Introduction

GIFT OF MICHAEL REESE BIOLOGY LIBRARY G A COURSE OF PRACTICAL INSTRUCTION IN BOTANY A COURSE OF PRACTICAL INSTRUCTION IX BOTANY BY F. O. BOWER, D.Sc, F.L.S. KEGIUS PROFESSOR OF BOTANY IN THE UNIVERSITY OF GLASGOW THIRD EDITION n to o n MACMILLAN AND CO. AND NEW YORK. 1891 The Right of Translation, and Reproduction is Reserved, BIOLOGY RA G RICHARD CLAY AND SONS, LIMITED, LONDON AND BUNGAV. Part I. First Edition printed 1885 ; Second Edition, 1888. Part II. First Edition printed 1887. Complete, made up from parts, 1888. Third Edition, 1891. PREFACE THIS Course of Practical Instruction in Botany having now passed through two editions, it will be unnecessary again to state the history of its origin ; this has been sufficiently set forth in the Preface to the earlier Editions. The book now stands for the first time as a connected whole, with continuous pagination: as compared with the previous editions of the two parts, hitherto separate, the present issue shows but slight changes, excepting as regards arrangement. The chapter on Micro- chemical Reactions (Chapter III,) has been greatly curtailed, and the specific reactions of the less common substances in the plant-body have been introduced in the text, at various points where such substances may be met with in the study of the types. In dealing with the Angiosperms the description of work to be done on the seed and fruit, and on germina- tion has been placed after that on the ovule and fertilisation ; this is its reasonable position. The VI PREFACE terminology of the tissues of the root has been revised in accordance with recent views. A chapter has been devoted to the Charaeese, which were entirely omitted in previous editions various ; subsidiary types have been introduced here and there in the text in small print, with a view to extending the course beyond the dangerously narrow limits of pure type-teaching. These and other alterations have been made in response to the remarks and suggestions of critics and friends, to whom I take this opportunity of expressing my obligation. GLASGOW, April 1891. F. O. BOWER. TABLE OF CONTENTS PAOE LIST OF APPARATUS 1 INTRODUCTORY CHAPTERS. M A. ( Making Preparations 4 B. ( Adjustment of the Microscope 17 II. Practical Exercises involving Simple Methods . 24 III. Common Micro-Chemical Reactions 35 Vlll CONTENTS PRACTICAL DIRECTIONS FOR THE STUDY OF TYPES PHANEROGAMS. I. ANG 10 SPERMS. t VEGETATIVE ORGANS. A. DICOTYLEDONS. T YPE. Mature ............. 55 Young .............. 76 Apical Bud ............ 79 Node .............. 86 ARBOREOUS TYPE ........ 88 AQUATIC TYPE ......... 110 Sieve Tubes ........... 113 ........ Laticiferous Tissues 118 LEAF Bifacial Type. Petiole ............... 122 Lamina ............. 124 .......... Isobilateral Type 134 Centric Type ............ 136 Aquatic Type ........... 188 LEAF-SCARS, AND FALL OF LEAF ...... 143 HAIRS AND EMERGENCES ......... 145 ROOT Herbaceous Type .......... 148 Ligneous Type .......... . 153 Apex ................ 157 B. MONOCOTYLEDONS. STEM HERBACEOUS TYPE ...... 161 BULBOUS TYPE ......... 167 ARBOREOUS TYPE ........ 169 AQUATIC TYPE ......... 171 LEAF Bifacial Type ........... 172 .......... Isobilateral Type 179 Aquatic Type ............ 180 CONTENTS PHANEROGAMS (continued). ROOT APEX AERIAL ROOTS ix PAGE 180 183 185 t t REPRODUCTIVE ORGANS. OBSERVATIONS WITH THE NAKED EYE . . . 187 DEVELOPMENT OF THE FLOWER 194 CALYX AND COROLLA 197 THE STAMEN 200 CARPEL AND OVULES 204 FERTILIZATION 206 DEVELOPMENT OF THE EMBRYO. Dicotyledon 209 Monocotyledon 211 DEVELOPMENT OF ENDOSPERM 212 MATURE SEED AND EMBRYO. Dicotyledons 215 Monocotyledons 218 RESERVE AND TRANSITORY MATERIALS IN SEEDS, TUBERS, &c 220 GERMINATION. Dicotyledons 225 Monocotyledons 227 II. GYMNOSPERMS. t VEGETATIVE ORGANS STEM LEAF ROOT t t REPRODUCTIVE ORGANS RIPE SEED AND GERMINATION . 229 232 244 247 252 . 258 PTEKIDOPHYTA. A. LYCOPODINEJE. I. SELAGINEL.LA (Heterosporous Type). SPOROPHYTE 261 OOPHYTE X CONTENTS PTERIDOPHYTA (continued). II. LYCOPODIUM (Homosporous Type). PACK SPOROPHYTE 275 B. FILICINE.E. I. ASPIDIUM (Homosporous Type). MATURE SPOROPHYTE. EXTERNAL CHARACTERS 287 ANATOMICAL CHARACTERS TO BE OBSEKVED WITH THE NAKED EYE 289 MICROSCOPIC OBSERVATIONS Stem 292 Root 303 Leaf 307 Sporangia 309 OOPHYTE 311 YOUNG SPOROPHYTE 317 II. FIXiTTIiARIA (Heterosporous Type) 319 C. EQUISETINE.E. EQUISETUM. SPOROPHYTE 325 OOPHYTE 340 BRYOPHYTA. A.MUSCI. POLYTRICHUM. GENERAL EXTERNAL CHARACTERS MICROSCOPIC INVESTIGATION OOPHYTE SPOROPHYTE SPHAGNUM B. HEPATIC^. MARCHANTIA. GENERAL EXTERNAL CHARACTERS MICROSCOPIC OBSERVATIONS SPOROPHYTE . 