræa centaurium_ [L.], Pers.). 5. Pichi - (_Fabiana imbricata_, R. and P.). 6. Cyani. 7. Lavender (_Lavandula - officinalis_, Chaix.). 8. Clover (_Trifolium pratense_, L.). 9. - Belladonna (_Atropa belladonna_, L.). 10. Spanish saffron (_Crocus - sativus_, L.).] - -[Illustration: PLATE 114 - - SPINY WALLED POLLEN GRAINS - - 1. Anthemis (_Anthemis nobilis_, L.). - 2. Arnica (_Arnica montana_, L.). - 3. Calendula (_Calendula officinalis_, L.). - 4. Cassia flowers. - 5. American saffron (_Carthamus tinctorius_, L.). - 6. Blue malva flowers (_Malva sylvestris_, L.).] - -The non-spiny-walled pollen grains differ not only in microscopic -appearance, but also in size. Clove pollen grains are the smallest, -while Spanish saffron pollen grains are the largest. - - - NON-SPINY-WALLED POLLEN GRAINS - -In cloves the pollen grains show a six-sided, angled cavity and an -outer wall which terminates in three slightly pointed, narrowly -notched portions, separated by nearly straight walls. - -In santonica the pollen grains have smooth, unequally thickened -walls, which are strongly constricted at three points, the outline -resembling three half-circles placed together. - -In elder flowers the pollen grains appear circular or three-parted. -The wall is of nearly uniform thickness, even at the constricted part -of the grain. - -In century minor the pollen grains show three pronounced -restrictions. The wall at these points is very thin. In pichi -flowers the pollen grains are either circular or three-sided and -three-pointed. Inside of each point there is a nearly white pore. In -some of the grains the pollen tube has grown out of one of the pores. - -In cyani flowers the pollen grains are longer than broad and the cell -contents appear to be divided into two end portions and an elevated -middle portion. - - - SPINY-WALLED POLLEN GRAINS - -In anthemis the pollen grains have unequally thickened walls -constricted in three places. The spines are short, broad at the base, -and sharp-pointed. - -In arnica flowers the pollen grains show three light-colored pores -and numerous short spines. - -In calendula flowers the pollen grains show one or more pores, -typically three pores. These pores appear as white spots, and the -wall immediately over the pore is smooth and thinner than the -remaining part of the wall; the spines are very numerous. - -In cassia flower pollen grains the outer wall is extended into a -number of rounded projections which are frequently arranged in sets -of fours. - -In American saffron flowers the pollen grains show one, two, or three -light-colored pores; the spines are short and broad. - -In blue malva flowers the pollen grains are spherical and the outer -wall extends into numerous spinelike projections. - -It will be observed that the spiny-walled pollen grains differ -greatly in size, the smallest being the pollen grain of anthemis and -the largest being the pollen grain of blue malva flowers. - -In matricaria are numerous, greenish-brown, spiny-walled pollen -grains. In anthemis are multicellular, uniseriate non-glandular hairs -with three or four short, broad, yellow-walled basal cells and a -greatly elongated, thin, gray-walled apical cell. - -In arnica are multiseriated branched hairs of the pappus, and -numerous large, yellowish, spiny-walled pollen grains. - - - STIGMA PAPILLÆ - -The =papillæ of the stigma= of most flowers form a characteristic -element even when the flower is powdered. In the case of composite -flowers the papillæ of the disk and ray flowers differ. In American -saffron the papillæ of the style differ in a recognizable way from -the papillæ of the stigma. - -The papillæ of the stigma of the ray and disk flowers of arnica, -anthemis, matricaria, and insect flowers differ greatly. Even the -papillæ of the stigma of the ray and disk flowers differ. In all -cases observed the papillæ of the ray flowers are smaller than the -papillæ of the disk flowers. - -The papillæ of the stigma of saffron (Plate 115, Fig. 3) are long and -tubular. These papillæ are nearly uniform in diameter, and the apex -is blunt and rounded. The wall is slightly granular in appearance. -The papillæ of the stigma of American saffron (Plate 116, Fig. 2) are -short and tubular. Each papilla is broadest at the base and tapers to -a slender point. The papillæ of that part of the style which emerges -from the corolla (Plate 116, Fig. 1) are large and curved, and the -walls are very thick. The apex of the papilla is frequently solid. - -The papillæ of the stigma of the ray flowers of anthemis (Plate 117, -Fig. 1) have thin, slightly striated walls; while the papillæ of the -stigma of the disk flowers (Plate 117, Fig. 2) are longer, the walls -are thicker, and the cell content is denser. - -[Illustration: PLATE 115 - - PAPILLÆ - - 1. Arnica ray flowers (_Arnica montana_, L.). - 2. Insect flower disk (_Chrysanthemum cinerariifolium_ [Trev.], Vis.). - 3. True saffron (_Crocus sativus_, L.).] - -[Illustration: PLATE 116 - - PAPILLÆ OF STIGMAS - - 1. Stigma papillæ of American saffron (_Carthamus tinctorius_, L.) - from that part of the style that emerges from the corolla. - 2. Papillæ from the upper part of the stigma of American saffron. - 3. Papillæ of the stigma of the disk flowers of arnica (_Arnica - montana_, L.).] - -[Illustration: PLATE 117 - - PAPILLÆ OF STIGMAS - - 1. Stigma papillæ of the ligulate flowers of anthemis (_Anthemis - nobilis_, L.). - 2. Stigma papillæ of the tubular flowers of anthemis. - 3. Stigma papillæ of the ligulate flowers of matricaria - (_Matricaria chamomilla_, L.). - 4. Stigma papillæ of the disk flowers of matricaria. - 5. Stigma papillæ of the ligulate flowers of insect flower - (_Chrysanthemum cinerariifolium_ [Trev.], Vis.).] - -The papillæ of the stigma of the ray (Plate 117, Fig. 3) and disk -flowers (Plate 117, Fig. 5) of matricaria are similar in structure, -but