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THE LIBRARY

OF
THE UNIVERSITY

OF CALIFORNIA

DAVIS

• •

*■

■

* —

^.^:

HANDBOOK

PLANT DISSECTION

J. C. ARTHUR, M.Sc,

Botanist to the New York Agricultural Experiment-Station^

CHARLES R. BARNES, M.A.,

Professor of Botany in Purdue University^

AND

JOHN M. COULTER, Ph.D.,

Professor of Botany in Wabash College \

EDITORS OF THE
BOTANICAL GAZETTE.

NEW YORK

HENRY HOLT AND COMPANY

1886

i JlRR AR Y

HENRY HOLT & CO.

■

Press of W. L. Mershon 8c Co.,

Rahway, N . J,

PREFACE.

A rich harvest of laboratory manuals has resulted to
zoology from the publication of Huxley and Martin's Ele-
mentary Biology ten years ago. Although that work
embraced both animals and plants with over half the
examples from the latter, it has given rise to no similar aid
to botanical study till the past year. The increasing
laboratory facilities in this country seem to warrant the
expectation that an elementary manual like the present
work will now be found in many instances to afford wel-
come assistance to both teacher and pupil.

In 1882 one of the authors of this book drew up an out-
line of work for a few plants, which was used in the Summer
School of Science of the University of Minnesota. Not
long afterward the preparation of the present hand-book
was actively undertaken by the three authors conjointly,
and has since been gradually perfected and tested by
repeated use with classes and individual students.

Although the present work is based upon Huxley and
Martin's in form and mode of treatment for the laboratory
part, it differs in excluding all matters of physiology so far
as possible, as the present demands of vegetable physiology
will hardly permit harmonious treatment along with a course
of dissection.

In drawing up the outlines of work the aim has been to
direct the student in a very careful and systematic exam-
ination of a few examples, so that while he is securing a
knowledge of the main features of plant anatomy, he will

PRE FA CM.

at the same time acquire the habit of close and critical
observation, which is indispensable to the successful pros-
ecution of natural history studies. To this end the direc-
tions for finding the different parts have been made as
explicit as possible, and at the same time as little informa-
tion given about them as seemed' advisable ; for the
student having found the part is expected to examine it
thoroughly until he has found out all that may be readily
seen. This rule has been modified according to the diffi-
culties to be overcome, and in extreme cases full information

has been provided, which the student is only expected

. On the other hand, it will repeatedly happen that
more may be learned by an acute observer than there
is any hint of in the outlines, as the work, though
deemed sufficiently exhaustive for the student, is far from
being so for the specialist.

In the use of such outlines as these there is alwavs
danger that the student will slight the study of those parts
which he is expected to work out for himself and only
attempt to verify the portions where the information is
fuller. If it be found that too great dependence is being
placed on the manual it will be advisable to substitute
plants allied to those named, thus withdrawing all exact
information ; the laboratory directions will still serve as a
guide to the order and methods of examination.

It has been no part of the present aim to provide a key
to the nomenclature of plant anatomy. When tech-
nical terms are used, as indeed is necessarily very frequent,
they have usually been preceded by descriptive definitions,
either direct or implied. A glossary is added to further
assist the student, so that he may find as little difficulty with
the names as possible, and devote himself chiefly to the
objects themselves. On this account, and on account of the
progressive series of forms which have been chosen, it is

PREFA CE.

hoped that the work will be found suitable not only for
classes pursuing a regular course of lectures, but also for
those who have never before studied botany, and for
home use away from the assistance of a teacher.

The required apparatus, reagents and materials have been
reduced to a minimum, difficult manipulations (except the
cutting of sufficiently thin sections) have, to a large extent,
been excluded, and the minute anatomy has been kept
within the limits of the average microscope used in the
botanical laboratories of this country. In short, the attempt
has been to provide a guide to the study of a few common
plants in which simple appliances, coupled with persever-
ance and keen observation on the part of the learner, are
the only essentials.

Under "gross anatomy " the plant is first examined with
the aid only of a hand lens, and then passing to " minute
anatomy," every part is subjected to the compound micro-
scope. A student's success in the latter may often be
gauged by his ability to discover all there is to be seen
under the former.

The laboratory work for each plant is preceded by direc-
tions for the preliminary finding and preparation of mate-
rial. It is followed by annotations which serve a number
of purposes : (i) to explain obscure matters, (2) to give
additional information which for want of higher powers,
special reagents or proper materials, the student is unable
in the usual limited time to secure for himself, but which is
essential to fully round out the subject, more especially,
however, (3) to give some insight into the course of develop-
ment from the lower to the higher forms which will serve as
a thread on which the most important facts ascertained in
the laboratory work may be strung, and not the least (4)
to direct the student to sources of additional information by
means of which he may pursue his inquiries as far as he

Vl PREFA CE.

may choose. The annotations are necessarily fragmentary
and disconnected, and the references to literature only
sufficient to start the student in his researches.

January, 1 886.

The Authors.

CONTENTS.

Illustrations in Gross Anatomy

Explanation of Plate I,

Illustrations in Minute Anatomy.

Explanation of Plate II,

Introduction.

Instruments,

Section cutting, -
Mounting,

Applying reagents,
Care and use of material.
Drawing, -
Books of reference,

Green Slime {Protococcus viridis)

Preliminary, -
Laboratory work,
Annotations, -

Dark Green Scum (Osc Maria tenuis)

Preliminary, -

Laboratory work,
Annotations, -

Common Pond Scum {Spirogyra quinind)

Preliminary, -
Laboratory work,
Annotations, -.

t •

Xlll

Reagents, ._.---

Care and use of microscope and lens, 6

*5
16

23
25

28
29

34
39

• • *

vl11 CONTENTS.

White Rust {Cyst opus candidus).

Preliminary,
Laboratory work,
Annotations,

Lilac Mildew {Microsphcera Friesii)

Preliminary, -
Laboratory work,
Annotations, -

Common Liverwort {Marchantia polymorphd).

Preliminary, -

Laboratory work, -
Annotations, -

Moss {Atrichum undulatuni).

Preliminary, -

Laboratory work,
Annotations, -

Maiden-hair Fern Adiantum pedatum)

Preliminary, -
Laboratory work,
Annotations, -

Scotch Pine (Pinus sylvestris).

Preliminary,

Laboratory work,
Annotations,

Field Oats {Avena sativa).

Preliminary, -
Laboratory work,
Annotations, -

44
48

52
52

84
86

103
105
124

130
132
161

172

172
192

CON TEN TS. ' i x

Trillium {Trillium recurvattwi)

Preliminary,
Laboratory work,
Annotations,

Shepherd's Purse {Capsella Bursa-pastoris)

Preliminary, -
Laboratory work, -

Annotations, - - - -

Glossary,

Index,

197
198

215

222
223
236

- 243

25 '

EXPLANATION OF PLATE I.

ILLUSTRATIONS IN GROSS ANATOMY.

Fig. I. Diagram of an open flower of Trillium showing the
number and relative position of the parts : s sepals, p petals, st
stamens in two whorls, c carpels each bearing two ovules. — Drawn
with pen.

Fig. 2. Diagrammatic drawing of Marchantia to show the mode
of branching, somewhat enlarged. As one branch of each new
dichotomy soon distances the other, it produces the appearance of a
main axis with right and left branches : an the extension into
an antheridial branch, ar extension into an archegonial branch, y
recent dichotomy, o o% older dichotomy in which o9 is already per-
ceptibly longer, c cupules which arise at the growing end of the
midrib and are left upon its upper surface as the stem advances.
Drawn with pencil.

Fig. 3. Flower of radish, greatly enlarged and modified by the
growth of Cystopus within it, natural size. The change induced
by Cystopus is variable, sometimes single flowers are enlarged, as
in this case, sometimes the whole cluster of flowers is changed
when the individual flowers remain smaller. This example is
larger than the average size. — Drawn with pencil.

Fig. 4. A small fruiting plant of Atrichum, X 2 : the stem bears
scale leaves below and foliage leaves above, the base is clothed
with rhizoids that simulate roots, st seta, sp capsule sur-
mounted by the closely fitting calyptra. The distance the beak
extends into the calyptra is indicated.— Outline drawing with pen.

Fig. 5. Flowering head from a vigorous male plant of Atrichum,
X 2 : the difference between the perichsetial and foliage leaves is
well shown. — Drawn with pen.

Fig. 6. Pod (seed vessel) of Capsella, X 2.— Drawn with pen.

Plate I. —Gross Anatomy.

X 4 00

ue.

X 100

X430

Plate II. -Minute Anatomy.

EXPLANATION OF PLATE II.

ILLUSTRATIONS IN MINUTE ANATOMY.

Fig. 7. One of the pair of fibro- vascular bundles in a leaf of

Pinus, x 400 : p

of spiral vessels (in

other bundles they are often more scattered), m m rows of paren-
chyma cells forming medullary rays containing starch in the xylem
and protoplasmic substances in the phloem, r resin duct, f f
fibrous tissue with thick walls, small cavities and prominent middle
lamellae, f9 fibrous cell with lateral pit 9 pa thin-walled parenchyma,
tr tr1 parenchymatous tracheides with bordered pits, tr9 face view
of the pits on an end wall. The other bundle of the same leaf was
at the left side of this one. — Drawn with pen.

Fig. 8. Diagrammatic drawing of a vertical section of leaf of
Capsella showing a sorus of Cystopus, X 100 : ue upper epidermis,
le lower epidermis,/ palisade parenchyma, s spongy parenchyma,
fb small fibro-vascular bundle, h hyphae passing between the pali-
sade cells and terminating in c the conidiophores which bear the
chains of conidia c'. The epidermis is raised, but not yet ruptured,
above the sorus. — Drawn with pen.

Fig. 9. Cells of Protococcus after treatment with chlor-iodide
of zinc, X 430 : w the thick cell wall, c large chlorophyll bodies,
;/ nucleus with central nucleolus. — Drawn with pencil.

Fig. 10. Diagrammatic drawing of a transverse section through
the ovary of Trillium showing one entire carpel, which is shaded,
and a portion of the other two, X \2\ ww the pair of wings,// the
three placentas meeting in the center of the ovary, x xylem and p
phloem of the fibro-vascular bundles of which each carpel has one
between the wings and one in each placenta, o ovule which re-
ceives a branch from the fibro-vascular bundle of the placenta to
which it is attached. — Drawn with pencil.

Fig. 11. Diagram to illustrate the theoretical carpellary struc-
ture of Trillium, representing a single carpel in transverse section

as in fig. 10, and with the same lettering. — Drawn with pen.

INTRODUCTION.

I. INSTRUMENTS, ETC..

Following is a list of the instruments and appliances
necessary and desirable for use with this manual.
Those printed in italics are necessary ; the remainder
are desirable but can be dispensed with.

GROSS ANATOMY.

Hand lens,
Dissecting needles,
Razor or scalpel,

Glass slips (3),
Cover glasses (6),
Drawing materials,
Holder for lens,
Dissecting microscope,
Fine forceps,
Fine scissors,

■

Camel's-hair brush,
Metric rule.

MINUTE ANATOMY.

Compound microscope,
Razor or scalpel,
Glass slips (12),
Cover glasses (24),
Fine forceps,
Dissecting fieedles,
Drawing materials,
Blotting or filter paper,
Camel's-hair brushes,

Fine scissors,
Watch glasses,
Dropping tube.

The hand lens should have a magnifying power of
eight to fifteen diameters; one of ten or twelve diam-
eters is the best. Such a glass costs from 50 cents to
$5.00, according to quality and mounting. One costing
$1.00 will be found sufficiently good.

A holder for the lens may be constructed as follows
and answers every purpose of a dissecting microscope :

2 IN TR OB UC TION.

Take a block of wood about 10 cm. long and 6 cm.
wide. Fix upright in the middle of the block about
2 cm. from one end a bit of metal rod of 3 to 4 mm.
diameter and 6 to 8 cm. high. Bore a hole a little to
one side of the center of a smooth cork so that it will
slide smoothly on this rod. Bore another hole at right
angles to the first through which pass a wire of 7 to 8
cm. length. The free end of this wire may be bent into
a loop or circle as may be desired to hold the lens.1 The
lens may be focused by sliding the cork up or down.
Cheap loupe holders are also to be had of dealers in
optical goods.

