Handbook of practical botany : for the botanical laboratory and private student

Front matter

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Preface To The English Edition

Although the last two or three years have produced at least as many works on Practical Botany for Laboratory purposes, no apology is needed for reproducing from the German one which has no counterpart in the English language, and which has the advantage of being written by one of the greatest living masters of microscopical observation.

Although Professor Strasburger has revolutionized the science of Botany in more than one direction, no work of his has as yet come before an English public in its own tongue; but it is perhaps not unfitting that the Author’s first introduction to the English-reading student should be in the role of teacher of those arts of manipulation and observation by the exercise of which his own fame has been gained.

This edition has the advantage of revision and of numerous additional notes by the Author ; some portions have been well-nigh rewritten. To these I have ventured to add notes of my own, intended to either simplify or amplify the description, or to enable the material selected by the Author to be replaced by some other, probably more readily obtainable. These additions have been either inserted as footnotes, or, where intercalated in the text, are usually inserted between square brackets [ ] . The Introduction I have, with the consent of the Author, nearly rewritten, in order to make it more suited to the English student ; similarly with a few other isolated paragraphs. A few additional illustrations I have been enabled to add, through the courtesy of the Publishers; descriptions of, and references to, these are likewise enclosed in brackets. To make the book more conveuient in use, I

VI

PREFACE TO THE ENGLISH EDITION.

have given at the head of each chapter (task, or lesson, in the original) a list of the objects required for study in that chapter. I regret that I did not add to these lists any special reagents which might be required for use ; possibly a future edition may give opportunity for this.

I have considerably enlarged the scope of Appendices II. and III., and have added two new Appendices, I. and IV., which I hope may be useful to the student. Throughout the work I have likewise added the common English names (if any) of the plants referred to.

The student will probably not be able to carry out all the investigations constituting a chapter at the same time. A careful note should be made of any which are thus postponed, so that they may be taken up in due season. It is not unlikely that some may not come at all within the range of the student’s observation ; for these examples the book must be looked upon in the light of a text-book.

The student is earnestly urged to study from the beginning the Author’s methods of work. These are especially noteworthy when he comes, perhaps incidentally, to correlate structure with function. The interdependence of these two factors in the plant’s life history is the great underlying principle of modern botanical teaching, and the student cannot too soon begin to exercise his thoughts in this direction, resting assured that his methods are right even though his results may for the time being prove to be erroneous.

As to translation, no one can feel so fully as myself its many and serious defects. I can only plead that the work was executed at a time of serious pressure, and, although circumstances have delayed the issue of the book, the manuscript was out of my hands, and therefore only subject to such limited correction as proof-sheets would allow.

w. n.

Birmingham, Sepiemhcr, 1880.

Preface

TO THE

SECOND ENGLISH EDITION.

Although anything like a complete revision of the text has been impracticable, I have been enabled, through the liberality of the Publishers, to make several considerable and important additions both to the text and figures (mainly derived from the Second Edition of the Botanisches PracUcum), and the chapters upon “ Vascular Bundles ” and “ Bacteria ” have been to some extent re-written. A list of the most important of these changes will be found on page xii., at the end of the Contents. I hope that these additions will still further enhance the utility of the work to those for whom it is intended. I have likewise made a few verbal and other corrections, and, after much hesitation, have eliminated the square brackets wherever this has been feasible.

I have most heartily to thank many correspondents here, in America, and elsewhere, for numerous notes, memoranda, and criticisms. Although I may not at present have been able to make use of them, these suggestions will not be lost sight of; and even should they never be used, I am none the less grateful for the kindly spirit which has prompted their transmission.

W. II.

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I

Contents

Introduction. Instruments, Apparatus, Keagents, Materials . •

PAGB

xiii

Introduction

lower price, and, like the cheaper English makers hereafter noted, have brought out instruments suited for general use under the name either of “ Student’s,” “ Educational,” or “ Economic ” microscopes. Of such kind we will specially indicate a few.* These will be exclusively monocular ; binocular microscopes are in no way needed.