the papillæ of the disk flowers are larger. - -The papillæ of the stigma of the ligulate flowers of insect flowers -(Plate 117, Fig. 5) are tubular; the walls are striated, and in each -papilla there is a small yellow globule, while the papillæ of the -disk flowers (Plate 115, Fig. 2) are long and tubular, and the walls -are thick. - -The papillæ of the stigma of the ray flowers of arnica (Plate 115, -Fig. 1) are very short and tubular. The walls are thin and the cell -contents appear as small, bright-yellow globules, while the papillæ -of the stigma of the disk flowers (Plate 116, Fig. 3) are broadest at -the base, the apex is pointed, and the yellow globules are larger. - -The =solitary= hairs are divided into the branched and non-branched -hairs. - - - POWDERED INSECT FLOWERS - -The microscopic examination of insect powder is difficult for the -reason that there are so many elements to be constantly kept in mind. -The parts of the flower which contribute characteristic cells are the -stem, involucre, ray flowers, disk flowers, and the receptacle. In -each of these parts there are many different types of cells. - -There are practically two types of flowers found in insect powder of -commerce: first, closed or immature flowers, and secondly, open or -mature flowers. As explained above, the half-open flowers consist -largely of the two above-named varieties. Let us first consider the -structure of the closed insect flowers as illustrated in Plate 118. - -[Illustration: PLATE 118 - - POWDERED CLOSED INSECT FLOWER - (_Chrysanthemum cinerariifolium_, [Trev.] Vis.) - - 1. Edge of scale. 2. Fibre of scale. 3. Hairs. 4. Upper epidermis - of ray flower. 5. Under epidermis of ray flower. 6. Cross-section - of ray petal. 7. Parenchyma of ray flowers with crystals. 8. Lobe - of disk petal. 9. Filament tissue. 10. Calyx tissue, 11. Lobe of - stamen. 12. Pollen. 13. Papillæ of stigma. 14. Secretion cavity - with surrounding cells. 15. Parenchyma of the receptacle.] - -The involucre has many characteristic cells. The more prominent -ones seen in the powder are the edge of the scale with the attached -hair (Fig. 1). These hairs (Fig. 3) are T-shaped. The terminal cell -is expanded laterally, and it terminates in two points. Connecting -the terminal cell with the epidermis are two or three cells which -are slightly longer than broad. In the powder the terminal cell is -usually attached to fragments only of the supporting cells. Fibres of -the bracts have thick, wavy, porous walls, and they have a tendency -to occur in masses. The upper epidermis (Fig. 4) of the ray-flower -petal is prominently papillate. The under epidermis consists of -wavy cells without papillæ. Another view of the papillæ is shown in -Fig. 6. The parenchyma of the ray flowers (Fig. 7) contain cubical -crystals. The lobe of the disk-flower petal (Fig. 8) is papillate at -the end, the terminal cells have thick outer and thin inner walls. -The filament tissue (Fig. 9) is composed of nearly square cells. The -calyx tissue (Fig. 10) is made up of thin-walled cells with slightly -papillate margins. The lobe of the stamen (Fig. 11) consists of -nearly uniform epidermal cells which are in contact throughout their -long diameter, while the hypodermal cells are thin-walled and angled. -The pollen grains (Fig. 12) are dark yellowish green, thin, and the -wall does not appear perforated by pores. The papillæ of the stigma -(Fig. 13) are clustered, club-shaped, and nearly white in color. They -are usually found detached in the powder. All parts of the pistil -contain secreting cells, but the most conspicuous secreting cavities -(Fig. 14) are those of the ovary. These cavities appear brownish in -color and are surrounded by small cells which appear indistinct on -account of the great number of superimposed cells. The parenchyma of -the receptacle occurs in fragments which have strongly marked porous -walls. - - - OPEN INSECT FLOWERS - -Many of the structures of open insect flowers (Plate 119) are -similar to those found in the closed flower. There is practically -no difference in the edge of the scale (Fig. 1); or the fibre of -the scale (Fig. 2); or the T-shaped hairs (Fig. 3); or the upper -epidermis of the ray flower (Fig. 4); or the under epidermis of the -ray flower (Fig. 5); or the cross-section of the ray petal (Fig. -6); or the lobe of the disk petal (Fig. 7); or the filament tissue -(Fig. 8); or the lobe of the stamen (Fig. 9); or the papillæ of -the stigma (Fig. 12); or the parenchyma of the receptacle (Fig. -15). The difference in structure is found, first, in the involucre -scales, which are more fibrous than the scales of the closed flowers; -secondly, in the pollen (Fig. 11), which is less abundant than in the -closed flower; it is also lighter in color and usually shows the wall -perforated by three pores; thirdly, the outer layers of the achene -consist of thick, porous-walled stone cells (Fig. 13), which occur -singly or in groups; fourthly, the secretion cavity is broader and -darker in color (Fig. 14). These differences enable one at once to -distinguish between the closed and open insect flowers. Now, since -the half-closed flowers consist almost wholly of a mixture of equal -parts of closed and open flowers, it follows that the elements of -these two flowers will be mixed in about equal proportions. Thus -we are able to distinguish microscopically the three commercial -varieties of insect powder--namely, closed insect flowers, open -insect flowers, and half-open insect flowers. - -[Illustration: PLATE 119 - - POWDERED OPEN INSECT FLOWER - (_Chrysanthemum cinerariifolium_, [Trev.] Vis.) - - 1. Edge of involucre scale. 2. Fibres of involucre scale. 3. - Hairs. 4. Upper epidermis of ray flower. 5. Under epidermis of ray - flower. 6. Cross-section of ray petal. 7. Lobe of disk flower. 8. - Filament tissue. 9. Lobe of stamen. 