The mounted needles ran be better made than bought.
Take two number 8 " sharps/' break off about one-third
of the needle from the blunt end and grasping the remain-
der firmly with a pair of pliers, push the blunt end into
a pine pen-holder or any suitable piece of soft wood

till firm. The points of the needles should be kept
sharp.

The razor should be of the best quality of steel
without any stamped lettering or even etching on the
blade, which should be at least 2 cm. wide. The
best shape for the blade is to be ground flat on the
'under side (when held in the right hand with the edge
toward one) and hollow on the upper. Next to this
shape the " hollow ground " razor is best, provided the
thin part of the blade is at least 12 mm. wide and not
so thin as to be easily bent. " Extra hollow ground "
razors have the blade too thin.

Glass slips with ground edges may be purchased of
any dealer in microscopical supplies or they maybe cut

1 Modified from Kingsley, The Naturalist's Assistant, p. 83.

IN TR OD UC TION. 3

from clear window glass, or better from photo-
graphic plate ; 76 mm. (3 in.) by 25 mm. (1 in.) is the
standard size.

Cover glasses must be bought. They should be 15 to
20 mm. in diameter or square. No. 2 thickness is pref-
erable.

The compound microscope should be of good work-
manship, which can be best secured by buying of some
reputable maker. A small low stand is to be pre-
ferred. It should have a good fine adjustment and be
furnished with two good objectives, viz., a 1 in., f or
and a J, \, or £, and two eye-pieces, viz., A and C, or if
only one, a B. A combination of either eye-piece with
the 1 in., f, or § is in this manual designated as a " low
power" ; similarly, a combination with the J, \, or \
is known as a " high power." There should also be a
camera lucida, and a micrometer ruled in fractions of a
millimeter.

Fine forceps should be of steel, have very slender
bent points, and come together accurately. Those used
by dentists are excellent.

A large earner s-hair brush is desirable for dusting off
lenses. A small one with long hairs, which tapers to a
sharp point when wet, is very convenient for removing
sections from the razor. It should be mounted on the
small end of a pen-holder, in the large end of which is
a short needle. By sticking this in the table the brush
may be kept out of the dust and always handy.

Watch-glasses should have a flat bottom to prevent
tipping too easily. Plain individual salt-cellars answer
the purpose admirably.

A dropping-tube is a piece of small glass tubing drawn

4 INTRODUCTION.

to a point, with a rubber bulb on the larger end. They
may be purchased in drug stores under the name of
" medicine droppers."

Fine scissors may be either those made for anatom-
ical purposes or small embroidery scissors. The
latter answer most purposes well.

A metric rule is highly desirable. The student
should have a pocket rule and should early familiarize
himself with the metric system. Metric measures of
various styles and prices may be obtained of the Amer-
ican Metric Bureau, Boston, Mass.

The drawing materials required consist of slips or a
blank book2 of unruled paper, hard and soft pencils,
pens and ink. For ink drawings the paper may be
either sized or unsized, rough or smooth, so long
as the ink does not spread, but for pencil drawings
the surface must be minutely roughened, and with-
out sizing, in order that the plumbago may adhere well
and give a soft effect. A quite hard pencil, No. 5, VH
or HHHH, of artists' grades, is needed for tracing
under the camera lucida, and one slightly softer than
used for ordinary writing, No. 2, SM, or B, for com-
pleting drawings, especially those in gross anatomy.
Ordinary steel pens, preferably those with slender
points, and common black ink will suffice, but finer
work may be done with lithographic pens and India
ink.

II. REAGENTS.

The following reagents are necessary for the study
of minute anatomy with this manual :

2 If a book is used it must be so bound that it will lie flat on the table
when open. The slips are usually preferred.

INTRODUCTION. $

Alcohol, Magenta,

Potassic hydrate, Glycerine,

Iodine, Sulphuric acid,

Chlor-iodide of zinc. Potassic chlorate solution.

The alcohol used is the commercial article, 95 per

cent. pure.

The potassic hydrate is a 5 per cent, solution of
potassic hydrate in distilled water. Sodic hydrate will
answer the same purpose. The " liquor potassae " of
the U. S. Dispensatory is of this strength and may be
purchased of any druggist.

The iodine is prepared as follows : Dissolve 3 gm. of
iodide of potassium in 350 cc. of distilled water ; add I
gm. of sublimed iodine. A weaker solution will be
useful, viz., potassic iodide 3 gm., distilled water 500
cc, iodine 1 gm. The tincture of iodine diluted till it
is a sherry brown color will answer in some cases, but
is not so generally useful as the solution recom-
mended.

Chlor-iodide of zinc may be prepared as follows: Dis-
solve metallic zinc in concentrated hydrochloric acid
until the action ceases ; evaporate to the consist-
ency of syrup in contact with metallic zinc ; saturate
this with potassic iodide ; add as much iodine as it will
take up, with some excess.' It is better to keep the
solution in a dark place, although in the majority of
instances the proper reaction will be secured without
this precaution.

Magenta is a solution of the aniline color of that
name. It may be purchased of dealers in microscopi-
cal supplies or made as follows : Powder 1 gm. crystal-

3 Poulsen and T release, Bot. Micro-Chemistry, p. 8.

6 IN TR OD UC TIOAT.

lized magenta. Dissolve in 160 cc. distilled water, to
which I cc. of alcohol has been added.4

The best commercial glycerine should be used. See
that it is colorless and free from sediment.

A 75 per cent, solution of sulphuric acid should be
prepared by mixing three volumes of c. p. sulphuric
acid with one volume of distilled water, being very
careful to pour the acid slowly into the water while

stirring it.

The potassic chlorate solution may be prepared as fol-
lows : Dissolve 2 gm. potassic chlorate in 5 cc. nitric
acid.

III. USE OF THE MICROSCOPE AND LENS.

The prime requisite in the use of any optical instru-
ment is cleanliness: dirty lenses frequently defeat the
very object of their use, namely, clearer vision. Before
beginning to work with either the simple or compound
microscope, see that the lenses are perfectly clean.
When a lens needs cleaning, take a camel's-hair brush

and brush away all particles of dust. Then wipe gently
with a piece of soft unstarched linen or cotton — an old

handkerchief is the best — breathing upon the surface

slightly if necessary to remove the dirt. Too great care

can not be taken to avoid scratching the polished surface

of the lens ; hence the least possible effective pressure

should be used when wiping it. If properly handled

after they have once been cleaned, lenses will seldom

need any thing but brushing. One should avoid with

the greatest care touching the surface of a lens with

4 Huxley and Martin, Biology, p. 269.

INTRODUCTION. 7

the fingers, as finger marks are difficult to remove : no

matter how clean the skin, the oil from it will adhere to
the glass and can only be perfectly removed by wiping
with linen moistened with alcohol.

When the lens is held in the hand to examine ob-
jects, rest the hand holding the lens on the hand hold-
ing the object. They will then tremble together. The
eye should be as close to the lens as possible in order
to obtain a wider field of view.

In using the compound microscope the front only of
the objective and both surfaces of both lenses of the
eye-piece need cleaning. If the eye-piece be dirty there
will be specks in the field of view when there is no ob-
ject on the stage. These can be made more apparent
by turning the eye-piece in the tube while looking
through it. In like manner by partly unscrewing the
eye lens and turning it, it may be discovered whether
the eye lens or field lens is dirty. If the front of the
objective be dirty it will be manifested by a dimness
and want of definition of the outlines of objects, affect-
ing the whole field of view.

In focusing with the high power of the compound
microscope, first rack the objective down as close to the
cover-glass as possible while watching it from one side.
Then look through the tube, rack slowly back and
watch for the coming of the object into view.

Never rack downwards while looking through the
tube unless the object be in view.

Do not use the fine adjustment until the object is
nearly in focus with the coarse.

Raise the objective slightly before placing or remov-
ing a slide.

8 INTRODUC TION.

An object is examined by " direct" light when it is
examined by the light which falls upon its surface with-
out passing through it. This is the common method
with the hand lens.

An object is examined by " transmitted " light when
the light passes through it before entering the eye.
This is the common method with the compound mi-
croscope. Ordinarily, when transmitted light is used,
direct light should be cut off as far as possible.

An object is examined by u oblique " light when the
light passes through it so obliquely that only that re-
fracted by the object enters the eye. It therefore ap-
pears light against a dark ground.

IV. SECTION CUTTING.

Sections. — A section is a very thin slice taken from the
interior of any organ. It should be of as nearly equal
thickness in all parts as possible. The term " slice " is
used to designate a thin piece cut from the surface of

any organ.

By a transverse section is meant one at right angles
to the long axis of the object. Unless care is exercised
the surface from which the sections are being cut will
become inclined. Especially is this likely when the
object is large or is supported in pith. The pith stick
should be trimmed down at the end so as to leave only
enough to support the object. The chief cause of the
tendency to become inclined is that the under side of
the razor is not flat ; hence the larger the object, the
more likely the transverse sections are not to be truly

transverse.

By a longitudinal section is meant one which is

L V TR OD L/C TION. 9

parallel to or includes the long axis of the object. It is
evident that longitudinal sections of all cylindrical ob-
jects may be either radial or tangential. A radial
section is one lying in the plane of a radius. A tangen-
tial section is one parallel to a plane tangent to the
cylinder.

Longitudinal sections are much more difficult to
make than transverse and they are nearly or quite use-
less unless truly longitudinal.

The razor. — The secret of making good sections
lies in having and keeping a sharp razor. No
amount of skill can make a dull razor cut a thin
section.

The edge of the razor must be free from nicks. This
can be determined by looking at the profile of the edge
against a bright light with a lens. Nicks, if small, can
easily be taken out on a hone.

The razor should be stropped often. It is easier to
keep it from getting dull than to sharpen it after it has
become so. If its edge is free from nicks and it will cut
a hair of the head 2 cm. from where it is grasped by the
fingers, it is in good condition.

After using the razor be careful to see that no mois-
ture or plant juices are left on the blade; they will
surely rust it if allowed to remain.

Holding specimens. — Large specimens of which
sections are to be cut may easily be held in the
fingers. They should be held vertical, grasped
by the fore-finger and thumb of the left hand
so that the razor blade may rest on the cor-
ner of the fore-finger, and the remainder of the hand
be out of the way below.

I o IN TR OD UC TION.

Small objects should be placed in a piece of elder or
sunflower pith in which a median longitudinal slit has
been made, deep enough to allow the ends to spring as
far apart as necessary to receive the specimen, between
which it is to be firmly held. The pith is then to
be grasped as a large specimen for cutting. If alcoholic
specimens are being used the pith should be pre-
viously soaked in alcohol, and if fresh material, in

water.

Cutting. — Grasp the razor firmly with the right hand
where the blade joins the handle, bracing the blade by
resting the thumb against the tang. Hold the razor hor-
izontal, rest the under side of the blade against the corner
of the fore-finger and cut toward you, pushing the razor
from point to tang or drawing it in the opposite
direction, using as much of the blade in cutting as
possible.

If the object be flat and thin, as a leaf, let the razor
edge pass through it at an angle of 200 to 300 to its
length.

If alcoholic specimens are being cut, the razor blade
should be flowing with alcohol. The oil usually on the
blade from stropping will prevent the alcohol from run-
ning off, unless the blade be considerably inclined. If
fresh material is used the razor should be dipped in
water. The object of the operation in both cases is to

prevent the section from becoming dry. Should it do
so, it will inevitably contain air bubbles when mounted,
which will unfit it for examination.

Removing the sections. — The most convenient thing
for removing sections from the razor is a small camel's-
hair brush, which, when wet, tapers to a sharp point.

TN TROD UC TION. 1 1

With such a brush a section may easily be picked up
from the water or alcohol, in which it ought to be
floating on the razor, and transferred either to the slide
or to a watch glass. An easier way of removing sec-
tions which are to be transferred to a watch glass, is
to wash them down to the point of the razor, and then
dip the point of the blade in the liquid in the watch

glass.

Always cut a number of sections — half a dozen or

more — at once. One or more may prove good.