341 342 350 357 360 363 .376 CONTENTS THALLOPHYTA. A. ALG^E. FLOKIDE^l. POLYSIPHONIA PH/EOPHYCE.E. FUCUS LAMINARIA CHARACE^E CONFERVOIDE.E. COLEOCH^TE JEDOGONIUM UIiOTHRIX CLADOPHORA SIPHONED. VAUCHERIA VOLVOCINEJ3. VOLVOX PLEUROCOCCUS HYDRODICTYON CONJUGATE. SPIROGYRA DESMIDS DIATOMS CYANOPHYCE^:. NOSTOC OSCIIiIiATORIA GL-ffiOCAPSA B. FUNGI. BASIDIOMYCETES. AGARICUS ^CIDIOMYCETES. PUCCINIA xi PAGE 379 391 406 409 419 421 424 427 429 437 439 441 442 447 449 451 452 452 453 . . 462 Xll CONTENTS THALLOPHYTA (continued}. A8COMYCETES. PEZIZA PARMELIA CLAVICEPS EUROTIUM PERONOSPORE^. PYTHIUM CYSTOPUS MUCORINE^E. MUCOR SPORODINIA PAGR 470 473 481 484 491 495 497 . 500 APPENDIX A. List of Reagents, their Preparation, and Uses . . 503 APPENDIX B. List of the Reactions of Bodies commonly found composing the Tissues of Plants 518 APPENDIX C. List of the Specimens mentioned in the Book : the sourcesfrom which they may be obtained, and their preparation 523 INDEX . 537 PEACTICAL BOTANY The following is a list of apparatus required for ordinary work in the botanical laboratory. The articles marked with an asterisk (*) are absolutely essential to successful work A 1. pair of fine scissors with sharp points. 2. Fine-pointed forceps. *3. One or more good razors (see p. 8), and a strop and bone for sharpening them. 4. Scalpels of various sizes : a fine eye-scalpel with a long narrow blade will be found to be very useful. A 5. section-lifter. *6. Mounted needles. 7. Several fine camels'-hair brushes. *3. Watch-glasses of various sizes, flattened at the middle of the convex side so as to stand steadily. *9. Glass or porcelain ointment pots, with lids. 10. Test-tubes and beakers. A 11. spirit-lamp. A 12. black enamelled tile for mounting on. *13. Glass slides, with ground edges (3 in. x 1 in.). *14. Tbin cover-glasses, square, or circular (f in. diameter). *15. Blotting-paper, cut or torn into small pieces. PRACTICAL BOTANY *16. Drawing-paper or card, with a hard smooth surface, or a note-book of such paper, without lines. *17. Hard pencils (H. or H.H.H.) and india-rubber. *18. Gummed labels (1 in. x f in.) for naming slides. A *19. coarse duster, and a finer cloth, e.g. an old pocket- handkerchief. A 20. rack for keeping slides temporarily, and a bell-glass to cover it. A *2l. simple lens. *22. A compound microscope. This should be one of the smaller stands with a short tube, e.g. Hartnack No. III. A, or Zeiss No. V., VI., or VII. : similar stands of varying merit are to be obtained from most of the English makers. The microscope should be provided with *i. High and low eye-pieces : the longer is the lower power, the shorter the higher. *ii. Two objectives, the lower power (Zeiss A, or Hartnack No. 3) of about 1 inch focal length. The higher (Zeiss D, or Hartnack No. 7) about one-sixth inch or one-eighth inch focal length. A *iii. micrometer, either adapted to the eye-piece, or a stage micrometer. A iv. nose-piece to carry two, or, if necessary, more objec- tives : its use will save much time, v. A camera lucida for drawing, vi. An erecting eye-piece is also a useful adjunct, when dissection is to be carried on under the microscope. A *23. rack or tray to hold small glass-stoppered bottles con- taining reagents : the following are the reagents which are in most constant use Weak *a. glycerine, i.e. Price's pure glycerine diluted with an equal volume of distilled water. *b. Caustic potash: make a 2 per cent, solution of the solid sticks of caustic potash in distilled water, and filter. *c. Acetic acid : one volume of glacial acetic acid is to be diluted with 99 volumes of distilled water. *d. Iodine solution : this may be obtained by diluting the APPARATUS 3 liquor iodi of the Pharmacopoeia ; or as follows : dissolve a small quantity of potassium iodide in distilled water, and add crystals of iodine : if the solution be too deeply coloured it may be diluted with distilled water to the colour of brown sherry. *e. Chlor-zinc-iodine (Schulze's solution) may be pur- chased ready prepared from the dealers in micro- chemical reagents : or it may be prepared as follows : (1) Dissolve 110 grms. of zinc in 300 c.c. of pur hydrochloric acid, and evaporate to 150 c.c. (sp. gr. about 1-8). (2) Dissolve 12 grms. of KI in as little water as possible : add 0'15 grm. of iodine. (3) Mix (1) and (2), and filter, if necessary, through asbestos. The solution should have a dark sherry-brown colour. */. Solution of aniline chloride : a saturated solution is made in distilled water, filtered, and a few drops of hydrochloric acid added so that it may give a distinctly acid reaction. The solution should be colour- less. A *g. solution of common salt : a 5 per cent, solution, i.e. 5 grins, of salt to 100 c.c. distilled water. Many other reagents besides these will be required for the work described below : also substances for permanent mounting and sealing up of slides : their preparation and uses are detailed in the Appendix A. Care should be taken in the preparation of the reagents : they must be kept pure, and should be renewed occasionally. Glass rods with rounded ends are to be used for removing drops of the reagents from the bottles to the slide, and the rod should always be cleaned before dipping it into a reagent-bottle. 