10. Calyx tissue, 11. Pollen. - 12. Papillæ of the stigma. 13. Stone cells from the achene and - cross-section of achene. 14. Secretion cavity with surrounding - cells. 15. Parenchyma of the receptacle.] - -Insect flowers are the most valuable vegetable insecticide known; yet -much of its effectiveness is destroyed by the adulterants which are -so readily identified by the compound microscope. - - - POWDERED WHITE DAISIES - -A common adulterant found in open insect flowers is the flower-heads -of European daisy (_C. leucanthemum_). Examination of powdered -flowers exported from Europe shows that the entire flower-head is -ground and mixed with the insect flowers. In the cheaper varieties -of open flowers, only the tubular flowers are added after they have -been separated from the heads by crushing and sifting. These tubular -flowers so closely resemble the tubular flowers of the true insect -flowers that it is practically impossible to distinguish between them -macroscopically. The quickest and surest way to identify them is -to reduce a portion of the flowers to a fine powder and examine it -microscopically. - -Certain structures of the white daisies (Plate 120) are somewhat -similar to those found in insect flowers. These structures are the -papillæ of the ray petal (Figs. 3, 5, and 13), the lobe of the disk -petal (Fig. 14), and the lobe of the stamen and the pollen (Fig. 8). - -The differences are as follows: The under epidermis of the ray -flowers is composed of wavy cells which are more elongated than the -ray flowers of the under epidermis of the ray petal of insect flower. -The filament tissue is made up of slightly beaded cells instead of -smooth-walled cells. The papillæ of the stigma are smaller than the -papillæ of insect flowers. The most striking difference is found -in the structure of the achene. The epidermal tissue of the achene -is composed of palisade cells (Fig. 10), which in the mature form -have thick white walls and scarcely any cavity. These cells swell -perceptibly when placed in water. The other striking feature of the -achene is the bright red resin masses which occur free in the field. -Even a small trace of daisies in insect powder can be identified. - -[Illustration: PLATE 120 - - POWDERED WHITE DAISIES (_Chrysanthemum leucanthemum_, L.) - - 1 and 2. Scale tissue. 3, 5 and 13. Papillæ of petals. 4. Scale - tissue. 6. Lobe of ray petal. 7. Filament tissue. 8. Pollen. 9. - Papillæ of stigma. 10. Palisade cells of achene. 11. Resin masses. - 12. Parenchyma of receptacle. 14. Lobe of dish petal.] - -When studying flowers there should be considered the number and -structure of pollen grains; the nature of the papillæ of the stigma -and the petals; the nature of the hairs of the corolla and calyx, -when present. In the composite flowers we should also consider the -structure of the involucre scales, and, when present, the structure -of the receptacle scales, as in the case of anthemus, and of the -pappus hairs, as in the flowers of arnica, boneset, grindelia, and -aromatic goldenrod. - - - - - CHAPTER VIII - - FRUITS - -There is great variation in the structure of fruits, such a -variation, in fact, that no one fruit has a structure typical of all -the other fruits. Each fruit, however, has a pericarp and one or more -seeds. The amount and structure of the cells forming the pericarp -and the seeds of fruits differ in different fruits, but for each -fruit there is a normal amount of, and a characteristic, cellular -structure. Nearly all the important medicinal fruits are cremocarps -or umbelliferous fruits. - -The plan of structure of cremocarps is similar, but they all have a -different cellular structure. The epidermis may be simple or modified -as papillæ or hairs. The secretion cavities may be absent (conium), -or, when present, variable in number--cultivated celery seed has six, -wild celery seed up to twelve, and anise up to twenty. The vascular -bundles may be large or small. The endocarp cells may be two or more -layers in thickness. The spermoderm may be thin or thick. - -The endosperm cells may vary in size and the cell contents may vary. - - - CELERY FRUIT - -The fruit of celery (Plate 121), like other umbelliferous fruits, is -composed of the pericarp and the seed. - -The pericarp is composed of epicarp cells, mesocarp cells, endocarp -cells, and in each rib a vascular bundle. The seed is composed of -the spermoderm, endosperm, and embryo. Each of these parts has a -characteristic structure. - -=Epicarp=. The cells of the epicarp (Fig. 1) are papillæ and the -outer wall is striated. The papillæ do not show, however, unless -the cell is cut across the centre, which is the point at which the -papillæ are located. - -[Illustration: PLATE 121 - - CROSS-SECTION OF CELERY FRUIT (_Apium graveolens_, L.) - - 1. Epicarp. 2. Mesocarp. 3. Vascular bundle. 4. Endocarp. 5. - Spermoderm. 6. Endosperm. 7. Secretion cavity.] - -[Illustration: PLATE 122 - - DIAGRAMMATIC DRAWING OF THE - - 1. Cross-section of wild celery seed (_Apium graveolens_, L.). - 2. Cross-section of cultivated celery seed (_Apium graveolens_, L.).] - -=Mesocarp=. In the rib part of the mesocarp (Fig. 2) is a vascular -bundle, and between the ribs one or more secretion cavities. The -vascular bundles are small and are surrounded by irregular-shaped -mesocarp cells. - -The =secretion cavities= (Fig. 7) are oval in form and the tissue -bordering the cavity is reddish brown in color. The mesocarp cells -around the secretion cavities are more elongated than the other -mesocarp cells. - -=Endocarp=. The endocarp cells are three layers in thickness. These -cells are elongated transversely (Fig. 4). - -=Spermoderm=. The cells of the spermoderm are indistinct, compressed, -and dark brown in color (Fig. 5). - -=Endosperm=. The endosperm cells (Fig. 6) make up the greater part -of the fruit. The walls which are common to