V. MOUNTING.

Previous to mounting any specimens, it must be seen
that the slide and cover glass are perfectly clean.
Nothing is better for cleaning slides and covers than a
clean linen handkerchief, which should be used for this
purpose alone. The cleaning of the slide is a simple
operation ; the cleaning of the cover requires more care,
to prevent breaking. Having dipped the cover in clean
water, take it between the thumb and fore-finger, over
which a single thickness of the handkerchief has been
thrown. Wipe gently, using the fingers of the other
hand to keep it in place. The surfaces of the cover
should be perfectly cleaned, so that when light is
reflected from them, no oiliness or dust is visible.
Having cleaned the cover, lay it down in some clean
place, with one edge projecting slightly, so that it can
be readily picked up, or stand it on edge against some
support.5 Having placed the desired specimen

5 A very convenient receptacle for covers, whether clean or dirty, is
made by sawing several grooves in a block of wood, and nailing across
the ends of the grooves a thin strip. In these grooves the covers rest on
edge. A similar arrangement is useful for slides.

I i IN TROD UCTIOrf.

in the center of the slide in a drop of water,
grasp the edge of the cover firmly with the fine
forceps, breathe on the under side, hold it in a slanting
position over the drop of water, place the lower edge
in the edge of the drop, and lower it gradually on the
water. The condensed moisture of the breath insures
more ready contact of the water with the cover, and
lowering the cover slantwise gives opportunity for the
escape of air from under it.

If air bubbles appear in the mounting, they are due
to one of two reasons : either (i) the cover glass was
not clean, or (2) it was dropped instead of being low-
ered to the slide. Of these the first is the more com-
mon cause of air bubbles. They may sometimes be
removed by lifting one edge of the cover with a needle,
while the other is prevented from slipping, and then
lowering again. Sometimes it will be necessary to
remove the cover, clean and replace it.

If the bubbles appear in the specimen itself, they are
probably caused by allowing the section to dry partly
before mounting. They may usually be removed by
taking off the cover and treating the specimen with

alcohol.

The worker should not be content to let bubbles

remain.

Another difficulty is sometimes encountered, when

it is attempted to mount several sections under the
same cover, in the floating out of one or more. This

is usually due to an excess of water. The remedy is to
take up the cover, absorb some of the water with filter
paper, and re-cover.

After covering specimens, soak up the superfluous

INTRODUCTION. 13

quid sufficiently to prevent the cover floating when
the slide is inclined.

VI. APPLYING REAGENTS.

Stains are most conveniently applied by placing a
drop of the liquid at the edge of the cover, and allow-
ing it to run under, hastening the process when desired
by placing a strip of filter paper at the opposite edge.
If the stain does not reach all parts of the specimen,
the cover glass may be slightly raised. It is quite
important in many cases to watch the action of reagents.
In such a case they should be applied with the stage of
the microscope horizontal. Time may be saved when
it is necessary to examine specimens in potash, by
placing a drop of potash on the slide, and mounting
directly in that medium. In all cases, as soon as the
specimens have become clear, the potash should be
washed out with water: otherwise the cell walls swell
excessively, and many points become indistinguishable.
It should be remembered in examining specimens
treated with potash that many cell walls are somewhat
swollen, and that the longer they remain the greater
the swelling becomes.

■

Glycerine is one of the most useful media for clear-
ing, and at the same time preserving specimens for
prolonged examination. Whenever it becomes desir-
able to preserve specimens from one day to another, a
drop of glycerine should be applied to the slide, so
that it just touches the edge of the cover, and the slide
laid away in a horizontal position. As the water or
alcohol evaporates, the glycerine will run under the
cover. The excess may be wiped off with a damp rag

14 IN TROD UC TION.

after a few hours. Specimens may be mounted directly
from alcohol or water in glycerine, but the saving in
time will not be material, unless it is known that the
specimens are good, before mounting. Care must be
taken that the glycerine does not overspread the cover,
which, under such condition, must be taken off and
cleaned. Most specimens may remain in glycerine any
length of time without deterioration, and will become

Care must b

keep the specimens thus preserved free from dust.

They must be handled cautiously, lest the cover be

shoved off. If desired, specimens which have been

preserved in glycerine, may be permanently mounted,

by simply running a ring of shellac cement around the
cover.6

The greatest care must always be exercised to pre-
vent reagents from coming in contact with the stand
of the microscope or the lenses, as most of them attack
the lacquer of the brass work, and some the brass.
The chief danger arises from a failure to remove the
excess of the reagent, which then collects at the lower
edge of the slide when the microscope is used in an
inclined position, and runs off on the stage. Sulphuric
acid behaves in the same way even when the
is once removed, if it is allowed to remain any length
of time, because it absorbs moisture from the air.

Boiling specimens in the potassic chlorate solution
should not be done in the same room with the micros-
cope as the liquid and its fumes are intensely corro-
sive.

6 For directions for making this cement, see Am. Mo. Mic. your., vt
(1884), p. 131. Similar cements may be bought.

IN TR OD UC TION. 1 5

VII. CARE AND USE OF MATERIAL.

Throughout the directions for laboratory work it is
understood that material preserved in alcohol will
answer unless otherwise stated. In many cases only
alcoholic specimens are usable and in other cases only
fresh specimens.

Do not tear up specimens needlessly.

Examine a specimen thoroughly and see as much as
possible before dissecting.

Do not begin dissecting a part until it is decided
what to look for and where to look for it.

Be economical ; chiefly because it is a good habit,
secondarily because material costs time, or money, or
both.

Save the pieces ; they may be useful in future work :
it is easy to throw away ; it is more difficult to gather.

Preserve all sections and other preparations until the
study of the plant is completed.

When the specimens are mounted in water be care-
ful lest they become dry by the evaporation of the
water. It can be most conveniently replaced by plac-
ing a brush charged with water at the edge of the

^ V* ~~~ ^..^.^

cover opposite the area of air. As soon as the air is
displaced the brush should be removed.

When studying particular tissues in a section the
thinnest parts of each tissue should be selected. It is
rare that a section is so uniform that the tissues are
equally well shown in all parts of it, and different tissues
must not infrequently be looked for in different sec-
tions. It is best therefore to look well over the speci-
mens before settling to the study of any tissue.

In order to obtain a clear conception of the shapes

1 6 IN TR OD UC TION.

of the cells of a particular tissue, it is indispensable that
the student carefully compare the transverse and longi-
tudinal sections of the cells. Moreover the longitudi-
nal sections must be compared with the transverse to
determine their position.

It frequently becomes necessary to examine a toler-
ably thick object. In such a case, very different views
of the object will be obtained as the focusing screw of
the fine adjustment is moved. It must be remembered
that a good objective gives a clear image of only a
single plane at one time, though adjacent images
modify this somewhat. Hence it is easy to determine,
knowing in which direction the objective is moved by
the focusing screw, whether one object is above or
below another.

The use of the fine adjustment must be learned as
soon as possible and must be assiduously practiced.
The finger should be kept on the fine adjustment most
of the time when using high powers, and nothing
allowed to escape the vision which the fraction of a
turn would reveal.

VIII. DRAWING.

In the systematic examination of an object two kinds
of memoranda should be made, descriptions and
drawings. The value of the former is usually conceded,
but that of the latter is often deemed too slight to re-
pay the trouble. The importance of drawing can not,
however, be too strenuously urged, and the difficulty
and tediousness of execution, which will largely dis-
appear with practice, should never be offered as an

excuse for its neglect.

IN TROD UCTION. 1 7

Drawing may represent the object with various
degrees of fidelity. At one extreme is the diagram
(see fig. 1), which only aims to give the relative posi-
tions or sizes of the several parts, or some other feat-
ure. At the other extreme the drawing is as close a
counterpart of the object seen as the person who draws
it is capable of producing (see fig. 3). Whether a par-
ticular object shall be drawn in one way or the other,
or in some intermediate way, must be determined

by the nature of the object and the end to be attained
by the study.

The usual tendency is to make drawings too small ;
they should be large enough to show all parts dis-
tinctly without close scrutiny.

Drawings may usually be satisfactorily made in out-
line, or with very little shading, as in fig. 4 or 6. They
are most easily drawn with a soft pencil on heavy,
unsized and slightly calendered paper, producing the
effect in fig. 3 or 10, but are not permanent ; rubbing
readily defaces them, unless treated to a fine spray of
colorless shellac dissolved in alcohol, which may be
applied with an atomizer, such as is used for perfumery.
Ink drawings are to be preferred fortheirdurability and
distinctness. When ink is used, the main features of the
drawing should first be lightly sketched with a hard
pencil, and the pencil marks erased after the ink is dry.

Drawings in gross anatomy should be the exact size
of the object, or some multiple of it. Record the
amount of linear enlargement by a number placed
at one side of the drawing with an oblique cross
prefixed.

In the directions for laboratory work in gross

1 8 INTRODUCTION".

anatomy the number of drawings has been mostly left
to the discretion of the student.

In minute anatomy the points at which drawings
may most profitably be made are carefully noted. In
many instances, however, it is so difficult to secure a
wholly satisfactory section to show certain structures,
that they should be drawn whenever found in good
condition, without regard to the directions.

Drawings in minute anatomy may be either free-
hand or with camera lucida. In free-hand drawing the
student is especially cautioned against making them
too small, which is a very common fault. In the out-
lines for work it is expected that accurate drawings be
made unless a diagram or diagrammatic drawing is
called for. A diagram (fig. n) shows only a single
special feature, or at most two or three, while a dia-
grammatic drawing (fig. 8 or 10) shows all the chief
features, but does not take note of smaller matters,
such (e. g.) as distinguish the several cells of the same
tissue. When an accurate drawing is to be made, each
individual cell should be drawn as carefully as if it
were the whole object. When an accurate drawing
includes considerable tissue, time may be saved by
indicating the boundaries between the tissues by dot-
ted outlines, and only cells enough filled in to show
the character of the tissues.

In order to draw to scale with the microscope it is
necessary to use a camera lucida. The magnification
is thus determined : place a micrometer on the stage
of the instrument in the same position as an object,
adjust the instrument as for drawing, and laying a
common rule on the drawing paper read off the dis-

IN TROD UCTION, 1 9

tance that the image of one division of the stage
micrometer covers on the rule. If, for instance, a tenth
of a millimeter of the stage micrometer covers five
centimeters (five hundred tenths of a millimeter), any-
drawing under the same adjustment will be magnified
five hundred times. -Always mark the number of
times magnified at the side of the drawing as in gross
anatomy, thus, X 500.

The distance from the drawing-paper to the reflecting
surface of the camera lucida should be about the same
as from the latter to the outer lens of the object glass,
in order that the drawing may properly represent the
magnifying power of the instrument. Ten inches has
been adopted as the standard length of tube.

Trace the image first with a hard pencil, and then
go over it with ink before the object is removed from

the instrument in order to correct any errors made by
the pencil.

It is not an easy matter to draw accurately with the
camera lucida, owing to the difficulty in seeing both
the image and the pencil point distinctly at the same
time. Much depends on the relative amount of light
received by the eye from the instrument and from the
drawing-paper. If the pencil point does not show
clearly, there should be more light on the paper, and

■

if the image is not clear, more on the object.

Invariably accompany each drawing with a full expla-
nation.

IX. BOOKS OF REFERENCE.

It should be the aim of the student to find out all
that he can about the plant in hand with as little assist-

20 INTRODUCTION.

ance as possible or without any. This requires patient
and thorough work. When done, however, and draw-
ings and notes have been fully recorded, it will be
advantageous to compare the work with the published
observations of others, and if any points have been
overlooked or misunderstood, to go over the ground
again.

The following general treatises will be found suita-
ble for preliminary consultation, and when possible
should be constantly at hand on the laboratory shelves :
Gray's Structural Botany, Goodale's Physiological
Botany, Bessey's Botany for High Schools and Col-
leges, Sachs' Text Book, 2nd Eng. edition, Prantl and
Vines' Text Book of Botany, DeBary's Comparative
Anatomy of Phanerogams and Ferns, Strasburger's
Das botanische Practicum, Poulsen and Trelease's
Botanical Micro-Chemistry.