Ross & Co. (112, l^ew Bond Street, London) produce an instrument of high quality and comparatively low price, called the “ Student’s Microscope,” with rotating glass stage, coarse and fine adjustment by screws, and a “ swinging tail-piece for oblique illumination,” originally devised by Zentmayer, of Philadelphia, into which may be fixed various substage appliances, such as condenser, etc. Price, with one eye-piece (A), and in mahogany case, £10 10s. Another cheaper stand is the “ Student’s Monocular Stand, Ro. 1,” with coarse adjustment by sliding the tube, and fine adjustment by a screw, circular rotating glass stage, and draw-tube into which the continental eye-pieces will fit. (This is the case also with the above higher-priced instrument.) With one eye-piece the price of this stand is £4 IO5.; a diaphragm to the stage costs 8s., and a case for the microscope 11s. extra. Ross’s best objectives are too expensive for ordinary student use ; he offers some for the above microscope — e.g. 1 inch of 15° angular aj^erture at £1 5s., and 1 of 75° for £2 2s. ; or, together with the stand, as above, £8 16s., to which ought to be added a second eye-piece, which costs £1. For 15s. extra this microscope can be obtained with screw coarse adjustment. Instead of these objectives, the stand as above can be fitted with objectives by other makers. f

R. & J. Beck (68, Cornhill, London, E.C.) offer a useful instrument under the name of the “ Monocular Economic Microscope ” (No. 24, Catalogue 1885), having coarse adjustment by sliding tube, fine do. by screw, drawtube, 1 eyepiece, diaphragm.

* For further information and particulars the reader is referred to any of the current works on the microscope, such as those of Dr. Lionel Beale, Dr. Jabez Hogg, and, especially, that of the late Dr. Carpenter.

t It is here perhaps desirable to note that all English objectives are made with the same size screw, the “ Microscopical Society’s Screw,” known abroad as the “ English Screw,” and therefore will fit any English instrument. Foreign objectives, if instructions are given to that effect, are likewise made with this screw, usually with an extra charge of but a shilling or two, sometimes none. Foreign microscopes can be made with the same gauge, or provided Avith adaptors. It is not improbable, and greatly desirable, that the English, or some other standard, screw may become universal, as the confusion amongst foreign makers is extreme. At the same time all of, at least, the smaller English microscopes would be better made for eye -pieces of continental sizej

INTRODUCTION. ^

1 inch and j inch Object glasses, in mahogany case, for £5 5^. Without objectives, but with 2 eye-j)ieces, £3 10s. To this can be fitted an achromatic condenser for £1 2s., and other pieces of apparatus. Beck’s best objectives are expensive; but he constructs good student glasses at a lower rate.

Amongst the cheaper optical firms, we may mention the following : —

C. Baker (241 & 245, High Holbom, London, W.C.) publishes a “ Medical Microscope ” on the old continental model (of Hachet & Hartnack), with draw-tube, coarse adjustment by sliding tube, fine by screw, and 2 eye-pieces, in mahogany case, for £3 3s. With 1 inch and ^ inch object-glasses and condenser for opaque objects, £6 7s.

Chas. Collins (157, Gt. Portland Street, Oxford Street, London, W.) offers a “Histological Microscope,” with coarse adjustment by rackwork or by sliding tube, fine screw adjustment, one eyepiece, 1 inch and \ or \ objectives, in mahogany case, for £5 10s.; or with extra eye-piece, polariscope and stage condenser, for £7 10s. Also a “ Student’s Microscope ” of rather larger size, with similar fittings, at an extra cost of £1 10s.

H. Crouch (66, Barbican, London, E.C.) publishes “ The Histologist’s Microscope,” coarse adjustment by sliding in cloth-lined tube, fine by screw, glass stage with diaphragm, 1 inch and

or inch objectives and 2 eye-pieces, in mahogany case, for £5 5s. A Stand Condenser can be added for 8s. OcZ., and an Achromatic Condenser for £1 Is.

T. Darton & Co. (45, St. John’s Street, West Smithfield, London, E.C.) have an “Improved Histological Microscope,” on much the same model as that of Crouch, with di*aw-tube, screw fine adjustment, 2 eye-jheces, inch and ^ inch objectives, glass stage, in mahogany cabinet, for £5 5s. Other apparatus can be fitted.