two cells are thick, -non-beaded, and non-pitted, and the cavities of the cells are filled -with aleurone grains. - -=Embryo=. The embryo cells, which show only in certain sections, are -similar to endosperm cells. - -In anise, hops, sumac, and cumin fruits are characteristic hairs. - -In star anise, sabal, allspice, cubeb, pepper, juniper, buckthorn, -and phytolacca fruits are stone cells. - -In cubeb, pepper, and cardamon are characteristic masses of aggregate -starch. - -In sabal, allspice, and juniper are characteristic secretion cells. - -In all the umbelliferous fruits, with the exception of conium, are -yellow to brown secretion cavities. - -In cubeb and pepper is aggregate starch. Colocynth contains many -single and double spiral vessels. - -Bitter orange contains solitary crystals and spongy parenchyma. - -When studying fruits we must consider the nature of the epicarp -cells--whether simple or modified as papillæ or hairs; the form and -structure of the mesocarp cells; the number, size, and structure of -the vascular bundle; the size and number of the secretion cells or -cavities; the number of layers and the structure of the endocarp -cells; the number of layers of stone cells--when present; the color -and width of the spermoderm layer; the structure and cell contents of -the endosperm cells; the nature of the embryo cells, and the nature -of the cell contents. - - - - - CHAPTER IX - - SEEDS - - -Seeds are very variable in structure, so much so, in fact, that -scarcely any two seeds have a similar structure. It is necessary, -therefore, when examining seeds, to compare the structure of the seed -under examination with authentic plates or with the section of a -genuine seed. The layers of the seed are the spermoderm, perisperm, -endosperm, and embryo. In some seeds the spermoderm forms the greater -part of the seed; in others the perisperm is greatest in amount; -in still others the cotyledons make up most of the seed, as in the -mustards. The cells forming these different layers differ in form, -structure, and number; therefore it is not difficult to distinguish -and to differentiate between the different seeds when viewed as a -section or as a powder. Almond is studied because it has most of the -layers and cells found in seeds. - - - SPERMODERM - -The =spermoderm= is the thin, brown, granular-appearing skin of the -almond. The layers of the spermoderm are the epidermis, the hypoderm, -the middle layers, and the inner epidermis. - -The =epidermis= consists of radially elongated, thick-walled stone -cells which occur alone or in groups of two or more, but seldom as -a continuous layer. The upper or outer part of the stone cells is -non-porous, but the inner walls are strongly porous (Plate 123, Fig. -1). - -The =hypoderm=. The cells forming the hypoderm are compressed, the -wall structure is practically indistinguishable, and the whole mass -is reddish brown (Plate 123, Fig. 2). - -Occurring in this brown layer are several vascular bundles (Plate -123, Fig. 3). - -[Illustration: PLATE 123 - - CROSS-SECTION SWEET ALMOND SEED - - 1. Epidermis. 2. Hypoderm. 3. Vascular bundle. 4. Middle layer. 5. - Inner epidermis. 6. Endosperm. 7. Outer layer of the embryo. 8. - Inner layers of the embryo.] - -The =middle layers=. The cells forming the middle layers (Fig. 4) -have thin, wavy, light-colored walls which are frequently compressed, -and it is with much difficulty that their outlines are made out. - -The =inner epidermis=. The cells forming the inner epidermis are -rectangular in form, and they contain reddish-brown cell contents -(Plate 123, Fig. 5). - - - ENDOSPERM - -The =endosperm=. The cells forming the endosperm are large, -rectangular in outline, usually one layer thick, and they contain -aleurone grains. - - - EMBRYO - -The =embryo=. The cells forming the outer layer of the embryo are -smaller than the inner layers, and they are immediately inward from -the layer of endosperm cells (Plate 123, Fig. 7). - -The cells forming the greater part of the embryo are large, rounded, -and they contain aleurone grains and fixed oil (Plate 123, Fig. 8). - -In white and black mustard are characteristic mucilage and palisade -cells. - -In mix vomica, stropanthus, and St. Ignatius’s bean are -characteristic hairs. - -In physostigma and kola are characteristic starch grains. - -In henbane, capsicum, stramonium, lobelia, and belladonna seeds are -characteristic epidermal cells. - -In areca nut, colchicum, saw palmetto, and nux vomica are -characteristic thick-walled, reserve cellulose cells. - -In cardamon seed are aggregate starch masses with irregular outlines. - -In bitter and sweet almond, linseed, pepo, and stropanthus are -aleurone grains. - -In bitter and sweet almonds are stone cells. - -In linseed, quince seed, and in white and black mustard are epidermal -cells with mucilaginous walls and contents, etc. - - - - - CHAPTER X - - ARRANGEMENT OF VASCULAR BUNDLES - - -Having familiarized ourselves with the different types of mechanical -and conducting cells, we shall now consider the different ways -in which these cells are associated to form the =vascular= and -=fibro-vascular bundles=. - -The simplest form of the vascular bundle occurs in petals, floral -bracts, and leaves. In these parts the vascular bundle is made up of -conducting cells only. - -In the great majority of cases, however, the conducting cells are -associated with mechanical cells to form the fibro-vascular bundle. - -The fibro-vascular bundle is made up of, first, the =phloem=, -which consists of sieve tubes, companion cells, bast fibres, and -parenchyma; secondly, of the =xylem=, composed of vessels and -tracheids, wood fibres and wood parenchyma; thirdly, of medullary -rays (restricted to certain types); and fourthly, of the bundle -sheath (restricted to certain types). - - - TYPES OF FIBRO-VASCULAR BUNDLES - -There are