If the student becomes interested in any particular
direction, the references given in the annotations,
together with those to be found in such of the works
just named as may be at hand, will usually give him a
fair start in tracing the literature of the subject, and
becoming acquainted with what has already been ascer-
tained in regard to it. This will indicate wherein

■

present information is defective, and enable him to
direct his labors toward a profitable increase of the
total sum of knowledge.

The references have been preferably to works most
likely to be at the student's command, whenever these
have contained a sufficiently full treatment, this doubt-
less tending more to accomplish the desired object
of interesting the student and leading him on to

IN TROD UCTION. 2 1

independent work, than references in all cases to the
original sources of information. Less accessible works
have often been cited to introduce the student at
once to the most complete treatment of the subject.
A few citations are for the sake of authority.

Many of the memoirs and articles cited in apparently
inaccessible foreign journals and proceedings of socie-
ties may, however, be bought separately of foreign
dealers (R. Friedlander & Sohn, Berlin N. W., Ger-
many, and many others). A very moderate outlay
will thus enable one to consult numerous valuable
writings.

No apology need be offered for referring in an

elementary work to writings in foreign languages, for

unless the student carries his researches outside this
manual he will have no occasion to use them, and if

he does do so he can not go far without being obliged

to use them. It is not often possible in fact to treat a

subject exhaustively in the departments of botany

covered by this handbook without a knowledge of

German and French writings at least.

But if the references given among the annotations

are never used, they will still serve a good purpose in

impressing upon the learner that he is only upon the

threshold of the study, and that the facts which he

seems to be gathering so thoroughly are in most cases

to be found more fully and accurately set forth in the

great storehouse of learning beyond.

GREEN SLIME

Protococcus viridis Ag.

PRELIMINARY.

The plant selected to illustrate the simplest phase'of
vegetable life is found in all parts of the United
States, and even throughout the world. It grows
upon the surface of various objects, being often so
abundant as to give them a conspicuous green color,
especially upon the north side of old fences, barns,
and the trunks of trees, becoming more noticeable
after a few days of damp weather. There are several
other closely related species that may be used, in
fact almost any unicellular green plant will answer,
but this is the one most likely to be gathered. Some

kinds of unicellular plants, like Glceocapsa, have a

sheath or envelope outside the cell proper, not found
in Protococcus, a fact to be borne in mind by the

dent if such plants are used. Pieces of bark or

wood bearing the alga may be kept dry for use, and
will give a fresh appearance when moistened with
water, and even retain vitality for a year or two.

It is quite likely that the plants known under the
name of Protococcus are but early forms of some more
complex algae1, but, however this may be, they serve

1 Bessey, Botany, p. 219 ; Wood, Fresh- Water Algae of North
America, p. 10; Sachs, Text-Book of Botany, 2nd Eng. ed., p. 248;
Cienkowski, Bot. Zeit. 1876, p. 17.

PROTOCOCCUS VIRID1S. *3

quite as well as any to illustrate the simplest kind of
plant life.

To complete the following study it will be necessary
to have pieces of wood bearing the Protococcus ; iodine ;
chlor-iodide of zinc ; and alcohol.

LABORATORY WORK.

GROSS ANATOMY.

Taking either a fresh or dried specimen, notice

1. The color.

2. The evenness with which the plant overspreads the
supporting surface.

Using a lens, notice

3. The pulverulent appearance, as if dusted or sanded
upon the surface.

4. The appreciable thickness reached in some spots,
causing it to separate in scales in the dried specimen.

Mount, and observe

5. The dust-like particles1 into which it separates.

6. The varying size of the particles.

Place a piece of bark with the Protococcus in a small
quantity of alcohol, after an hour or more notice

7. The color imparted to the alcohol by the coloring

matter of the plant, the chlorophyll.*

MINUTE ANATOMY.

Under high power, notice

* Care must be taken not to confound them with air bubbles, which
are often numerous when a dried specimen is used.

8 Some less common forms of unicellular algae are red or purple from
additional coloring matter.

24 GREEN SLIME.

i. The individual cells; either single or associated in
families.

2. The size of the cells ; some small, some several times
larger.

3. The shape ; when free and when in families.

4. The cell contents ; more or less granular, and always
green from the presence of chlorophyll.

5. The colorless cell- wall surrounding each cell.
Press upon the cover-glass with a back and forth move-
ment, and the walls to many of the cells and cell-families
will be ruptured and their contents ejected, when the
wall can be easily studied.

Stain with iodine and notice

6. The brownish-yellow color given the contents of the
cell, showing the presence of protoplasm.

Stain a freshly mounted specimen with dilute chlor-
iodide of zinc, and after an hour or two4 notice

7. The two to several closely packed bodies of definite

outline, usually overlapping, forming the green part

of the cell, the chlorophyll bodies, best seen in the

largest, single, round cells.6

8. The small round body nearly in the center of the cell,
or in recently divided .cells near the partition wall, the

nucleus.

9. Occasionally a clear space between the chlorophyll

bodies and the cell wall, occupied by the protoplasm.
10. Draw a few cells showing chlorophyll bodies and

nuclei.

4 If the cells are properly stained they will usually remain green, but of a
brighter and more bluish hue.

5 There is danger of mistaking delicate partition walls of young cells,
which the reagent has thickened and made visible, for the boundaries of
the chlorophyll bodies.

6 Under higher power yet a central dot to the nucleus, the nucleolus,
may be detected.

PROTOCOCCUS VIRIDIS. 25

1. The cell multiplication : examine various specimens
and trace the successive stages in the division of a
single cell to form a cell family.

2. Illustrate the cell multiplication by drawings.

ANNOTATIONS.

Protococcus is a unicellular plant, for each cell
performs individually the various functions pertaining
to plant life ; and this is true whether the cells remain
single or become associated into small families.

The cell is the unit from which all plants, however
complex, are built up.

The most essential part of the cell is the protoplasm,
a colorless semi-fluid substance, which in this instance
is masked by the green chlorophyll. It is the only
really living, active agent in this, as well as in all other
plants. Its presence here is made manifest by the
characteristic yellowish-brown color given by iodine.

The nucleus (see fig. 9 n) is a special form of the pro-
toplasm to be seen in most plant-cells. As its division
usually precedes that of the cell, it has generally been
regarded as in some way necessary to the latter pro-

. The investigations of Schmitz, Strasburger7 and
others go to show, however, that the two processes
are distinct, and that the nucleus, instead of being
related to cell division, holds an intimate and probably
essential relation to the life of the protoplasm.

The protoplasm takes on another form in the chlor-
ophyll bodies8 (see fig. 9 c). These consist of a proto-

7 Zellbildung und Zelltheilung, p. 371.

8 Cf. Strasburger, Das botanische Practicum, p. 350 ; Schmiu,
Chromatophoren der Algen.

26 GREEN SLIME.

plasmic body containing the green chlorophyll pigment.
The surrounding protoplasm by the aid of the chloro-
phyll is able to convert inorganic into organized matter,
a function wanting in all animals, with the exception
of a few of the lowest, like Hydra and Euglena, and
also wanting in some plants, e. g. fungi and colorless

parasites.

The solid, firm, and nearly colorless cell-wall is a
product of the protoplasm consisting essentially of
cellulose, and serves as a protection to the protoplasm.
The fine granules seen in the protoplasm, are largely
food materials produced by the cell in excess of what
the present needs require.

The multiplication of the plant by cell-division is a
very common method throughout the vegetable king-
dom.9 The nucleus first disappears and two nuclei are
formed in its stead. The protoplasm then divides
itself, keeping a nucleus in each part, and a wall is
formed between. The two cells thus produced soon
attain the size of the original cell, when they in turn
divide into two, but usually by a partition at right
angles to the last, and so on. The cells thus formed

either soon become separated, or retain a mechanical
union.

Another method of multiplication is by the produc-
tion of zoospores.10 The plastic contents of a cell,
either as a whole or divided into several parts, escapes
from the cell wall, each mass pushes out a pair of
delicate protoplasmic filaments or cilia, which moving

9 Cf. Bessey, Botany, p. 36, for a statement of the different methods
by which new cells are formed.

10 Cf. Huxley and Martin, Elementary Biology, p. 12, 15 ; Howes,
Atlas of Elementary Biology, p. 74, pi. xviii.

PROTOCOCCUS VIRIDIS. 27

rapidly back and forth propel the naked protoplasm
through the water. The motion and form give a
strong resemblance to some of the simplest animals,
hence the name of animal-like snores. After a time
they come to rest, draw in the cilia, secrete a cell-wall,
and become ordinary Protococcus cells. Sometimes
the protoplasm does not free itself from the cell wall,
but contracts somewhat, the cilia are protruded through

the wall and the mass propelled as just stated. The
production of zoospores at a specified time, as for a
class demonstration, is attended with so much uncer-
tainty that their study has been omitted from the
laboratory work. This method of asexual multiplica-
tion will be studied later under more favorable condi-
tions in Cystopus."

11 At p. 47.

DARK GREEN SCUM.

Oscillaria tenuis Ag

PRELIMINARY.

The color of Oscillaria, almost any species of which
may be used, is generally sufficient to enable one to
distinguish it at sight. Its dark blue-green is in
marked contrast with the yellow-green of most other
plants which form scums. It is very common on
stagnant water, often forming patches of scum thirty
centimeters (a foot) or more in diameter, which becom-
ing loaded with dust finally sink to the bottom. It is
also very common about watering troughs, along street
gutters, at the outlet of drains, on wet rocks/ giving
them a slippery surface, in the greenhouse, and especi-
ally in water containing a small amount of garbage.
It can usually be grown indefinitely in an open jar, by
supplying the water as it evaporates, or with less
trouble, when once established, in an unstoppered bottle,
in which a small twig or flower stem of some sort is
inserted to provide nutriment. The plants are often
to be found in winter in as good condition as in sum-
mer. The study should be made upon growing plants
when possible, but specimens dried on paper or mica
will serve quite as well, except to show the oscillating
movements, which are characteristic of the group to
which Oscillaria belongs.

OSCILLARIA TENUIS. 29

Only the following material is necessary for the
study: fresh plants, or in their absence dried speci-
mens ; a dried mass half as large as a pea ; and alco-
hol.

LABORATORY WORK.

GROSS ANATOMY.

1. Examine a small mass of the living plant which has
been allowed to remain undisturbed for several hours
in a watch-glass of water ; notice

a. The deep blue-green color.

b. The hair-like unbranched filaments^ radiating

from the central mass.

2. Sketch the plant as it appears in the watch-glass.

3. Mount a fragment and observe the uniform diameter
and appearance of the filaments.

Pulverize a mass of the plant that has been thoroughly
dried, place in a test-tube or vial with nearly twice
the bulk of water, and after ten to twenty-four hours
notice

4. The color of the solution when seen by transmitted
light and the very different color by reflected light,
indicating the presence of phycocyanine.

Pour off the supernatant water, add the same amount of

alcohol instead, and after an, hour or more notice

5. The yellow-green color imparted by the chloro-
phyll.

MINUTE ANATOMY.

A. GENERAL CHARACTERS. Under a low 'power
notice

1. The color.

SO DARK GREEN SCUM.

2. The numerous filaments of uniform diameter, destitute
of branches.

3. Study the movements.

B. THE INDIVIDUAL FILAMENT. Under high
power, notice

i. The structure in detail, as follows :

a. The rounded extremities of uninjured filaments.

b. The outline of an uninjured apex, whether attenu-
ated or not, and whether bent to one side or
straight.

c. The delicate lines of the partition walls crossing

the filament and dividing it into very small
cells.

d. The comparative length and breadth of the ,

cells.

e. The granular contents, and their distribution in

the cell.1

The delicate colorless sheath to be seen extending
beyond the green cells at some torn end of a fila-
ment, and on which may sometimes be detected
transverse lines indicating the former position of
the end walls of the cells.

2. The turgidity of the cells: notice that

a. The

njured filament are

plane, while

b. The last cell of an injured filament is bulged out-
ward, making the outer transverse wall convex,
the pressure from within not being counterbal-
anced from without.

3. Draw one or more filaments.

1 11 1 iiwimiim ■■ ■ —— 1 m "~"~ — ■ ■ -

In some species the granules are collected along the partition walls.

OSCILLARIA TENUIS. 31

ANNOTATIONS.