Parkes & Son (St. Mary’s Row, Birmingham) offer a “ Portable Educational Microscope,” a reliable and very steady instrument, with coarse adjustment by body sliding in cloth-lined tube, fine by screw, draw-tube, 2 eye-pieces, 1 inch objective, separating to 2 inches, ^ inch ditto, with magnifying power ranging, with use of draw-tube, from 140 to 470 diametei'S ; also with spot lens, condenser on jointed arm attached to the stand, diaphragm, with disc for “ white-cloud illumination,” and glass stage, in mahogany case with leather handle, £6 10s. If with inch objective instead

XVI

INTKODUCTION.

of j, increasing magnifying power to 560 diameters, 5s. extra; or, instead, with inch, magnifying np to 700 diameters, £7. The object-glasses are provided with a “ patent sliding adapter,” obviating the necessity for screwing in exchanging one glass fov another while at work. A screw nozzle can also be had to adapt it for all other objectives with the English screw. An achromatic condenser can be supplied adapted for it.

PiLLisCHER (New Bond Street, London), under the name of “ International Microscope,” offers a stand on the old continental model, but with rackwork coarse adjustment, 2 eye-pieces, -f and -f inch objectives, giving, with draw-tube, a range of from 50 to 420 diameters, in case, for £7 lOs,

Swift & Son (81, Tottenham Court Road), under the name of the “ College Microscope, No. 1,” offer an instrument with coarse adjustment by sliding in cloth-lined tube, fine by screw, draw-tube (too large for continental eye-pieces), diaphragm, 1 eye-piece, 1 inch and j inch objectives, in case, for £5 5s. The same with screw coarse adjustment, glass stage, and jointed mirror, £1 10s. extra. Achromatic condenser, 12s. to £1 5s.

Other instruments of equal excellence with the above are doubtless manufactured ; there is no pretence that this list is complete, nor is any comparison intended to be instituted.

German Makers. Of these, the following two makers may he considered typical : —

Carl Zeiss (Jena). Stand VIIa, with 3 eye-pieces. Nos. 2, 4, and 5, and objectives B and D, price £7 13s. This stand has an unjointed back, sliding tube for coarse and screw for fine adjustment, and swinging mirror. The instrument gives a magnification from 95 to 580 diameters. The glasses of Zeiss are unsurpassed.

E. Leitz (Wetzlar). A stand of similar model to that of Zeiss, with eye-pieces i, and iii, and objectives 3 and 7 (No. 17 in catalogue of 1882), and magnifying from 80 to 500 diameters, price £5 IO5. The objectives of Leitz are low in price, but remarkably good.

French Makers. The two following are probably the best : —

Bezu, Hausser & Co. (Paris, Rue Bonaparte, 1, successors to the old house of Prazmowski, formerly Hartnack & Prazmowski), Stand VIII., eye-pieces 2 and 4, objectives 4 and 8, magnifying l^JTRODUOTION. XVll.

50 to 600 diameters, price about £8. Stand VIIIa, the same as above, but with jointed back, 12.5. extra,

C. Verick* (Paris, Rue de la Parcheminerie, 2).. Stand VI., with jointed back, with diaphragm disk and draw- tube, 2 eje-pieces, 1 and 3, 2 objectives, 2 and 6, magnifying 60 to 500 diameters, price 165 - francs (about £6 125.) ; or Stand IV., with which achromatic condenser and polariscope can be used, about £2 more. These two instruments are now very widely used in Prance.

Most, or all, of the above makers, English and foreign, manufacture microscope stands of cheaper quality than the above ; it must, however, be borne in mind that accurate observation needs an instrument which is capable of it, and while there is, and ought to be, every desire to keep the cost within a reasonably small sum, true economy does not consist in purchasing an instrument which may be a constant source of dissatisfaction, and may have to be discarded when the student emerges from his swaddling clothes. The stand which is purchased ought to be adapted to the receipt of optical apparatus other than the simple eye-piece and objective. It should have a jointed back, and be thoroughly steady in any position ; the adjustment should be easy and true, and if the body is twisted, any object observed should not be thrown out of centre ; the mirror should be plane and concave, and should have a long jointed arm; and the stage should be constructed for the reception of a condenser. Still more essential is it that the special optical parts, the eye-pieces and objectives, should be good. They should let through the largest possible amount of light (the diaphragm will easily control its quantity if needed), and there should be a complete absence of colour, both round the exterior of the field of view, and round any object, or particles of dust, in focus. The field should be flat, so that a small object moved from one part to another alters neither in distinctness, form, nor size. Lastly, the objective should have a fair working distance from the object, or the thickness of the cover-glass, to be hereafter noted, may become a matter of great importance.