three well-defined types of the fibro-vascular bundle, -namely, the =radial=, the =concentric=, and the =collateral= types. - - - RADIAL VASCULAR BUNDLES - -The radial type of bundle is met with most frequently in -monocotyledonous roots. - -In this form (Plate 114) the xylem forms radial bands of tissue -which alternate with isolated groups of phloem. The space between -the phloem and xylem is filled in with either parenchyma or fibres, -or both. In some cases the vessels of the xylem meet in the centre -of the root, while in other cases the centre of the stem is occupied -by pith parenchyma. Each bundle is surrounded by parenchyma cells, -and in iris, calamus, and veratrum, rhizomes, and endodermis, -surrounds the bundles located in the centre of the stem, consisting -of thin-walled (mechanical) cells. - -[Illustration: PLATE 124 - - CROSS-SECTION OF A RADIAL VASCULAR BUNDLE OF SKUNK CABBAGE ROOT - (_Symplocarpus fœtidus_ [L.], Nutt.) - - 1. Vessels. - 2. Bundle sheath. - 3. Parenchyma. - 4. Sieve cells.] - -[Illustration: PLATE 125 - - CROSS-SECTION OF A PHLOEM-CENTRIC BUNDLE OF CALAMUS RHIZOME - (_Acorus calamus_, L.) - - 1. Vessels. - 2. Sieve cells. - 3. Phloem parenchyma. - 4. Parenchyma surrounding the bundles.] - -In sarsaparilla root, the pith is composed of thick-walled, porous -pith parenchyma cells with starch. Outside the pith are arranged -radial bands of oval vessels which decrease in size toward the -periphery. Between the ends of these bands occur isolated groups of -sieve cells. - -Surrounding the sieve cells and vessels are thick-walled, angled -fibres. - -External to these cells is an endodermis composed of lignified -brownish-colored cells one layer in thickness. - - - CONCENTRIC VASCULAR BUNDLES - -There are two principal types of the concentric bundle, namely, -xylem-centric, in which the xylem is centric and the phloem is -peripheral, as in veratrum root; and phloem-centric (Plate 125), in -which the phloem is centric and the xylem peripheral, as in calamus -rhizome. - - - COLLATERAL VASCULAR BUNDLES - -There are three types of collateral vascular bundles--namely, closed -collateral, bi-collateral, and open collateral. - -In the closed collateral bundle the phloem and xylem are not -separated by a cambium layer, and in many cases the bundle is -surrounded by thick, angled walled fibres, as in palm stem. The term -closed bundle refers to the fact that there is no cambium between the -xylem and phloem, therefore the bundle is “closed” to further growth, -and not to the fact that it is frequently surrounded by fibres which -prevent further growth. In podophyllum stem (Plate 126) the xylem -portion of the bundle faces the centre of the stem and the phloem -portion of the bundle faces the epidermis. The xylem and phloem are -separated by a cambium layer, and both are surrounded by thick-walled -angled fibres which are the chief mechanical cells of the stem. This -bundle is, in fact, mechanically closed, but not physiologically -because a cambium is present. - -[Illustration: PLATE 126 - - CROSS-SECTION OF A CLOSED COLLATERAL BUNDLE OF MANDRAKE STEM - (_Podophyllum peltatum_, L.) - - 1. Vessels. - 2. Sieve cells. - 3. Cambium. - 4. Fibres. - 5. Parenchyma. - 6. Intercellular space.] - -[Illustration: PLATE 127 - - BI-COLLATERAL BUNDLE OF PUMPKIN STEM (_Curcurbita pepo_, L.) - - 1. Vessels. - 2. Sieve tubes.] - - - BI-COLLATERAL VASCULAR BUNDLES - -In the bi-collateral vascular bundle (Plate 127) the xylem is in -between two groups of phloem--namely, an inner group and an outer -group. - -In pumpkin stem a bundle occurs in each angle of the stem. The entire -bundle is surrounded by parenchyma cells. - -In an individual bundle the xylem consists of large circular vessels -and a phloem containing large sieve cells, many of which show the -yellow porous sieve plates. - - - OPEN COLLATERAL VASCULAR BUNDLES - -In the open collateral bundle (Plate 100) the xylem and phloem are -separated by the cambium layer, which, through its divisions, causes -the stem to increase in thickness each year. This type of bundle is -characteristic of the stems and roots of dicotyledonous plants. - -The bi-collateral bundle occurs in many leaves. The xylem in such -cases is central, the phloem strands occupying upper and lower -peripheral positions. - - - - - INDEX - - - Abbé condenser, illustration, 11 - - Absorption tissue, introduction, 121 - tissue of leaves, 125 - - Aerating tissue, introduction, 151 - - Annular vessels, illustration of, 129 - - - Bark, of white pine powdered, description of, 250 - of white pine powdered, illustration of, 251 - unrossed white pine, cross-section, illustration of, 249 - - Barks, description of, 248 - diagnostic structures of, 253 - structural variations of, 252 - - Base sledge microtome, 35 - sledge microtome, illustration, 35 - - Bast fibres, 89 - branched, 92 - branched, illustrations, 95 - crystal bearing, 90, 92 - description of, 100 - groups of, illustrations, 102 - non-porous and non-striated, 96 - non-porous and non-striated, illustrations, 101 - non-porous and striated, 96 - occurrence in powdered drugs, 103 - of barks, illustrations, 91, 93, 94 - of klip buchu leaf, 262 - of ruellia rhizome, 226 - of ruellia root, 223 - of ruellia stem, 235 - of spigelia stem, 235 - porous and non-striated, illustrations, 98 - porous and striated, 92 - porous and striated, illustrations, 97 - storage function of, 179 - striated and non-porous, illustrations of, 99 - - Bi-collateral vascular bundles, description of, 298 - - Buchu stems, cross-section, illustration of, 243 - cross-section, illustration of, 244 - powdered, description of, 245 - powdered, illustration of, 246 - - - Cambium of pink root, 221 - of ruellia rhizome, 226 - of ruellia stem, 237 - of spigelia rhizome, 223 - of spigelia stem, 235 - - Camera lucida, 22 - illustrations, 22 - - Care of microscope, 28 - - Celery fruit, diagrammatic drawing of, 287 - - Cell contents, 182 - aleurone grains, 197 - aleurone grains, description of, 198 - aleurone grains, form of, 197 - aleurone grains, structure of, 197 - aleurone grains, tests for, 198 - chlorophyll, 182 - crystals, 200 - crystals, composition of, 200 - crystals, micro-, 200 - crystals, raphides, 200 - crystals, rosette, 200 - crystals, solitary, variation of, 205 - cystoliths, 210 - cystoliths, forms of, 210 - cystoliths, occurrence of, 215 - cystoliths, tests for, 215 - hesperidin, 196 - hesperidin, test for, 196 - inulin, 194 - inulin, tests for, 194 - leucoplastids, 183 - mucilage, 194 - mucilage associated with raphides, tests for, 194 - mucilage, tests for, 194 - organic, 182 - starch grains, formation of, 183 - starch grains, hilum nature of, 188 - starch grains, hilum of, 185 - starch grains, mounting of, 188 - starch grains, occurrence of, 184 - starch grains, outline of, 185 - starch grains, size of, 185 - starch grains, tests for, 188 - tannin, 196 - tannin, occurrence of, 196 - tannin, test for, 197 - volatile oil, test for, 196 - volatile oils, 196 - - Cell division common to onion root, 56 - - Cell plate, 55 - - Cell sap, 53 - - Cell, typical, 53 - - Cell wall, 53 - - Chromatin, 54 - - Chromatin granules, 55 - - Chromatophores, 53 - - Chromosomes, 55 - - Closed collateral bundles of mandrake stem, cross-section - illustration of, 296 - - Collateral vascular bundles, 295 - - Collenchyma cells, composition of walls, 109 - illustrations, 108 - occurring in catnip and motherwort, illustrations, 107 - of ruellia stem, 235 - structure of, 106 - - Compound microscope, illustration, 10 - microscope, mechanical parts of, 7, 8 - microscope of Robert Hooke, illustration, 8 - microscope, optical parts of, 9, 11, 12 - microscopes, introduction, 7 - - Concentric vascular bundles, 295 - - Conducting tissue, introduction, 126 - - Cork cells, origin of, 88 - - Cortical parenchyma, conduction by, 147 - of ruellia stem, 235 - - Cortex, of pink root, 219 - of ruellia rhizome, 226 - of ruellia root, 221 - of ruellia stem, 235 - of spigelia rhizome, 223 - of spigelia stem, 233 - - Cover glasses, 43 - illustrations, 44 - - Crystal cavities, 176 - cells, storage function of, 179 - - Cutting sections, 31 - - Cystoliths, illustrations of, 214 - - Cytoplasm, 53 - - - Daisies, white, powdered, description of, 282 - illustration of, 283 - - Dissecting microscope, illustration, 5 - needles, 46 - needles, illustration, 46 - - Drawing apparatus, illustration, 23 - - - Ectoplast, 53 - - Embryo, diagnostic structures of, 291 - - Endocarp of celery fruit, 288 - - Endodermal cells, illustrations of longitudinal sections, 119 - illustrations of cross-sections, 117 - introduction, 116 - structure of, 116, 118 - - Endodermis, of klip buchu leaf, 262 - of pink root, 219 - of ruellia root, 223 - - Endosperm of celery fruit, 288 - of seeds, 291 - - Epicarp of celery fruit, 285 - - Epidermal cells of leaves, storage function of, 179 - - Epidermis, surface deposits of, 62 - of herbaceous stems, illustrations of, 152 - of klip buchu leaf, 260 - of leaves, illustrations of, 155 - of mountain laurel, 264 - of pink root, 219 - of ruellia rhizome, 226 - of ruellia root, 221 - of ruellia stem, 235 - of seeds, 289 - of spigelia rhizome, 223 - of spigelia stem, 233 - of testa, 63 - - Epidermis of trailing arbutus, 264 - - Equatorial plane, 55 - plate, 55 - - - Fibro-vascular bundles, composition of, 292 - of klip buchu leaf, 262 - types of, 292 - - Flowers, diagnostic structures of, 284 - parts of, 270 - - Folding magnifier, 4 - illustration, 4 - - Fruits, cellular structure of, 285 - diagnostic characteristics of, 288 - diagnostic structures of, 288 - - - Glandular hairs of peppermint, 178 - illustrations of, 165 - multicellular, 164 - multicellular, multiseriate stalked, 166 - multicellular, multiseriate stalked, description of, 166 - multicellular, multiseriate stalked, occurrence, 166 - multicellular sessile, 164 - multicellular stalked, 164 - multicellular, uniseriate stalked, 164 - stalked, illustrations of, 167 - storage function of, 178 - unicellular, 164 - unicellular, multiseriate stalked, 164 - unicellular sessile, 164 - unicellular stalked, 164 - unicellular, uniseriate stalked, 164 - - Glandular tissue, introduction, 164 - - Glass slides, 44 - illustrations, 44 - - Greenough binocular microscope, 15 - illustration, 15 - - Guard cells, 151 - - - Hairs, multicellular, multicellular non-branched, illustration, 75 - multicellular, multiseriate branched, of Shepherdia, 78 - multicellular, multiseriate branched, 77, 82 - multicellular, multiseriate branched, illustrations, 79, 81 - multicellular, multiseriate non-branched, 74 - multicellular, uniseriate branched, illustration, 76 - multicellular, uniseriate non-branched, 72 - multicellular, uniseriate non-branched, illustrations of, 73 - - Hand cylinder microtome, illustration, 34 - microtome, 31 - microtome, illustration, 31 - table microtome, 34 - table microtome, illustration, 34 - - Horehound, powdered, description of, 237 - powdered, illustration of, 238 - spurious, powdered, description of, 237 - spurious, powdered, illustration of, 239 - - Hypoderm of seeds, 289 - - Hypodermal cells, of leaves, storage function of, 179 - illustrations, 120 - structure of, 118 - - Hypoderms, of klip buchu leaf, 260 - of ruellia root, 221 - - - Illumination for microscope, 26 - - Indirect cell division, 54, 55 - - Inner bark of white pine, 248 - epidermis of seeds, 291 - - Insect flower leaves, powdered, illustrations of, 268 - stems, description of, 241 - stems, powdered, illustration of, 240 - - Insect flowers, closed, powdered, illustration of, 279 - open, description of, 280 - open, powdered, illustration of, 281 - powdered, description of, 278 - - Intercellular spaces, 158 - illustrations of, 160, 161 - - Internal phloem, of