If the structure of Oscillaria be carefully compared
with that of Protococcus more points of resemblance
will be found than appear at first sight. New cells are
formed by the process of division, as in Protococcus,
but the partition walls are always parallel and in one
direction, which disposes the cell families in filaments.
The individual cells have thin walls, the office of pro-
tection being relegated to the sheath. The sheath,
which is formed from the outside walls of the cells by
a modification of the outer portion, is a structure that is
mostly confined to certain groups of the lower plants,
although it has some analogies with the cuticle of the
higher plants. The protoplasm is homogeneous, and
not differentiated into chlorophyll bodies and nucleus
as in Protococcus ; chlorophyll is, however, present,
evenly distributed through the protoplasm, but no
nucleus has yet been discovered. The study of the pro-
toplasm and chlorophyll is much obscured by the pres-
ence of the peculiar coloring matter, phycocyanine,
characteristic of the Cyanopkycece to which Oscillaria
belongs. It is this that gives the deep blue-green color
to the plants, enabling one to distinguish them at sight.
It is insoluble in alcohol, but soluble in water when the
plants are dead, while chlorophyll is soluble in alcohol,
but not in water; hence, digesting the dead plants with
water removes the phycocyanine, and digesting with
alcohol removes the chlorophyll.3 This blue color is
often seen on the sides of vessels in which Oscillaria
has remained so long as to die, and also staining the

' Cf. Sachs, Text-book of Botany, 2nd Eng. ed., p. 246, 766.

32 . DARK GREEN SCUM.

herbarium sheets on which specimens have been
dried.

The cells are assisted in keeping together by the
investing sheath, into which they are packed like a roll
of lozenges in their case. This structure, togetherwith
the community of action exhibited in producing the
peculiar oscillating and nutating movements, makes it
evident that the cells of each filament have a certain
dependence upon each other, although at the same
time each is capable of independent existence. It may
be that the smallness of the cells and the thinness of
their walls is in some way correlated to this unity of
function. It is not yet definitely known how the move-
ments in Oscillaria are produced.3

Turgidity is a characteristic of living cells. It is the
means by which the soft parts of plants are enabled to
keep their form, and otherwise to serve their purpose.
It is brought about by the strong imbibition power of
the protoplasm, causing water to be taken up until
a considerable internal pressure is created.*

3 Engelmann has discussed several theories, and suggested that the
movements are brought about by vibratile thread-like extensions of the
protoplasm through the cell walls. Bot. Zeit. 1879, p, 49 According
to Hansgirg it is due to an osmotic action of the protoplasm. Bot.
Zeit. 1883, p. 831.

4 Cf. Bessey, Botany, p. 166.

COMMON POND SCUM

Spirogyra quinina Kutz.

PRELIMINARY.

The members of this genus are abundant in stagnant
water everywhere, forming bright yellow-green scums of
great extent, sometimes diffused beneath the surface, or
in running water attached to stones. They may be read-
ily distinguished from all other scum-producing plants,
except from a few of their close allies, in having a slip-
pery feel, and being composed of long unbranched fila-
ments, which string out like wet hair when withdrawn
from the water. The allied kinds, which can not be
separated by this simple test, will at once be distin-
guished when placed under the microscope by possess-
ing no spiral chlorophyll bands as in Spirogyra. When
growing vigorously the masses of Spirogyra are an
intense light green ; when beginning to fruit they turn
brown, and look very uninviting ; but as the characters
which distinguish the species are largely drawn from
the fruiting condition, the collector soon learns to
regard these unsightly objects with favor.

The vegetative condition may be found at any time
during the warmer portion of the year. The fruiting
condition occurs from early spring to June and July,
and sparingly during the remainder of the warm season.

The species usually grow intermixed, and almost any

34 COMMON POND SCUM.

gathering will answer for the present study, as 5.
longata Vauch., 5. majuscula Kiitz., and similar kinds
have been kept in mind as well as S. quinina in drawing
up the outline for laboratory work.

Spirogyra may be grown in the laboratory, and the
vegetative condition kept always at hand, by using a
rather deep vessel with opaque sides, and occasionally
dropping in a small piece of peat which has been
thoroughly boiled and afterward saturated with the
following nutritive solution : 1,000 cc. of water, i gm.
potassic nitrate, .5 gm. sodic chloride, .5 gm. calcic sul-
phate, .5 gm. magnesic sulphate, and .5 gm. finely pul-
verized calcic phosphate.1 The last, for which burned

bone may be used, is only sparingly soluble. If

ning water can be conducted through the jar contain-
ing Spirogyra, so that the water in it may be slowly
changed, the peat and nutritive solution can be dis-
pensed with. The fruiting plant may be preserved
in fair condition for study in a fluid of equal parts of
glycerine and alcohol.

The requisites for study are thrifty growing plants ;
fruiting plants, fresh if possible ; alcohol ; glycerine ;
and iodine.

LABORATORY WORK.

GROSS ANATOMY.

A. GENERAL CHARACTERS. Notice
1. The yellow-green color as seen in mass.

1 Sachs, Vorlesungen uber Pflanzen-Physiologie, p. 342.

SPIROGYRA QUI NINA. 35

2. The slippery feel, when the plant is taken between the
fingers.

Float a small amount of material in water over a white
surface, and observe

3. The fine unbranched filaments of which it is com-
posed.

4. Their uniform diameter.

5. Their length.

Place some in alcohol, and after some time notice

6. The color imparted to the alcohol by the chlorophyll.

B. Mount a few filaments, and notice the single row of
alternating light and dark dots, indicating the single row
of cells. This can not be seen in all specimens.

C. THE FRUITING PLANT. Mount a few filaments
from a fruiting mass, having them well separated on the

slide, and search for

1. Paired conjugating filaments, some cells of which are

empty, some with dark colored dots, the zygospores,
and a few often remaining unchanged from the vege-
tative condition. a

MINUTE ANATOMY.

A. GENERAL CHARACTERS. Under low power

notice

1. The indefinite length ; if traced to the end, the fila-
ment will probably be found broken.

5 The presence of small particles of dirt and other debris makes it diffi-
cult to distinguish the zygospores and conjugating filaments with cer-
tainty, and it is always best to verify the observation with the compound
microscope, if possible.

36 COMMON POND SCUM.

2. The uniform diameter.

3. The cell contents ; colorless, except the conspicuous
green chlorophyll bands.

B. THE INDIVIDUAL FILAMENT. Using a high
power, notice

1. The shape of the cells.

2. Their relative length and breadth.

3. The cell wall :

a. The lateral walls j parallel and without mark

of any sort.

b. The end walls ; at right angles to the longituc

axis, and plain (unless slightly nodulated or
infolded, which occurs in a few species).

4. The absence of any visible sheath, although the pres-
ence of at least a thin one has been demonstrated by
the slippery feel.

5. The cell contents.

a. The chlorophyll bands, taking a spiral course from

one end of the cell to the other, passing near the
periphery. Note
i. The number in each cell.3

3'When a cell is crowded with chlorophyll, the following method may
be used to advantage in determining the number of bands : count the
number appearing to cross the band aby between the point a> the upper
profile view, and the point b, the lower profile view ; this number plus

one will be the
number re-
quired. The
diagram shows
a cell with four
bands of chlo-
rophyll.— From
Bot. Gazette, ix.,

SPIROGYRA QUININA. 37

ii. The number of turns of the spiral,
iii. The surface, the crenulated and wrinkled

margin, and the turned up edges of the

band forming a more or less flattened V m
optical section. To obtain a complete con-
ception of these particulars, first focus upon
the peripheral surface of the band, i.e., upon
the upper (outer) surface of the part nearest
the eye, then focus upon the axial (inner)
surface, and finally examine the profile of the
band seen on the right or left of the cell,
iv. The nodules at varying distances along the

median line of the band. Stain with iodine
and note

a. An outer ring which is more deeply

colored, starch,4 and

A central light spot, pyrenoid. Both are
best seen when but faintly colored,
v. The yellowish brown color finally imparted to

the chlorophyll band.
b. The feeble brownish color given to the remainder

of the contents of the cells, deeper along the
periphery.

Run under glycerine on the same slide, and note

c. The contraction of the colored protoplasmic part,

and its separation from the cell wall.

d. In unstained cells presenting the least obstruction

from the chlorophyll bands, search for a colorless
irregular body with radiating arms, near the center
of the cell, the nucleus. This is difficult to demon-
strate in some species, but easily seen in others.

4 Unless the plants have been in sunlight the preceding part of the day
the test for starch may not be fully successful.

3 8 COMMON POND SCUM.

e. The rounded, usually much brighter body im-
bedded in the nucleus, and occupying a consid-
erable part of it, the nucleolus.
Draw one or more cells showing all parts noticed.

6. The turgidity of the cells, shown by the considerable
convexity of the last end wall of a broken filament,
which is repeated in lessening degree by the walls of
successive cells until a point is reached where the pres-
sure on opposite sides is equal, and the wall remains
plane. Illustrate with a sketch.

C. THE FRUITING PLANT. Under low power, notice
i. The filaments lying side by side in pairs, held together

by conjugating tubes.

2. The irregular outline of the filaments, caused by the
uneven lateral expansion.

3. The varying character of the contents of the cells : some
with distinct bands of chlorophyll ; some with a con-
fused green mass ; some with green or brown rounded
bodies of definite shape, the zygospores ; some empty.

Under high power, notice

4. The general shape of the cells as influenced by the cell
contents.

5. The conjugating tube : note

a. The enlargement at the middle, where an indenta-
tion marks the line of union of the two originally
separate portions.

b. In some cells which have not yet conjugated, a

greater or less protuberance on the side next the
accompanying filament ; the beginning of a con-
jugating tube.

6. The cell contents.

SPIROGYRA QUIN1NA. 39

a. By studying various specimens, trace the changes

from the vegetative condition, through the several
stages of disintegration of the chlorophyll band
and contraction of the protoplasm to the forma-
tion of a rounded uniformly greenish-brown mass ;
noticing at the same time, that this change takes
place side by side with the formation of the conju-
gating tube. In general all the stages are easily

found.

b. Where the conjugating tube is fully formed, note

that one cell is empty, and the connected cell con-
tains a single mass, the spore produced by the
conjugation.

7. The mature zygospore : note

a. The shape and color.

b. The contents.

c. The wall of greater or less thickness, usually

resolvable into two or more layers of different

colors.

8. Make drawings to illustrate the parts and changes of
the fruiting filaments.

ANNOTATIONS.

In the form and manner of growth of Spirogyra, we
meet with no features not seen in Oscillaria or Proto-
coccus, except the arrangement of the protoplasm and
chlorophyll bodies. The filaments are built on the
plan of Oscillaria, with the cells larger, and the sheath
so much reduced that it can be demonstrated only with
difficulty. In some species of the closely related genus
Zygnema, however, the sheath is readily discernible.
The increase in the number of cells is effected in the

40 COMMON POND SCUM.

same manner as in Oscillaria, i. e. by the division of
the cell into halves by a transverse partition always in the
same direction, with subsequent expansion of the new
cells.

The disposition of the protoplasm shows a marked
advancement over the lower plants. Instead of being
diffused evenly through the cell, it forms a layer lining
the cell-wall, known to older botanists as the primor-
dial utricle,6 while it only partly occupies the central
portion of the cell. The remaining space is filled by
the cell-sap, which consists of water holding various
substances in solution. The nucleus and nucleolus,
particularly the latter, are remarkably large. In the
chlorophyll band we have a unique feature ; for while
it is common to have the chlorophyll separated in well
defined bodies, it is only in Spirogyra and its close rela-
tives that it assumes such peculiar and beautiful shapes.

The presence of starch granules in the chlorophyll
bodies is a very significant fact in the physiological
study of plants. They, or very similar substances,
are the first products of assimilation,6 being the material
from which the elaborate frame-work of the plant is
eventually constructed. Usually the starch when first
formed is scattered irregularly through the chlorophyll
bodies; in Spirogyra, however, the principal part is
collected in a layer of granules about definite centers
forming hollow spheres. Within these spheres is a
highly refractive protoplasmic body, the pyrenoid.