In all these points, except perhaps accurate centering, the stands of English makers either equal or excel, price for price, the foreign stands ; while, on the contrary, price for price, the eye-pieces and objectives of continental makers usually are far superior to those made by the English opticians, a superiority probably due solely to the more trained skill and more patient accuracy of the workmen.

* Now Stiasuio.

Xvill

INTRODUCTION.

All of the work in this book, perhaps, with the excejDtion of Chapter XXI., can be performed with the aid of objectives np to ; but the student who has gained some experience will probably wish to add to his microscope one or more stronger objectives, in order to increase the range of his work. Increased magnification can be obtained by increased power either of eye-piece or of object-glass. All the objectives we have heretofore noted are what are called “ dry ” systems, since they are used for work in a dry state, and a layer of air separates the objective from the object. “Dry” objectives of high power are subject to great disadvantage from the serious loss of light their use involves. The light, in passing from the mirror to the objective, passes in the first place through air ; then the object-slide, next the object and the medium in which, the object is mounted, which may be glycerine, water, alcohol, etc., or even air ; then through the cover-glass, and finally through air again. In every one of these changes light is lost. Owiug to this loss of light, as well as for other reasons, it is not wise to use high power eye-pieces with dry objectives, added to which, as the eye-piece does not magnify the object, but only the image of it as given by the objective, any errors of this latter are likewise magnified by the eye-piece.

To obviate in part this loss of light, what are called “ immersion” objectives have been for the last few years much in use. In these objectives the cover-glass and the front lens of the object-glass are connected by a drop of liquid. . Such objectives are of two kinds ; “ water,” in which that is the liquid used ; and “ homogeneous,” in which the liquid is in general oil, or a mixture of oils, but sometimes is glycerine, etc. The homogeneous immersion objectives are dearer, less readily cleaned after use, and require a supply of the special fluid for which they are manufactured ; but on the other hand they transmit more light, bear a higher eye-piece, and are independent in their working of the thickness of the cover-glass. Dry objectives, and water-immersions, of high power are naturally dependent on the thickness of the cover-glass which the light-rays pass through after leaving the object. To provide for this, they are usually manufactured also with “correcting screw,” for use according to the thickness of the cover-glass, and at a somewhat increased price. The correcting screw accommodates the objective to the thickness of the cover-glass which happens to be in use, but a right use of it requires considerable experience, nor is it usually needed with any of the weaker immersion systems.

INTRODUCTION. '

xtx‘

An immersion objective, witliout correcting screw, is made to suit a certain medium thickness of cover-glass, which is usually stated by the optician, and it is therefore preferable for the beginner, if he wants such an objective, to use with it cover-glasses of this definite thickness.* On the correcting screw, where the system has it, are usually divisions and figures, which allow the focussing for any given thickness of cover- glass, where this is known. f But whoever does not fear the expense would do well to provide himself at once with a system for ‘‘ homogeneous immersion.” They are all constructed without correcting screw, since, as already indicated, the thickness of the cover-glass, of course within the permissible limits, is of no importance. By selecting a single such objective, say and purchasing a series of eye-pieces, one can obtain a range of possible magnification such as could only be given by several water-immersions, or dry objectives. A system for homogeneous immersion, provided it is perfectly constructed, can . therefore replace several systems of another kind.;};

Even in the smallest stands mentioned above, objectives for homogeneous immersion can be used with great advantage without any special apparatus for increasing the illumination ; but the highest capabilities of the homogeneous system are only brought out by the use of a sub-stage achromatic condenser. Several of the stands referred to above have sub- stage condensers constructed specially for them, and at a cost which, for these small microscopes, would rarely exceed £1 IO5.

Owing to the prevalent use of the standard screw of the Royal Microscopical Society of London, objectives of one maker can be attached to the instrument of another. Where this screw is not in use by the maker, the objective can have an adaptor attached. A point of some importance to English purchasers of continental objectives is this the customary length of the tube of the microscope on the Continent is 150 to 170 millimetres (6 to 7 inches), and the objectives are constructed to suit this length. If the tube exceeds this length, it should be stated in ordering the objectives, that they may be modified to suit. This is especially needed in ordering objectives for homogeneous immersion. All the microscope stands mentioned above have tubes of continental length, and most of continental size.

