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PRACTICAL BOTANY
BEGINNERS
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* — •
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PRACTICAL BOTANY
BEGINNERS
BY
F. O. BOWER, D.SC, F.R.S.
REGTUS PROFESSOR OF BOTANY IN THE UNIVERSITY OF GLASGOW
ftontron
MACMILLAN AND CO.
AND NEW YORK
I894
The Right of Translation and Reproduction is Reserved
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Richard Clay and Sons, Limited,
london and bungay.
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PREFACE
This little book contains, in an abridged form, the
elementary and more essential parts of the text of
the larger Course of Practical Instruction in Botany*
It is believed that beginners will find the directions
sufficient to guide their first steps in laboratory work.
The abridgment has largely consisted in the excision
of supplementary descriptions of forms other than
those which have been selected as the main types :
in so far as that is the case, the publication of this
book may be thought to encourage a narrow style of
type-teaching.
Type-teaching in Biological Sciences appears at
present to be inevitable in elementary classes ; it
lies chiefly with the teacher to avoid the evils which
are apt to arise from it. In order to use this book
with proper effect, his knowledge should extend far
beyond the area of the work here specifically de-
scribed, and the larger edition may help him towards
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PREFACE
this end. By grasping every opportunity of com-
parison of the type selected with allied forms which
show differences of detail, he will then be able to
guide the pupil to distinguish essentials from second-
ary details, and to check the dangerous tendency
of beginners towards generalisation from too limited
an area of fact.
F. O. Bower.
Glasgow, April 1894.
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TABLE OF CONTENTS
PAGE
List of Apparatus i
INTRODUCTORY CHAPTERS.
A. — Making Preparations 4
I.
-Adjustment of the Microscope 12
II. — Practical Exercises involving Simple Methods . 17
III. — Common Micro-Chemical Reactions 24
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CONTENTS
PRACTICAL DIRECTIONS FOR THE STUDY OF TYPES
PHANEROGAMS.
I. ANGIOSPERMS.
t VEGETATIVE ORGANS.
PAGE
A.— DICOTYLEDONS 34
Stem— HERBACEOUS TYPE.
Mature » . . . 35
Young 45
Apical Bud 47
ARBOREOUS TYPE \ 52
AQUATIC TYPE 67
Sieve Tubes 70
Laticiferous Tissues 73
Leaf — Bifacial Type.
Petiole 76
Lamina 77
Leaf-scars, and Fall of Leaf . < . . . 83
"Root— Herbaceous Type 85
Ligneous Type 88
Apex 91
B.— MONOCOTYLEDONS.
Stem— HERBACEOUS TYPE 95
ARBOREOUS TYPE 98
Leaf— Bifacial Type 100
Root 104
Apex 105
t REPRODUCTIVE ORGANS.
Observations with the Naked Eye 108
Development of the Flower ... 113
Calyx and Corolla 115
1
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CONTENTS
PHANEROGAMS {continued).
t f REPRODUCTIVE ORGANS {continued).
PAGE
The Stamen 116
Carpel and Ovules 119
Fertilization 120
Development of the Embryo 121
Development of the Endosperm .... 123
Mature Seed and Embryo. r
Dicotyledons 125
Motwcotyledons 127
Reserve and Transitory Materials in
Seeds, Tubers, &c 128
Germination.
Dicotyledons 132
Monocotyledons 133
II. GYMNOSPERMS.
t vegetative organs 134
Stem 135
Leaf 143
1 1 reproductive organs 145
Ripe Seed and Germination 149
PTERIDOPHYTA.
A.-LYCOPODINEjE.
SELAGINELLA (Heterosporous Type).
SPOROPHYTE 150
OOPHYTE 155
B.— FILICINEiE.
NEPHRODIUM (Homosporous Type).
MATURE SPOROPHYTE.
External Characters 156
Anatomical Characters to be observed
with the Naked Eye 157
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CONTENTS
PTERIDOPHYTA (continued).
Microscopic Observations—
PAGE
Stem 159
Root 168
Leaf 171
Sporangia 172
OOPHYTE 173
YOUNG SPOROPHYTE 177
BRYOPHYTA.
A.— MUSCI.
POIiYTRICHVM.
General External Characters .... 179
Microscopic Investigation —
OOPHYTE 180
SPOROPHYTE 184
B— HEPATICiE.
MARCHANTXA.
General External Character rs .... 189
Microscopic Observations 190
Sporophyte 196
THALLOPHYTA.
A.— ALGiE.
FLORIDEjE.
POLYSIPHONIA 197
PHiEOPHYCEiE.
FUCUS 201
CHARACEiE 2IO
CONFERVOIDEiE.
JBDOGONIUM 216
SIPHONEiE.
VAUCHERIA 219
CONJUGATE.
SPXROGYRA 223
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CONTENTS xi
THALLOPHYTA (continued.)
B.— FUNGI.
BASIDIOMYCETES.
PAGE
AGARICUS 226
iECIDIOMYCETES.
PUCCINIA 231
ASCOMYCETES.
BUROTIUM 236
PERONOSPOREiE.
PYTHIUM 241
MUCORINEiE.