24. Two wash-bottles such as are in ordinary use in a chemical laboratory : the one should contain alcohol (methyl- ated), the other distilled, water. B2 t A. Making Preparations I. Preservation of Material, In many cases it is possible, and even preferable, to use fresh material, but it is often convenient to keep it for a time, since many of the specimens required are only to be obtained at certain seasons of the year : the best liquid for this purpose is ordinary methylated alcohol, in such quantity as completely to cover the material. It must be remembered that this will extract the green colouring matter (chlorophyll) from the material immersed in it, as well as resin and other substances. II. Hardening.. It is not necessary, for the general study of the histology of the mature parts of plants, to harden them, for the tissues are usually sufficiently firm to admit of their being cut satisfactorily. In the case of young, or of exclusively parenchymatous tissues especially those of non-vascular plants, it is necessary, to harden them, and for this purpose alcohol may be used. When it is desired to study the structure of the protoplasm, and of the nucleus, special methods must be employed for hardening them, or rather for fixing MAKING PREPARATIONS 5 them as nearly as possible in the condition in which they are during life. For this purpose one or other of the fluids mentioned below may be used. Care must be taken that the objects shall be of small size, that the quantity of hardening fluid is large relatively to the bulk of the object, and that the fluid has ready access to all parts of it. Large objects should be cut up into pieces of moderate size, so that the reagent may readily gain access to all parts of the tissue. The following are the best fluids for this purpose : 1. Absolute alcohol or methylated spirit. 2. Picric acid (saturated solution in water). 3. Chromic acid (O'l 05 per cent, solution in water). 4. Osmic acid (1 1 per cent, solution in water). These reagents are only to be applied to fresh material. When absolute alcohol is used, the object may be kept in it for an indefinite period. Such treatment generally makes the object brittle ; this may be remedied when the object is to be mounted in glycerine by placing it, for at least twenty-four hours before it is to be cut, in a mixture of glycerine and absolute alcohol in equal parts, leaving it exposed to the air so that the alcohol may gradually evaporate. The glycerine slowly saturates the object and restores its toughness. This can only be done when the sections are to be mounted in glycerine. When picric or chromic acid is used, the object should be immersed in it until each part of it is thoroughly permeated by the reagent ; the length of time required for this varies with different material, and in the case 6 PRACTICAL BOTANY of chromic acid, with the strength of the solution used, from a few minutes to twenty-four hours or more. The objects must then be washed thoroughly with water : they are then to be placed in dilute methylated spirit (50 per cent.), subsequently in stronger spirit (70 per cent.), and finally in absolute alcohol or strong methylated spirit, which must be changed so long as any colour is still extracted from the objects. They may be preserved in this for future use. When osmic acid is used, the fixing effect is pro- duced much more rapidly ; in the case of simple structures, such as unicellular or filamentous Algge, a few minutes (515) generally suffices; in the case of more complex structures, such as ovules, sporangia growing points, &c., the object may be left in the acid till it looks black on the exterior : it must be then well washed with dilute alcohol (50 per cent.), and left in it for some time, and be then removed to 70 per cent. The sections are best mounted in dilute glycerine. In some cases osmic acid produces an excessive blackening of the cells, which can be removed by treatment with chlorine- water. Of the hardening