* On this subject see a note on page xxii.

+ Further information on this point in Chap. XXI., p. 224.

J Leitz, of Wetzlar, produces a -j'j of remarkable excellence, for £6 IO3.

XX

INTRODUCTION.

To give a theory of the formation of the microscopic image does not come 'within the range of our purpose, and for this we would refer to text-books on Physics and to special works on the mieroscope. Our task, on the other hand, will consist in making the beginner acquainted with the most important facts of microscopical botany, with the use of the microscope, and with microscopical manipulation. This instruction will be given by studies upon the objects themselves.

Besides the compound microscope to whieh we have hitherto exclusively referred, a simple, or so-called dissecting, microscope is also more or less necessary. For all the purposes of this book, and, indeed, for most botanical purposes, whether in anatomy or morphology, a dissecting microscope of very simple construction is all that is needed. Most such instruments are unnecessarily complex and expensive. Some, for instance, are constructed to magnify up to 60, 80, or even 100 diameters ; if such magnifying power is needed, the low power of the compound microscope will do equally well, dissecting being done upon the stage, but the arms being carefully supported. The following are a few typical simple mieroseopes, any one of which would suffice : —

Ross & Co.’s “ Magnifier Stand,” with two lenses of |-inch and ^-inch foeus, magnifying 20 and 40 linear, in flat morocco case, £2 2s.*

C. Collins, “ Dissecting Microscope,” with two lenses, to be used together or separately, 15s. (No arm-rests.)

Parkes & Son, “ Simple Microscope ” (No. 5030), on jointed arm, with universal movement, 15s. *

Swift & Son, “Simple Dissecting Microscope,” with three lenses, 18s. *

Zeiss, “Small Dissecting Microscope” (No. 117, Catalogue 1885), 18s., to which double lenses, magnifying 10, 15, or 30 diameters, at 6s. each (Arm-resbs).

The student can entirely dispense with a dissecting microscope, and dissect upon the stage of his larger instrument ; but as the image of the object is inverted, and any movements he may make are likewise reversed, he would probably be at first somewhat perplexed. Practice will overcome this difficulty ; or it can be cleared away at once by purchasing an “ erector ” for insertion in

• In these instruments the object is dissected on the table, or in any other convenient place. Those not marked have a special stage, with or without arm-rests, as indicated. See also p. 21 et seq.

XXI ijjtroductiona:

tlie draw-tube, costing usually 10s. or 10s. 6d. , It is desirable likewise to have a low power objective, e.g., 2-incb or l|-incb, though dissection Avith the 1-inch is perfectly simple. The lowest power eye-piece should be used. Dissection under the compound microscojDe has, with very small objects, this further advantage, that there is no chance of losing them in removing from one instrument to the other. To this may be added perhaps another advantage, in that the working-table is not cumbered with an extra instrument. For dissecting with the microscope the Avrists must be supported on a level with the object, or slightly beloAv it. Some dissecting microscopes have arm-rests for this purpose ; blocks of Avood of proper height, or even stacks of books Avill answer admirably.

A very necessary adjunct for microscopical work is a good magnifying lens, as it is often desirable first of all to study an object with it, afterwards using the microscope. The lenses of the dissecting microscope can be used as hand magnifiers, and low poAver objectives likewise make good hand lenses. It is worth while, however, to get a lens magnifying about six diameters; very convenient are the triplets, three lenses in a tortoise-shell case, usable separately or together, and sold at a price of about Ss. Qd. Remarkably beautiful are the PJatyscopic Lenses of Browning (63, Strand, London, W.C.), magnifying 15, 20, or 30 diameters, price IBs. Qd. each, and the Aplanatic Lenses of Zeiss, magnifying 6, 10, or 20 diameters, price 125. or 15s. each.