MUCOR 244
SPORODINIA 245
ArPENDix A. — List of Reagents , their Preparation, and Uses . . 249
Appendix B. — List of the Reactions of Bodies commonly found
composing the Tissues of Plants 264
INDEX 269
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PRACTICAL BOTANY
BEGINNERS
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.
1. A pair of fine scissors with sharp points.
2. Fine-pointed forceps.
*3. One or more good razors (see p. 7), and a strop and
hone for sharpening them.
4. Scalpels of various sizes : a fine eye-scalpel with a
long narrow blade will be found to be very useful.
5. A section-lifter.
*6. Mounted needles.
7. Several fine camels'-hair brushes.
*8. 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.
*io. Test-tubes and beakers.
11. A spirit-lamp.
12. A black enamelled tile for mounting on.
*I3- Glass slides, with ground edges (3 in. x 1 in.).
*I4. Thin cover-glasses, square or circular (J in. diameter).
*I5. Blotting-paper, cut or torn into small pieces.
* 3 B
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PRACTICAL BOTANY
*i6. Drawing-paper or card, with a hard smooth surface, or
a note-book of such paper, without lines.
*I7. Hard pencils (H. or H.H.H.) and india-rubber.
*i8. Gummed labels (i in. x J in.) for naming slides.
*I9. A coarse duster, and a finer cloth, e.g. an old pocket-
handkerchief.
20. A rack for keeping slides temporarily, and a bell-glass
to cover it.
*2I. A simple lens.
*22. A compound microscope. This should be one of the
smaller stands with a short tube : such stands of varying merit
are to be obtained from most 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 of about 1 inch
focal length. The higher about one-sixth inch or
one-eighth inch focal length.
*iii. A micrometer, either adapted to the eye-piece, or a
stage micrometer,
iv. A nose-piece to carry two, or, if necessary, more
objectives : its use will save much time,
v. A camera lucida for drawing.
*23. A rack or tray to hold small glass-stoppered bottles
containing reagents : the following are the reagents which are
in most constant use —
*a. Weak 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
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.
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APPARATUS
*e. Chlor-sinc-iodine (Schulze's solution) may be pur-
chased ready prepared from the dealers in
micro-chemical reagents ; or it may be prepared as
follows : —
(i) Dissolve no grms. of zinc in 300 c.c. of pure
hydrochloric acid, and evaporate to 1 50 c.c. (sp.
gr. about r8).
(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.
*f. 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
colourless.
*g. A solution of common salt : a 5 per cent, solution,
i.e. 5 grms. 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 mount-
ing 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 cleansed 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.
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I
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. — For the general study of the histology of the
mature parts of plants, it is often unnecessary 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 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 be large relatively to
the bulk of the object, and that the fluid have 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.
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MAKING PREPARATIONS
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 — 0-5 per cent, solution in water).
4. Osmic acid (1 — r 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 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 produced much
more rapidly ; in the case of simple structures, such as unicel-
lular or filamentous Algae, a few minutes (5 — 15) 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
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PRACTICAL BOTANY
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.
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. i), which may be
taken to represent the transversely cut end of a cylindrical
stem, the tissues being arranged with reference to a central
point (e) : transverse sections are those which are in transverse
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CUTTING SECTIONS
planes, parallel to the plane of the paper in Fig. i. 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. I : a radial section (a e b) includes the
organic axis (e), and a slice of tissue thus cut when examined
from a direction indicated 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 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 (t\e. the part near to y y) is to be examined, for ob-
viously in the more lateral parts of the section (c D) the radial
lines are not cut 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 instrument : 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 serve for sections of large area ;
for such work a razor with one flat side is recommended. For
general use, not only in cutting small objects and soft tissues,
but for the every-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.
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8 PRACTICAL BOTANY
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.
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 ; they should cultivate that
small amount of manual dexterity which will suffice for the
successful preparation of such objects as will be described
below.
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 convenient 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 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
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EMBEDDING
mixtures of substances, are used for this purpose, of which soft
paraffin is perhaps the best. Samples of paraffin which vary in
hardness and melting point may be obtained from the dealers.
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 with-
out unnecessary delay a small quantity of the embedding sub-
stance, melted over a 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.
The sections when cut should be removed at once to a
watch-glass containing alcohol or water, by means of a camels'-
hair brush, or a jet of alcohol or water from a wash-bottle : the
thicker sections may then be removed, and the thinnest ones
selected for observation.
V. Mounting Objects. — Various specimens, whether sections
or objects which may be examined whole, require varied
treatment, and the common methods in ordinary use will be
described below, and illustrated by experimental exercises (see
pp. 17, &c.) ; meanwhile a few practical suggestions will be
given which are to be observed in all cases, whatever the
special method of treatment may be.
1. Study to avoid all unnecessary manipulation of specimens :
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PRACTICAL BOTANY
never apply a reagent at haphazard, but only when you have a
definite purpose for doing so.
These rules apply specially to staining reagents, which
should only be used when their assistance is actually required :
the primary end of the anatomical investigations detailed
below is not to prepare a number of objects pleasing to the
uneducated eye, but to gain a knowledge of the structure of
the plant-body as it is in the living state, and this end may as
a rule be best attained by the simplest methods.
2. See that the glass slide and the cover-glass are perfectly
clean and dry, and show a bright polished surface before using
them ; they should be cleaned immediately before use, and,