reagents above mentioned absolute alcohol, methylated spirit, and picric or chromic acids are those most generally used. The following is a useful method for preparing sea-weeds : to a quantity of saturated solution of picric acid in sea-water add three or four times its volume of sea-water, and treat the tissue with it for ^ hr. to 2 hrs. : wash well with sea-water so as to remove the picric acid, and then treat successively with 30, 50, 70, and 90 per cent, alcohol. It is advisable in cases in which the cell-walls tend to swell up CUTTING SECTIONS 7 excessively (as in many Algse) to use solutions of picric, chromic, or osmic acids, to which an equal volume of absolute alcohol has been added. III. Cutting Sections. In order to investigate the structure of the tissues of a plant or member, it is usually necessary to cut sections, i.e. thin slices, in various directions. To make a complete study of a solid mass of tissue, sections must be cut in three different planes at right angles to one another. Taking the case of a cylindrical stem, the best way to study its structure would be to cut (i.) Transverse sections, in planes at right angles to the organic axis. (ii.) Radial longitudinal sections, in longitudinal planes including the organic axis. (iii.) Tangential longitudinal sections, in longitudinal planes which do not include the organic axis. This may be illustrated by a diagram (Fig. 1), which may be taken to represent the transversely cut end of a cylindrical stern, the tissues being arranged with reference to a central point (E) : transverse sections are those which are in transverse planes, parallel to the plane of the paper in Fig. 1. The line including the central points of successive imaginary transverse sections is the organic axis. Radial and tangential sections are both in planes vertical to that of the paper in Fig. 1 : a radial section (A E B) includes the organic axis (E), and a slice of tissue thus cut when examined from a direction indi- cated by either of the arrows (x) will show in surface view those cell-walls which run radially : a tangential section (c D) does not include the organic axis (E), and 8 PRACTICAL BOTANY such sections when examined from a direction indicated by the arrows (y y) will show the tangential walls in surface view, while the radial walls, previously seen in surface view would present their cut edges to the observer. In the case of tangential sections only the central part of the section (i.e. the part near to y y) is to be examined, for obviously in the more lateral parts of the section (c D) the radial lines are cut not vertically but obliquely. In all cases the sections must be cut accurately in the plane intended : if the sections be cut obliquely the difficulty of understanding the structure will in almost every case be enormously increased. A razor of good quality is the best cutting instru- ment : there is some variety of opinion as to the best form of blade ; some prefer a hollow-ground razor, which, though well suited for cutting small sections, will not CUTTING SECTIONS 9 serve for sections of large area ; for this work a razor with one flat side is recommended. For general use, not only in cutting small objects and soft tissues, but for the e very-day work of the laboratory, an ordinary, very slightly hollow-ground razor, of good quality will be found the most useful. The razor should be stropped to a smooth edge, and the blade should be carefully protected when not in use : it should never be left open on the work-table, and the blade should always be cleaned after use, since the acid juices of plants are apt to corrode it. It will be found convenient to have a glass of water (or weak spirit when resinous tissues are being cut) on the work-table, into which the blade of the razor may be plunged at once after use ; this will prevent immediate corrosion. The success of work in the laboratory depends very greatly on due care in the direction of section, and on the condition of the edge of the razor. Almost all the sections required in the succeeding pages of this book can be made by hand : elementary students are advised to avoid the use of a microtome, which is for their work a useless and expensive incumbrance ; they should rather cultivate that small amount of manual dexterity which will suffice for the successful preparation of almost all the objects to be described below. When however a series of successive sections of an object is required, a microtome may be used, care being taken to keep the sections in their proper order, and the right way up. For advanced students a microtome may be found