5 So named by H. v. Mohl, Bot. Zeit., 1844, p. 273 ; The Vegetable
Cell, p. 36.

6 Cf. Sachs, Handbuch d. Exper.-Phys. , p. 307 ; Textbook of Botany,
2nd Eng. ed., p. 703 ; Bessey, Botany, p. 178.

SPIROGYRA QUININA. 41

The starch is imbedded in the chlorophyll bodies, and
is quite distinct from the pyrenoid, although the con-
stancy in the relative position of the two would indi-
cate some connecting influence. The pyrenoids have
been long known and variously interpreted,7 but the
recent careful studies of Schmitz8 show that they are
quite analogous to nucleoli, especially in chemical
constitution and mode of multiplication. They are
only found in some of the algae and in a few higher
plants.

It is when we examine the fruiting of Spirogyra,
that its great advancement beyond the simple forms
of the protophytes becomes apparent. We meet at
once with a true sexual process, which although very
simple is yet clearly defined and easily traced. This
process, as indeed in all other instances however mod-
ified, consists essentially of the intimate union of the
protoplasm (especially of the nucleus9) of one cell with
that of another, which after a longer or shorter period
results in the production of a new individual. Usually
in higher groups there is a marked difference in size,
and we may conclude in other less apparent respects,
between the protoplasm which is fertilized, the female
element, and the protoplasm which fertilizes it, the
male element. In Spirogyra a slight difference between
the two elements, especially in size, has been pointed
out by DeBary,10 Wittrock,11 and more fully by Ben-

7 Hofmeister in Die Lehre von der Pflanzenzelle (1867), p. 370, calls
them vacuoles.

8 Die Chromatophoren der Algen (1882), p. 37 etseq. ; Quart. Jour.
Mien Sci. , xxiv, p. 246.

9 Cf. Strasburger, Neue Untersuchungen, p. 80.
10Untersuchungen liber die Familie der Conjugaten, 1858, p. 4.
"Quart. Jour. Micr. Sci., 1873, p. 123.

4 2 COMMON P OND SC UM.

nett.19 According to Bessey," however, we should
consider this case the simplest kind of sexuality, in
which there is as yet no differentiation into proper
male and female. For the further discussion of sexu-
ality in plants, the student is referred to the writings
of Pringsheim," Sachs," Ward,16 Strasburger,17 and
others.

The two plants previously examined may be found
in any month of the year, but the one now under
examination dies, and entirely disappears from sight
by the time winter has fairly set in. It is reproduced
the coming spring by the germination of the zygospores,
which lie at the bottom of the water during the
winter. These resting spores are admirably fitted for
spanning this unfavorable season for vegetation. As a
rule they require a long period of rest before reaching
the germinating condition, so that while they are
formed in the earlier part of the warm season, it is
usually not till the following spring that they show a
disposition to grow ; they are dense and heavy, and
therefore sink to the bottom as soon as set free by the
decomposition of the filaments in which they grew ;
and lastly, their thick double or triple covering serves
as an ample protection to the living protoplasm with-
in.

19 Jour. Linn. Soc., xx (1884), p. 430; Amer. Nat., xvii (1884), p. 421.

13 Amer. Nat., xix (1885), p. 995.

14 Monatsber. d. k. Akad. der Wiss. in Berlin, 1869.
16 Textbook of Botany, 2nd Eng. ed., p. 986.

16 Quart. Jour. Micr. Sci., 1884, p. 262.
» Op. cit.

WHITE RUST.

Cystopus candidus Lev.

PRELIMINARY.

THIS isa very common parasitic fungus, forming white
patches on the surface of the leaves, stems and flowers
of many cruciferous plants, such as various species of
Capsella, Sisymbrium, Lcpidium, Nasturtium, Sinapis,
and Raphamis. It is especially abundant upon Cap-
sella or shepherd's purse,1 from early spring till late
in the fall, whitening and distorting the stems, leaves
and flowers. Yet, notwithstanding such luxuriant
growth, the sexual condition with resting spores is not
abundantly found on this host, but is, however,
produced in great luxuriance inside the flowers and
flowering branches of radish (Rapha?ius), causing
them to become enormously enlarged, sometimes even
two to five centimeters (one or two inches) across (see

fig- 3);

It is possible, with patience and care, to make out
the parts without the use of chlor-iodide of zinc, but it
affords so much assistance that it ought to be used if
obtainable.

The requisites for the following study are branches

1 For a description of shepherd's purse see p. 222.

44 WHITE RUST.

of Capsella bearing the rust, dried or fresh ; the same,
together with some young terminal portions of affected
branches, preserved in alcohol ; the swollen flowers of
radish or Capsella taken when not too young, but still
tender and brittle, preserved in alcohol ; freshly gath-
ered branches of rusted Capsella, or some which have
not been gathered more than twenty-four hours and
kept in a moist bell jar; chlor-iodide of zinc; potassic
hydrate ; and iodine.

LABORATORY WORK.

GROSS ANATOMY.

i. The vegetative body of the plant consists of delicate
transparent threads, ramifying through the tissues of
the host on which it grows, and can not be detected
without the aid of the compound microscope.

2. The sori : in a fresh or dried specimen notice

a. The white blister-like pustules on the surface of

the host, sori ; shape and extent.

b. The thin external membrane, at first entire, then

becoming ruptured in the middle.

c. The white powdery spores, conidia, which drop

out upon jarring, if the specimen is dry.

3. Mount a section from an alcoholic specimen of radish

flower containing Cystopus, stain with chlor-iodide of

zinc, and notice

a. The numerous dots scattered through the tissue

of the radish, the oospores or resting spores. The
staining shows them as red dots lying in a blue or
yellow ground tissue.

CYSTOPUX CANDID OS. 45

MINUTE ANATOMY.

Mount a transverse section of an alcoholic specimen of a
stem or leaf bearing Cystopus, and under low power
notice

i. A layer of short vertical filaments, conidiophores,*
together forming the hymenium, which appear to arise
from the tissues of the host and bear on their free
extremities

2. Chains of rounded conidia, now mostly detached.

The vegetative portion of the plant, consisting of branch-
ing filaments pervading the tissues of the host, can rarely
be made out even after staining, without specially skillful
manipulation.

3. The everted membrane formed from the surface cells of
the host, formerly covering the sorus.

4. Draw.

Under high power notice

5. The conidia : exact shape, wall and contents.

6. The delicate neck ox pedicel supporting each conidium
before becoming detached.

7. Draw a conidiophore with its conidia.

Take a piece of the host bearing conidia and boil for a
minute or two in potassic hydrate ; remove a portion to the
slide, tease apart thoroughly with needles, and stain with
chlor-iodide of zinc. Notice

8. Much branched, often matted filaments, mycelium,
pulled out from the tissues of the host.

Cf. fig. 8.

46 WHITE RUST.

a. The irregular thickness of the mycelial filaments,

or hyphffi.8

b. The absence of transverse partition walls.

c. Draw a few hyphae.

9. The groups of conidiophores.

a. The manner in which the conidiophores arise

from the vegetative hyphae.

b. The successive degrees of abstriction of the

conidiophores resulting in the formation of the
spores.

c. Draw a group of conidiophores with the attached

hyphae.

Prepare a slide as before, using the immature terminal
part of the branch bearing the Cystopus, preferably a
flowering branch ; search among the untorn tissues of the

youngest organs, particularly in the pedicels of the young
buds, for the extremities of the advancing hyphae.4
After noting the more direct course of the hyphae, and the
fewer branches, observe

10. Very small globular bodies lying along the side of the

hyphae, haustoria or sucking organs.6 They usually
appear brighter than the hyphae, and are quite abund-
ant. If the illumination is sufficiently strong, observe

a. The very delicate stalks by which the haustoria

are connected with the hyphae.

b. Draw some hyphae with haustoria.

zHypha is the name applied to a single filament, while mycelium is a col-
lective term for a number of hyphae.

4 If properly stained there will be no difficulty in distinguishing the
mycelium from the tissues of the host.

It is difficult to demonstrate these without proper staining.

CY STOP US CANDID US. 47

Dust some conidia from a fresh growing plant* upon a
slide and mount with water ;7 in about an hour, notice

11. The small protuberance formed on one side of some of

the conidia, which opens and permits the escape of
the protoplasm in the form of several motile bodies,

zoospores.

a. The shape of the zoospores, and the pair of

bright spots in each.

b. Study the movement.

c. Notice the pair of delicate vibratile cilia, by

means of which the movements are effected. Stain
with iodine, and the cilia can be seen more easily.
Note their length.

d. The color imparted to the zoospore and its cilia by

the iodine.

e. Draw some zoospores, and also one or two conidia

which have not discharged zoospores, and one or
two empty ones.

12. The sexual reproduction. Stain a section of an alco-
holic specimen of radish flower containing oospores
with chlor-iodide of zinc, and notice

a. The numerous globular bodies, stained wine-red,

lying in the tissues of the radish, oogonia.

b. Accompanying them, and stained the same, smaller

rounded bodies, antheridia.

c. In some of the oogonia, a globular mass of

granular protoplasm, not completely filling the

oogonium, the oosphere.

d. A slender tube passing from the antheridium to

6 The conidia will germinate if sown at any time of day, provided the
specimens are fresh, but will do so more readily when sown in the morn-
ing from plants which have remained over night under a moist bell jar.

7 Care must be taken that the water does not evaporate, and to guard
against this it is best to use a slide having a shallow cell.

48 WHITE RUST.

the oosphere, the fertilizing tube ; very difficult

to demonstrate. Draw.
e. In older oogonia, more opaque roughened bodies

the oospores, formed from the oospheres. Note
i. The flexuous ridges on the exterior.

ii. The contents, in spores not too mature.
Draw some oogonia and accompanying antheridia
showing different stages of development of the
oosphere and oospore.
Tease out some tissue containing oospores, which has
been boiled in potassic hydrate, stain lightly or not at all,
and notice

g. The manner in which the oogonia and antheridia arise

from the vegetative hyphae. Draw a few examples.
h. The rather strong, pointed beak sometimes to be

seen on one side the antheridium, the fertilizing tube
which has been pulled out of an. oogonium. Draw.

ANNOTATIONS.

In Cystopus we have a much simplified condition of
an advanced type of development. The higher devel-
opment is shown in its sexual reproductive apparatus,
the sexual elements being quite dissimilar in size and
in behavior. The larger (female) element, the oogo-
nium, receives the protoplasm of the smaller (male)
element, the antheridium, the former remaining in a
passive state, while the antheridium is the active agent
in securing the union. This is the essential plan for
all higher plants, as well as for the group to which
Cystopus belongs, the Oophyta.8 The transfer of the

8 The terms Zygophyta, Oophyta and Carpophyta are used for the
three great groups, of lower plants, in accordance with the suggestion of
Prof. C. E. Bessey in the American Naturalist, xvi (1882), p. 46,
and first introduced in his Essentials of Botany, 1884.

CYSTOPUS CAN DID US. 49

protoplasm by means of a fertilizing tube, and the
subsequent formation of a thick-walled resting spore is
very similar to what takes place in Spirogyra. In both
cases the spore clothes itself with a thin inner wall,
very difficult to see clearly, and an outer, thick pro-
tective wall. In Cystopus this outer wall is sculptured
in a manner characteristic of the species. The oospores
thus formed remain over winter ; the tissues in which
they lie become disintegrated ; they are distributed by
rain and wind, and finally germinate.

Next to the mode of sexual reproduction, the most
interesting feature about the plant under consideration
is its habit of life and the adaptations which have been
induced thereby. It is throughout its existence a
complete parasite, growing and feeding upon plants of
a very high degree of organization. Being no longer
required to elaborate food for itself, finding it always
at hand and of superior quality, it possesses no chlo-
rophyll bodies by which it might assimilate its own
food, and is therefore quite colorless. As it grows,
it sends its branching filaments ramifying throughout
all the softer tissues of the host. They do not
penetrate the cells, however, but push about between
them, and in order to extract the nourishing fluids
readily, especially in the newest portions where rapid
growth is taking place, send out sucking tubes or
haustoria, which penetrating the adjacent cells expand
into minute absorbing bulbs.