spigelia stem, 235 - - Inulin, illustrations of, 195 - - - Karyokinesis, 54, 55 - - Klip buchu, cross-section, illustration of, 261 - powdered, description of, 262 - powdered, illustration of, 263 - - - Labeling, 47 - - Latex cavities, 176 - tube cavities, 176 - tubes, 142, 144 - tubes, illustration of, 145 - vessels, illustrations of, 146 - - Leaf epidermis, 59 - illustrations, 60, 61 - - Leaf parenchyma, conduction by, 150 - - Leaves, diagnostic structures of, 267 - stomata, 260 - - Lenticel, illustration of cross-section, 159 - - Lenticels, ærating function of, 157 - structure of, 158 - - Linin, 54 - - Long paraffin process, 29 - - - Machine microtomes, 32 - - Measuring cylinder, 40 - illustration, 40 - - Mechanical stage, 21 - stage, illustration, 22 - tissue, 89 - - Medullary ray, 139 - bundle, 139 - bundle in tangential-section of quassia wood, 258 - cell, 141 - cell, arrangement of, in the ray, 142 - cell, structure of, 142 - cells, in cross-section of quassia wood, 254 - cells, in radial-section of quassia wood, 258 - cells, in tangential-section of quassia wood, 258 - cells, of ruellia stem, 237 - - Medullary rays, illustration of cross-sections of, 143 - illustration of longitudinal section, 140 - in cross-section of quassia wood, 254 - in radial-section of quassia wood, 254 - of pink root, 221 - of ruellia rhizome, 227 - of ruellia root, 223 - of spigelia rhizome, 226 - of white pine bark, 250 - - Mesocarp of celery fruit, 285 - - Method of mounting specimens, 41 - - Micro-crystals, illustrations of, 201 - lamp, 27 - - Micrometer eye-pieces, 21 - illustrations, 20, 21 - - Microphotographic apparatus, 24 - illustration, 24 - - Microscope, how to use, 25 - - Microscopic measurements, 19 - - Microtome, care of, 36 - - Middle bark of white pine, 248 - lamella, 55 - layers of seeds, 291 - - Minor rotary microtome, 36 - illustration, 36 - - Mountain laurel, cross-section, illustration of, 265 - - Mucilage cavities, 172, 176 - - Multicellular hair, 72 - - - Nuclear membrane, 55 - spindle, 55 - - Nucleoli, 55 - - Nucleus, 53 - - - Objectives, illustrations, 11 - - Ocular micrometer, 19 - illustration, 19 - - Oil cavities, occurrence, 178 - of leaves, 178 - of seeds, 178 - unicellular, 172 - - Open collateral vascular bundles, description of, 298 - - Origin of multicellular plants, 57 - - Outer bark of white pine, 248 - - - Palisade parenchyma, conduction by, 150 - - Papillæ, 67 - illustrations of, 275 - of stigmas, illustrations of, 276, 277 - stigma, description of, 274 - - Paraffin, blocks, 31 - embedding oven, illustration, 30 - - Parenchyma, aquatic plant, 150 - cells of white pine, 248 - conduction by, 144 - cortical, illustrations of, 148 - of mountain laurel, 264 - of trailing arbutus, 264 - pith, illustrations of, 149 - - Pericycle of pink root, 221 - of ruellia root, 223 - - Periderm, 80 - cork, 80 - illustrations of, 86 - of cascara sagrada, illustrations, 84 - of white oak bark, illustration of, 87 - parenchyma and stone cells, 85 - stone cells, 85 - - Permanent mounts, 41 - - Pharmacognostic microscope, illustration, 12 - - Phloem, centric bundle of calamus, cross-section, illustration of, - 294 - of ruellia rhizome, 226 - of ruellia stem, 235 - of spigelia rhizome, 223 - of spigelia stem, 233 - - Phloem parenchyma, conduction by, 150 - of pink root, 221 - of ruellia rhizome, 226 - of ruellia root, 223 - of ruellia stem, 235 - of spigelia rhizome, 223 - of spigelia stem, 235 - - Photosynthetic tissue, 163 - - Pink root, description of, 227 - - Pith parenchyma, conduction by, 147 - of pink root, 221 - of ruellia rhizome, 227 - of ruellia root, 223 - of ruellia stem, 237 - of spigelia rhizome, 226 - of spigelia stem, 235 - - Pitted vessels, with bordered pores, illustration of, 135 - illustrations of, 134 - - Plant hairs, forms of, 67 - introduction, 66 - - Polar caps, 55 - - Polarization microscope, 16 - illustration, 16 - - Pollen grains, 270 - non-spiny-walled, description of, 273 - smooth-walled, illustrations of, 271 - spiny-walled, description of, 273 - spiny-walled, illustrations of, 272 - - Preparation of specimens for cutting, 28 - - Protoplast, 53 - - - Quassia wood, cross-section, illustration of, 255 - radial-section, illustration of, 257 - - - Radial vascular bundles, 292 - skunk cabbage root, cross-section, illustration of, 293 - - Raphides, illustrations of, 203 - - Reading glass, 4 - illustration, 4 - - Reagent set, illustration, 39 - - Reagents, list of, 38 - - Research microscope, 13 - illustration, 14 - - Reserve cellulose, illustrations of, 180-181 - - Reticulate vessels, illustrations of, 133 - - Root hairs, 121, 122, 125 - illustration of, 123 - illustration of fragments, 124 - - Roots and rhizomes, 219 - diagnostic structures of, 227 - - Rosette and solitary crystals, illustrations of, 213 - crystals, illustrations of, 204 - crystals, inclosed, illustrations of, 206 - - Ruellia ciliosa, Pursh., powdered, illustration of, 229 - ciliosa, Pursh., rhizome, cross-section, illustration of, 225 - ciliosa, Pursh., stem, cross-section, illustration of, 236 - root, description of, 227 - root, illustration of, 222 - - - Scalpels, 46 - illustration, 47 - - Scissors, 46 - illustration, 46 - - Sclariform vessels, illustrations of, 132 - - Seeds, parts of, 289 - - Secretion cavities, of celery fruit, 288 - description of, 176 - illustrations of, 169-171 - introduction, 166 - lysigenous, 168 - schizogenous, 168 - schizo-lysigenous, 168 - unicellular, 168 - - Secretion cells, of klip buchu leaf, 262 - of white pine, 248 - - Short paraffin process, 29 - - Sieve cells, of klip buchu leaf, 262 - of pink root, 221 - of ruellia rhizome, 226 - of ruellia root, 223 - of ruellia stem, 235 - of spigelia stem, 235 - - Sieve plate, 138 - illustration of, 137 - - Sieve tube, illustration of, 137 - tubes, introduction, 136 - tubes, structure, 136 - - Simple microscope, introduction, 3 - - Slide box, 48 - box, illustration, 48 - cabinet, 49 - cabinet, illustration of, 49 - forceps, 45 - forceps, illustrations, 45 - tray, 48 - tray, illustration, 48 - - Solitary crystals, illustrations of, 207-209, 211, 212 - unicellular hairs, 69 - - Special research microscope, 14 - illustration, 14 - - Specimens, preservation of, 48 - - Spermoderm, of celery fruit, 288 - of seeds, 289 - - Spigelia marylandica, powdered, illustration of, 228 - rhizome, cross-section, illustration of, 224 - root, cross-section, illustration of, 220 - stem, cross-section, illustration of, 234 - - Spindle fibres, 55 - - Spiral vessels, illustrations of, 129, 130 - - Spongy parenchyma of klip buchu, 260 - - Stage micrometer, 19 - illustration, 19 - - Staining dish, 40 - illustration, 40 - - Standardization of ocular micrometer, 19 - - Starch grains, illustrations of, 186, 187, 189-193 - - Steinheil lens, 5 - illustration, 5 - - Stems, diagnostic structures of, 233 - dicotyledonous, 233 - herbaceous, 233 - monocotyledonous, 233 - - Stomata, ærating function of, 151 - illustrations of cross-section, 156 - relation to surrounding cells, 154 - types of, 153 - - Stone cells, of ruellia root, 223 - branched, 109 - branched, illustrations of, 110 - description, in, 112 - introduction, 109 - occurrence, illustrations, 115 - porous and non-striated, 111 - porous and non-striated, illustrations of, 114 - porous and striated, 109 - porous and striated, illustrations of, 113 - storage function of, 178 - - Storage cavities, 176 - cavities, illustrations of, 177 - cells, 173 - cells, cortical parenchyma, 173 - cells, illustrations of, 174 - cells, pith parenchyma, 173 - cells, wood parenchyma, 173 - tissue, 173 - walls, description of, 179 - - Stored mucilage and resin, illustrations of, 175 - - Surrounding cells, arrangement of, 154 - - Synthetic tissue, introduction, 163 - - - Temporary mounts, 41 - - Testa cells, 65 - epidermal cells, illustrations, 64 - - Tracheids of pink root, 221 - - Trailing arbutus leaf, cross-section, illustration of, 266 - - Tripod magnifier, 4 - illustration, 4 - - Turntable, 46 - illustration, 47 - - - Under epidermis of klip buchu leaf, 262 - epidermis of mountain laurel, 264 - of trailing arbutus, 264 - hypodermis of klip buchu leaf, 262 - palisade parenchyma of klip buchu leaf, 262 - - Unicellular clustered hairs, 72 - clustered hairs, illustrations, 71 - non-glandular hairs, 69 - solitary branched hairs, 72 - solitary hairs, illustrations, 70 - - Upper palisade parenchyma of klip buchu leaf, 260 - palisade parenchyma of mountain laurel, 264 - - - Vacuoles, 53 - - Vascular bundles, arrangement of, 292 - occurrence of, 292 - - Vessels, annular, 127 - and tracheids, introduction, 126 - in cross-section of quassia wood, 254 - in radial-section of quassia wood, 254 - in tangential-section of quassia wood, 258 - of ruellia rhizome, 226 - of ruellia root, 223 - of ruellia stem, 237 - of spigelia rhizome, 226 - pitted, 131 - pitted with bordered pores, 131 - reticulate, 131 - sclariform, 128 - spiral, 127 - - - Water pores, aerating function of, 151 - - Watchmaker’s loupe, 4 - illustration, 4 - - Wood fibres, color of, 104 - illustrations, 105 - in cross-section of quassia wood, 254 - in radial-section of quassia wood, 258 - in tangential-section of quassia wood, 258 - introduction, 104 - structure of, 104 - - Wood parenchyma, conduction by, 150 - in cross-section of quassia wood, 254 - in radial-section of quassia wood, 258 - of pink root, 221 - of ruellia rhizome, 227 - of ruellia root, 223 - of ruellia stem, 237 - of spigelia rhizome, 226 - of spigelia stem, 235 - - Woods, description of, 254 - diagnostic structures of, 258 - - Woody stems, buchu stem, description of, 242 - mature buchu stem, 242 - - - Xylem, of pink root, 221 - of ruellia rhizome, 226 - of ruellia root, 223 - of ruellia stem, 237 - of spigelia rhizome, 226 - of spigelia stem, 235 - - - - - Transcriber’s Notes - - The Table of Illustrations at the beginning of the book was created - by the transcriber. - - Inconsistencies in hyphenation such as - “extra-ordinary”/“extraordinary” have been maintained. - - Minor punctuation and spelling errors have been silently corrected - and, except for those changes noted below, all misspellings in the - text, especially in dialogue, and inconsistent or archaic usage, - have been retained. - - Page 53: “The outer portion of the nucelus” changed to “The outer - portion of the nucleus”. - - Page 54: “the centre of the nucelus” changed to “the centre of the - nucleus”. - - Page 62: “typical forms of arrangement of epidermal calls” changed - to “typical forms of arrangement of epidermal cells”. - - Page 104: “of logwood and santalum rubum” changed to “of logwood - and santalum rubrum”. - - Page 107: “the cross-section of catnip stem (_Nepeta cateria_” - changed to “the cross-section of catnip stem (_Nepeta cataria_”. - - Page 120: “Cross-section sarsaparilla root (_Smilex officinalis_” - changed to “Cross-section sarsaparilla root (_Smilax officinalis_”. - - Page 150: “cells are the narrowest parenchyma cells occuring” - changed to “cells are the narrowest parenchyma cells occurring”. - - Page 155: “Upper epidermis of deer tongue (_Trilisia - odoratissima_” changed to “Upper epidermis of deer tongue - (_Trilisa odoratissima_”. - - Page 171: “Parenchyma cells with protuding” changed to “Parenchyma - cells with protruding”. - - Page 193: “grains of paradise (_Amomum meleguetta_” changed to - “grains of paradise (_Amomum melegueta_”. - - Page 237: “Marrubium perigrinum, which is a related species of - horehound” changed to “Marrubium peregrinum, which is a related - species of horehound”. - -*** END OF THE PROJECT GUTENBERG EBOOK HISTOLOGY OF MEDICINAL PLANTS *** - -Updated editions will replace the previous one--the old editions will -be renamed. - 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