a convenience, though it is not actually necessary for any of the work detailed in this book. Tins being so, no description will be given 10 PRACTICAL BOTANY of the special methods of preparation of objects for cutting by the microtome, nor of the different forms of microtome, or the way in which the microtome is to be used. When cutting sections the razor is to be opened so that the blade is in a line with the handle : the object to be cut may be held in the thumb and first finger of the left hand, while the razor is grasped firmly by the four fingers of the right : it may be found convenient to rest the thumb of the right hand on that of the left so as to regulate the movements of the right hand. The edge of the razor is not to be rudely forced through the tissues of the specimen, but a sliding cut is to be made, thus using a considerable length of the edge of the razor : in this way a smoother surface of section is obtained, and the tissues are not displaced as they otherwise might be. Care must be taken to keep the object and the razor wet during the process of cutting, in order to avoid the entrance of air into the tissue, and to prevent adhesion of the section to the razor. When fresh material is cut, water or very dilute alcohol may be used for this purpose, but if material which has been hardened is cut, it is advisable to use alcohol of the same strength as that in which the material has been preserved. IV. Embedding. The objects are frequently so large that they may be held in the hand whilst they are being cut. If they are too small for this, it is con- venient to embed them in some substance. The simplest method is to fix the object into a slit in a piece of pith. Dried elder-pith is the best, and it may be bought ready prepared from the dealers. When the sections are to be made with a microtome EMBEDDING 11 or when the object to be cut is small, or easily damaged, it is more convenient to embed in some easily fusible substance : by this means also the form of the object is less likely to be distorted in the process of cutting. Various substances, or mixtures of substances, are used for this purpose, of which the following is perhaps the best : Solid paraffin (melting-point about 58 C.) : 2 parts. Vaseline : 1 part. These must be melted together and well stirred. The resulting substance is -sufficiently transparent to enable the exact position of the object to be ascertained ; it is easy to cut, and it is readily soluble in carbolic acid and turpentine. The relative proportions of paraffin and vaseline may be varied somewhat to suit the object ; a softer mixture is produced by increasing the pro- portion of vaseline. Samples of paraffin which vary in hardness and melting point may be obtained from the dealers, the softer paraffin with low melting point will be the most useful. The ordinary method of embedding is to make a cavity in a piece of the substance sufficiently large to contain the object, which, if fresh, must have been previously washed with alcohol to remove all traces of water from its surface. If the object had been previously preserved in alcohol, all superfluous fluid must be removed from the surface with blotting-paper, but care must be taken that the spirit which permeates the tissue shall not evaporate. The object is then placed in the cavity, and without unnecessary delay a small quantity of the embedding substance, melted over a 12 PRACTICAL BOTANY spirit-lamp in a small tinned iron spoon, is poured into the cavity so as to surround and cover the object. If the object be small it will be found convenient to heat one end of a thick copper or platinum wire, and with it melt a small cavity, in which the object may be placed in such position as is found convenient. The sections must not be made until the paraffin is quite cold, and firmly set. It is important to keep the embedded objects wet with alcohol during the process of cutting, in order to prevent the drying-up of the object, and its consequent contraction away from the substance in which it is embedded. Another method of embedding is to moisten the object in water, and then suspend it by means of a thread in some white of egg, which has been previously well shaken up, and then strained through muslin. The white of egg should be in an evaporating dish. The object should be left thus suspended for some hours, so that the white of egg may come into close contact with all parts of it. Heat is then applied by means of a waterbath, and the white of egg coagulates. The part surrounding the object is now cut out and hardened in alcohol for some days. This method is useful