As it is desirable that the student should from the first begin to draw the objects he examines (practical instruction in Avhich will be found on p. 30 et seq.), it is desirable that he should have some form of drawing instrument to facilitate his work. DraAving can, it is true, be done without any such aid, but is more difficult. An apparatus for drawing (camera lucida) is constructed either for use with the body of the microscope placed horizontally, or placed vertically. Practically the latter is much preferable. Every microscope maker has appliances of his CAvn make, but they A^ary very much in real utility. Probably the best in existence are tAvo made by Zeiss, the new camera lucida of Abbe, price 305., or the camera lucida Avith two prisms, price 215. The former is specially constructed for the eye-piece No. 2 of Zeiss, and is mounted upon it ; it permits drawing upon a horizontal surface ; during observation it is removed. The second is slipped by means of a ring upon the tube or the eye- piece (any eye-piece of continental size) ; it

INTRODUCTION.

xxii

requires an inclined surface for drawing, but lias, however, the advantage that it is always kept upon the microscope, and during the observation is only pushed on one side. Both apparatus require drawing desks, Abbe’s camera a horizontal one, the drawing prism one inclined about 25°. The height of the desk should in general correspond with the height of the stage of the microscope. In specially long or shortsighted observers, it should be arranged according to the distance of distinct vision.

Most English opticians supply drawing prisms of one kind or another, capable of satisfactory work. None, however, in my experience, equal those of Zeiss.

A stage micrometer is likewise necessary. This can be obtained from most opticians at a cost of from 5s. to 10s., and ruled up to YoVo inch. - Zeiss has one at 10s. ruled to of a millimetre, i.e., about -2tVo inch.

Any steady table can be used by the microscopist for working, but it should be looked to that it is not too small, and not polished or varnished on its surface. This surface is best painted a dull, dark colour. The table is so placed that the microscope is about, or somewhat less than, two yards from the window. Any position of the window is good which allows a free outlook. From direct sunlight we protect ourselves by a white roller blind, which is best made of tracing-linen. The dazzling white light which we obtain . when the direct sunlight plays upon the blind gives the most favourable conditions for observation with high powers.

. The necessary object slides and cover-glasses can be obtained of most opticians. The former are procurable with either ground or . unground edges at a cost of about 4s. 6d. or 3s. 6<i. per gross, respectively. They are three inches long by one broad. The cover-glasses for ordinary observation should be ' about |-inch square ; but the observer should also have larger ones for specially large objects, and also others somewhat smaller (|-inch square) which will usually suffice for permanent preparations. If we use powerful objectives, it will be best to obtain these cover-glasses of \ definite thickness. For the beginner, this is not of special import- , ance ; but the more advanced student will find it advisable to procure both object-slides and cover-glasses of a definite thickness, *

* The latter, curiously enouf^h, are difficult to obtain in England, where, nevertheless, they are mostly made, and I get them from P. Stender, in Leipzig,

• Konigstrasse 11. They are 18 mm. square, lettered “ C,” at a price of 2». 6d.

’ ® See note on page xxiv.

INTRODUCTION. xxiii

Further necessary are • some .plane- and some hollow- ground . razors ; a fine and a coarse pair of steel forceps ; a finely pointed pair of dissecting scissors, for which fine embroidery scissors will .serve; a pair of needle-holders, somewhat after the fashion of crochet needle-holders, bnt so arranged that they will hold the finest needles firmly ; Engdish needles from No. 8 upwards, for these holders ; some scalpels, some fine painting brushes, a small vice, such as used by watchmakers ; some pij)ettes, glass tubes, and glass rods ; watch glasses of various sizes, and glass disks of suit- , able sizes for covering them; low glass bell-jars (receivers), in order to be able to fit up moist chambers ; zinc frames, somewhat; as represented in half -size in Fig. 1, on which to place the object-

PlO. 1.

slides under the bell-jars;* two bell-jars of suitable height, under which to -be able to place respectively the compound and the simple microscope ; and lastly, elder-pith. For working, a tumbler of clean spring water is needed ; a saucer is useful for dirty slides. “ The list of the necessary reagents is to be found at the end of this book. Where the word “ alcohol,” or “ spirit ” and not “ absolute alcohol,” is used, strong methylated spirits can always be understood and is far cheaper.

For the preservation of permanent preparations, many kinds of cabinets and cases are advertised. It is very important to re-

per 100. They are in square boxes, are very light, and come readily by post. Smaller sizes can be obtained, c.g. 15 mm. square, lettered “ C,” at 2s. per 100. These are all 010 mm. thick. At 0-15 mm. (B) thick these sizes are 2s. 3d. and Is. 9d. respectively.