The means of distribution which the plant possesses
in its oospores is rather limited, being inferior to that
of Spirogyra ; and when once established in a host it
is debarred from all further locomotion, such as the

50 WHITE RUST.

moving water imparts to the spores of Spirogyra. In
order to secure certain and extensive distribution, there-
fore, and to provide for a succession of crops through the
growing season, it produces conidia or summer spores
in the greatest profusion, which being light and dry
are easily blown about by the wind, and are ready to
germinate at once. The thin wall and active pro-
toplasm of the conidia, from which they derive this
advantage, render them at the same time short lived,
so that if a conidium does not find favorable con-
ditions for growth within a few hours after reaching
maturity, it perishes. The conidia germinate in water,
and with best results in a film of water, such as is
formed by heavy dew. To still further promote dis-
tribution, each conidium breaks up into several active
zoospores, which, after moving about for fifteen min-
utes or so and finally coming to rest, put out a myce-
lial tube that penetrates the host, and forms a new
plant. The zoospores, except in being colorless like
the parent, remind us of those of Protococcus, serving
the same purpose of distribution and reproduction.

The absence of septa, except for the separation of
the antheridia, oogonia and conidia, making the vege-
tative portion a continuous cavity, is a character
shared with many other members of the Oophyta, both
colorless and green forms, and with some of the molds
belonging to the Zygophyta.

The student has doubtless been struck with the
rarity of the cases in which he could detect a fertilizing

tube, even where the antheridium appeared to lie in
the proper plane. There is doubtless a reason for this

aside from the mere difficulty of manipulation, which

CYST OPUS CANDID US. 51

is to be sought in the nature of the parasitism exhibited
by Cystopus. Whatever may be the full significance
of sexuality, many facts point to the belief that it is
an expedient for the reinvigoration of the exhausted
energies of the plant.9 Cystopus is intimately asso-
ciated with a plant immensely above it in the scale of
development and of a correspondingly higher poten-
tiality. Its vigor is in direct ratio to that of its host,
which latter far exceeds the requirements of the simple
parasite. The energy which the parasite receives
from its host may take the place to some extent of that
usually obtained through the sexual process. It there-
fore seems justifiable to believe that while the anther-
idia are in most cases formed, the fertilizing tube is
often either not present or functionless, i. e. that we
have the production of oospores without the aid of the
male element, a method known as parthenogenesis,10 a
difficult matter to establish by observation. This view
is rendered more probable by the fact that it is the
customary mode of reproduction in some of the closely
allied Saprolegniae " which are mostly parasitic for at
least a part of their life upon insects, a still more
highly organized food than that obtained by Cystopus
and its immediate allies.

9 Ward, Quart. Jour. Micr. Sci. xxiv, (1884), p. 303; Bot. Gaz. ix,
p. 146.

10 Sachs, Text-book of Botany, 2nd Eng. ed., p. 902 ; Ward, 1. c, p.
307.

nPringsheim in Jahrb. f. Wiss. Bot., ix ; DeBary, Beitrage zur
Morph. u. Phys. der Pilze, 4te Reihe, p. 73 ; Sachs, 1. c, p. 275,

THE LILAC MILDEW

Microsphcera Friesii Lev.

PRELIMINARY.

The mildew on lilac is extremely common in the
United States, making the upper surface of the leaves
look white and moldy from midsummer on. The
first stage at which the fungus is ready to gather is
when it appears powdery, which is usually in June or
July, the earlier collections being the best. The next
gathering should be made in the early part of Septem-
ber, and another just before the leaves fall. As the
leaves bearing the fungus are gathered, lay them in a
book or plant-press to dry. If it is possible to examine
the first stage with fresh material it will prove more
satisfactory, but for the remainder dried material will
answer quite as well.

The required material consists of dried lilac leaves
bearing the fungus, gathered in midsummer and
autumn ; and potassic hydrate.

LABORATORY WORK.

GROSS ANATOMY.

A. GENERAL CHARACTERS. Notice

i. The distribution of the fungus over the surface of the
leaf.

MICROSPH&RA FRIESII. $3

2. The color.

B. THE CONIDIA. Notice

i. The pulverulent appearance on the leaves first gathered,
caused by the abundant conidia.

C. THE FRUIT. Notice

i. The black dots on leaves gathered later in the season,

the spore-fruits or perithelia.

2. Associated with the black dots, other yellow ones, the

immature fruits.

MINUTE ANATOMY.

A. THE MYCELIUM. Scrape the fungus from the sur-
face of a leaf gathered in early summer, having first
moistened it with potassic hydrate if the specimen is a
dried one, and under high power notice

i. The colorless filaments of the mycelium.
• a. The branching.

b. The irregular diameter.

c. The rarity' of partition walls.

2. Small lateral expansions of the filaments, haustoria,
somewhat like irregularly indented disks with very
short thick stalks. Generally difficult to find.

3. Draw.

B. THE CONIDIA. Prepare a slide as before from a pul-
verulent surface, and notice

1. The abundant conidia, separated and free, owing to the
manipulation.

a. Their shape and color.

b. The cell -wall and contents.

2. The conidia-bearing branches, or conidiophores, which
leave the mycelial filaments at right angles, and are
provided with cross partitions at regular intervals, and

54 ULAC MTLDF.W.

to which may yet be attached some fully formed
spores.

3. Draw some conidiophores and conidia.

C. THE PERITHECIA. Prepare a slide as before with

mature fruit, and notice

1. The shape and color.

2. The reticulations of the surface due to the cellular
structure.

c .

3. The appendages extending out from the sides. Note

a. The number.

b. The color.

The length compared with the diameter of the
perithecium.

d. The cross partitions, if any.

e. The manner of branching, and the number of times

in each.

■

4. Draw a perithecium with its appendages.

Crush the perithecia while watching them through the
instrument, by pressing on the cover-glass with a dis-
secting needle, and notice

5. The escape of sacs containing spores, asci. Note

a. The number from each perithecium.

b. The general shape.

c. The short pedicel or beak by which they were

attached.

d. The thin part of the wall at the apex, not to be

seen in every case.

e. The number of spores (ascospores) in each ; their

shape.
Draw an ascus with its spores.

MICROSPIf&RA FRIESII. 55

6. Examine younger and younger perithecia to as early a
stage as possible. Draw.

D. The very simple ORGANS OF FERTILIZATION,
the beginning of the perithecia, can rarely be found1 ; if
seen, notice

a. The larger axial cell, the carpogonium.

b. The smaller lateral cell, applied closely to the car-
pogonium, the antheridium.

c. Draw.

ANNOTATIONS.

The group of Carpophyta to which Microsphaera
belongs, a very large one, is characterized by having a
special covering for the spores, developed as a result of
fertilization. Except in some of the higher forms, the
fertilization takes place much as in the Oophyta, but the
subsequent development is very different, for an out-
growth of branches from the portion immediately
below the organs of fertilization at once arises which
eventually envelops the forming spores and develops
into the body of the fruit.

It is altogether likely that Microsphaera has reached
an advanced parthenogenetic stage, i. e. the fruits are
largely produced without the transfer of protoplasm
from the antheridium to the carpogonium, which consti-
tutes fertilization. On this account some other plants
better illustrate the fertilization and the early growth of
the fruits than the one used ; the student is advised
to examine these features, if possible, in Nemalion, one

1 To get some idea of their shape, examine figs. 188 and 189 in Bessey's
Botany, p. 280-1.

LI LA C MILDE W.

of the marine algae, or Batrackospermutn, one of the
fresh-water algae.

The comparison of Microsphaera with Cystopus is
very instructive in showing how practically the same
ends have been reached by widely different plants.
Both are parasitic, the one living inside the host, the
other upon its surface, both deriving nourishment by
means of haustoria, in addition to what is absorbed
directly through the walls of the filaments. It is some-
what doubtful, however, if the haustoria of Micro-
sphaera pierce the cells of its host, although those of
some closely related species are thought to do so.2
Both bear aerial asexual spores, which are formed
by successive abstrictions from vertical mycelial
threads, the main difference being that in Cys-
topus these must break through the surface tis-
sue of the host, and are therefore required to grow in
groups in order to exert the necessary force, while in
the superficial Microsphaera they are single, and evenly
distributed. The conidia of Cystopus germinate by
formation of zoospores, while those of Microsphaera
grow a mycelial filament at once, a difference due to
some obscure cause. Both plants form resting spores,
but in Cystopus the protective covering is the thick-
ened wall of the spore, in Microsphaera it is a specially
developed shell, inclosing a number of spores in sacs.

There is not much known of the manner in which
these fruits pass the winter and give rise in the spring

to another growth of mildew.3 It is plain from

3 Cf. Bessey, Botany, p. 279.

3 Wolff has studied the germination of the ascospores in Erysiph
graminis. Bot. Zeit. 1874, p. 183,

MICROSPHsERA FRIESII. $7

the structure, however, that the spores escape from the

sacs through the thin spot at their apex, but not so

evident how they escape from the shell of the fruit

and reach the host plant. The appendages we

may suppose are of some service in distributing the
fruits.

COMMON LIVERWORT

Marchantia polymorpha L.

PRELIMINARY.

This plant is common throughout America and
Europe. It grows among grass, over wet soil or
rocks, in dryer spots along walls and fences, and occa-
sionally in more exposed situations, but is most luxu-
riant in damp shady places. The vegetative part con-
sists of flat, green, leaf-like stems, twelve millimeters
(half inch) or so wide and five to eight centimeters
(two or three inches) long, appressed to the ground,
held down by numerous silky hairs on the under side,
and much branched, usually forming extended mats.

There are two sorts of reproductive branches which
occur on separate plants. These branches (see fig. 2)
are slender stalks about an inch high, bearing flat disk-
like heads a quarter of an inch or more across — the
male with scallops, the female with finger-shaped rays.
The two forms sometimes grow at the same spot or
locality, but quite as often entirely apart from each
other. Besides these organs there are often small
sessile cups (cupules) on the upper surface of the stems,
containing green grains.

If either cupules or reproductive branches are present,

MARCHANTIA POL YMORPHA. 59

no other plant is likely to be mistaken for it. In their
absence it may be told from any of the lichens by the
small, diamond-shaped markings on its upper surface.
A common liverwort growing in damp places {Conoceph-
alus conicus) may be known in its sterile condition by
its larger size, larger areolae and more prominent sto-
mata which in Marchantia are barely visible to the
naked eye, but in Conocephalns are as large as pinholes.
A common greenhouse liverwort of similar appearance
(Lunularia criiciatd) may be distinguished by its cres-
cent-shaped cupules, lacking a border on one side.

Marchantia grows luxuriantly in the greenhouse,
producing an abundance of cupules, and often fruit-
ing. It may be placed on the pots in which other plants
are grown or given a bed to itself.

When gathering material, care should be taken to
save fertile plants with young heads ; in female plants,
especially, some heads should be no larger than a quar-
ter the size of a pinhead, and which at this stage of
growth are to be detected in the sinus at the growing
end of the stem.

To complete the laboratory work requires fresh or
alcoholic specimens bearing cupules and both kinds of
reproductive branches ; fresh specimens of the male and
female heads ; and iodine.

LABORATORY WORK.

GROSS ANATOMY.

A. GENERAL CHARACTERS. Note

1. The flattened horizontal stem or thallus, composing
the larger part of the plant.

6o COMMON LI VER IVOR T.

a. The branches ; all lying in the same plane as the

main axis, except

b. The fruiting branches, consisting of erect stalks,

pedicels, supporting disk-like heads or receptacles
of two sorts, to be found on separate plants :

i. The antheridial (sterile) with scalloped heads,
and

ii. The archegonial (fertile) with star - shaped
heads.

2. The numerous hairs on the under surface of the thallus.

3. The dark brown or purple leaves, somewhat concealed
by the hairs, and closely overlapping to form a low
ridge along the median line beneath.

4. The scales along the sides of the thallus beneath,
some projecting beyond the margin ; more conspicu-
ous on plants grown in damp shady places.

5. Sessile cups or cupules (very prominent when present),
seated on the upper surface of the thallus, containing
bright green flat bodies, the gemmfiB.

B. THE STEM. Note

1. The color of the upper and lower surfaces in fresh
specimens.

2. The well marked median line, midrib ; and the broad
expansions, wings, on either side of it.

3. The indented apex.

4. Mode of branching, dichotomous ; each stem is resolved
into two equally diverging stems, one of which soon
exceeds the other by more rapid growth, giving the
false appearance of being monopodial.

5. On the upper surface the small areas, areola, best
seen on the older parts, in the center of each of which is

MARCHANTIA POLYMORPH A. 61

a. A circular breathing-pore, or stoma, readily de-
tected with the lens.1

6. On the under surface, notice the absence of stomata
and areolae.

■

7. Make an outline sketch of a branching stem to show
the contour, the median line, and the mode of branch-
ing.

8. Mount a transverse section, and if from a growing

ant, notice the pale middle tissue, the green upper

surface, the dark-colored lower surface, and the group
of median leaves projecting downward from the mid-
rib ; if from an alcoholic specimen the color is wanting.
If the specimen is very thin and carefully prepared,
long narrow air-cavities may be seen just beneath the
upper surface with possibly stomata leading out from the
center of some.

C. THE LEAF. Remove the hairs from the lower sur-
face of the stem, and notice

1. The direction and manner of the overlapping of the
leaves.

2. The shape.

3. The curvature and extent of the line of insertion.

4. Illustrate shape, and position on the stem by diagrams.

D. THE TRICHOMES. These are of two kinds, the
hairs and the scales.

1. The //airs. Notice

a. The silky mass extending downward along the

midrib, serving for roots, rhizoids : the part of the
thallus from which they arise.

— ^ _ — „ — j — to_ ... „..

latter being plainly seen without the aid of a lens.

cphalus

6 2 COMMON LIVER WOR T.

b. The closely appressed strengthening hairs on the

wings ; their origin and direction of growth.

2. The scales. Notice

a. The slightly projecting marginal scales, along the

under edge of the thallus ; insertion and direc-
tion.

b. The colorless intermediate scales, midway between

the edge and the midrib ; insertion and direction.

Mount both kinds of scales and notice

c. The shape of each. Draw.

E. THE CUPULE. Note

i. Position on the stem.

2. Shape and size.

3. The degree of smoothness of the outer and inner sur-
faces.

4. The thin margin, infolded when young ; shape and

regularity of the teeth.

5. The gemma within ; remove some and place on a
white surface, and note their form — usually two
notches can be detected opposite each other.

6. Draw a cupule with its gemmae.

F. THE FRUITING BRANCHES.

1. Position on the stem ; note that they are always con-
tinuations of the midrib, and consequently apical,
although sometimes, by the prolongation of the wings,
appearing to rise from the upper surface.

2. The pedicel ; notice

a. Color and striation.

MAKCHANTIA POLYMORPHA. 63

b. The flat, green, posterior1 surface of the arche-

gonial branch, wanting in the antheridial.

e. Pull a pedicel in two and notice the hairs pro-
jecting from a pair of grooves on its anterior

face.

d. Make a transverse section of the antheridial ped-
icel and notice the outline, and the position
and form of the grooves. Draw.

e. In a similar section of the archegonial pedicel

notice the outline, grooves, and the posterior
chlorophyll-bearing portion, with its row of air

cavities. Draw.

3. The head of the antheridial branch, consisting of a

large receptacle and minute and inconspicuous anther-
idia imbedded in it ; notice

a. The general shape of the receptacle.

b. The particular outline of the margin.

c. The broad radiating ridges on the upper and

lower surfaces.

d. The narrow wing-like margin, more easily dis-
tinguished by holding the head toward the light.

e. The numerous scales on the ridges beneath, most

abundant toward the margin.
Cut a vertical section and observe the rather
large oval cavities beneath the ridges ; each cav-
ity contains a single sac, antheridium, holding
the innumerable fertilizing bodies, antherozoids,'
neither distinctly visible. If the antheridium is still

s I. e., the surface looking away from the axis of the stem and corre-
sponding to its upper surface.

3 The antherozoids are far too small to be seen except with a compound
microscope ; they escape through openings in the upper surface, also too
small to be made out in this connection.

6 4 COMMON L I VER IVOR T.

distended with antherozoids, it will completely
fill the cavity and appear as a darker or lighter
spot in the tissues, according to the thickness of
the section, but if the antherozoids have escaped,
the collapsed antheridium remains, although it can
rarely be detected, and the cavity appears empty.
The antherozoids may sometimes be seen in
mass as a faint cloud escaping into the water of
the slide, especially when pressure is applied to
the cover-glass.

g. Make a horizontal section from the upper part of

the head, after first removing a thin surface slice,
and again observe the cavities.

h. Draw an uninjured antheridial branch, giving

prominence to the upper surface of the head.

4. The head of the archegonial branch, consisting of a star-
shaped receptacle and circle of reproductive organs
beneath ; notice

a. The receptacle ; its general shape.

i. The rays, with a longitudinal crease beneath ;
their number.

ii. The cleft, which extends to the posterior side

of the pedicel.

b. The reproductive organs forming groups alternating

with the rays.

c. Carefully separate one of the groups with a needle,

without detaching it, and notice

i. The border, perichsetium, surrounding it, and
inclosing

ii. The several young sporogonia. With a needle

remove the sporogonia to a slide without injur-
ing the perichaetium. Now observe that

iii. The two halves of the perichaetium are united

MARCHANTIA POLYMORPHA. 65

at an acute angle next the pedicel, and by an
infolded flap next the edge of the receptacle.
This flap is best seen by spreading apart the
rays . between which the perichaetium is
situated.

iv. Remove the perichaetium and spread out on

the slide with the sporogonia already placed
there ; notice
a. The fimbriated free edge of the perichcetium.

, The opaque sporogonia with their very short

thick stalks, each inclosed by a delicate
sheath, the perianth, twice the length of
the immature sporogonia, but equaling
or even shorter than the older ones.
Draw.

v. Tear away the perianth and notice that it is

quite free from the sporogonium, which, with
its stalk, can now be seen more clearly. Draw.

d. In a head from a fresh specimen4 having mature

sporogonia protruding from the perichaetia, notice

i. The form of the sporogonia.

ii. The contents ; a fluffy yellow mass when

escaping from a freshly ruptured fruit,
iii. Mount and notice the dust-like part, spores,

and the short delicate hairs, elaters.
iv. Breathe gently upon a mass of dry elaters and

notice the movement caused by the moisture

of the breath.

e. Draw an uninjured archegonial branch, giving

prominence to the under surface of the head.

4 An alcoholic specimen does as well, except to illustrate ii and iv
infra.

6 6 COMMON LI VER WOR T.

MINUTE ANATOMY.

A. THE TRICHOMES. Remove some of the hairs
that are pressed tightly upon the under surface of the
wings of the stem, and under high power notice

i. The shape.

2. The internal projections, sometimes horn-like, branched,

and extending quite across the cavity of the hair.

3. The more or less prominent spiral constriction on which

the projections are seated, giving the walls in optical
section the appearance of alternate scallops.

4. Draw.

5. Compare the loose silky hairs along the middle of the

stem, the true rhizoids, with the preceding. Draw.

Mount marginal and intermediate scales, and notice

6. The cellular structure of each. Draw.

B. THE STEM OR THALLUS. Remove a thin slice
from the upper surface of the stem, mount with the free
surface uppermost, and under high power notice

1. The surface or epidermal cells; their shape and con-

tents.

2. The large breathing pores or stomata, encircled by

rows of special cells, the supplementary guard-cells ;

number of cells in each circle.

3. Draw a stoma with some surrounding tissue.

Remove the cover-glass, remount the section with the
free surface downward, and disregarding other features,
notice

4. The four innermost (now lying uppermost) cells of the

stomata, having more or less prominent projections
(sometimes obsolete) arching over toward the center

of the pore, the true or active guard-cells. Draw.

A1ARCHANTIA POLYMORPHA. 67

Take a very thin slice in the same way from the lower
surface, and notice

5. The shape of the cells of the epidermis, absence of

stomata, and the insertion of the hairs. Draw.

■

Make a vertical section of the stem parallel to the
direction of the radiating tissues of the wings, which is
usually at about an angle of forty-five degrees to the line
of the midrib ; notice

6. The wider colorless under part of the stem.

7. The narrower chlorophyll-bearing upper part.

In the colorless portion of the stem, notice

8. The closely packed parenchyma cells, bordered on

one side by the marginal row of cells forming the

lower epidermis.

9. The shape of the parenchyma cells, their uniformity

of size, and the transverse reticulated thickenings.

10. The smaller size of the epidermal cells, forming an

indefinite marginal row, the walls plain, and either
colorless, purple or brown.

11. Draw several cells of the lower epidermis, and some

of the adjacent parenchyma.

In the upper green layer of the stem, notice

12. The large air cavities, from the bottom of which a

thick growth of (in fresh specimens very green) cells
arises, branching in a cactus-like manner.

13. Note the shape of these cells, their manner of union,

and the rounded (in fresh specimens bright green)

chlorophyll grains. Draw.

In the same section, if sufficiently thin and perfect, ex-
amine

14. The partition wall which separates contiguous cavities,

6 8 COMMON L I VER IVOR T.

and the over-arching roof formed of the single epider-
mal layer of cells. Draw.
When a section is found which has passed through a
stoma, notice

15. The chimney-like structure, the number of cells in

depth, and the shape of the cut ends of the cells, es-
pecially of the outer and innermost ones. Draw.

16. Illustrate the structure of the stem as shown in the

longitudinal section by a diagram.

17. Cut a vertical section of the wing at right angles to the

longitudinal one already examined, and compare with
it : especially note the difference in the outline of the
parenchyma cells, and the frequent absence of reticu-
lated markings. Draw.

C. THE LEAF. Remove a leaf from the stem, best
taken from a young stem where the leaves are comparatively
large and conspicuous, and notice

1. The shape of the cells, absence of markings and of
chlorophyll, and the uniformity of the cells throughout
the leaf. Draw.

Make a transverse section of the stem at right angles to
the midrib, and a good transverse section of the leaves will
usually be obtained : notice

2. The single row of cells forming the blade, or some-
times two or three rows at the base, and the manner in
which the older leaves over-arch the younger. Draw.

D. THE CUPULE. Remove a cupule and place face
upward on the slide, ignoring for the present the gemmae
which float out from it ; press the cover-glass down until the
cupule is sufficiently flattened out, when it will appear as a
wide ring of tissue, the bottom of the cup having been cut
away. Examine with low power

MARCHANTIA POL YMORPHA.

i. The border of triangular teeth ; the fimbriated sides
and elongated apex of each tooth. The inner part of
the cupule is too thick to be seen well.
Place under a higher power.

2. Examine the structure of the. teeth and their marginal hairs
more carefully, and draw. Vary the focus, and notice
whether the inner surface of the cup is smooth or rough.

Remove the cover-glass, turn the specimen over, and ex-
amine as before. Notice that

3. The outer surface of the cup is covered with short hairs

o r papillae .
Make a vertical section passing through the center of a
cupule and through the stem on which it is seated, examine
under low power, and note

4. The two parts of the cupule.

a. The base.

b. The abruptly spreading limb.

c. Arising from the bottom of the cup, flattened tri-

chomes, the gemma, in various stages of develop-
ment.

d. Illustrate with diagram.

Examine the limb under high power, noting

5. The small cells of the inner epidermis, the parenchy-
matous tissue beneath, the absence of a distinctly
marked outer epidermis, and the short one- or two-
celled hairs on the outer surface. Draw.

6. Examine next the base of the cupule, noting the man-
ner in which the layer of air cavities of the stem and
their chlorophyll tissue is continued up the outside of
the cup as far as the insertion of the limb.

7. Upon the inside of the cup, observe

a. The numerous glandular, one-ceiled hairs, and

among them

7 0 COMMON LI VER WOR T.

b. Thicker hairs in various stages of cell-multiplica-
tion, from the first division into two cells by a
transverse wall, to the fully formed many-celled
gemma still attached by its pedicel.

c. Draw part of the bottom of the cup, to show inser-
tion and form of the glandular hairs and young
gemmae.

■

8. Examine under a low power the mature gemma which
have floated from the cupule, and note

a. The shape.

b. The cellular structure.

c. Cells here and there devoid of chlorophyll.

d. The scar left by the pedicel.

e. The pair of vegetative notches placed midway,

one on the right, the other on the left side, in
which, when the gemmae are sufficiently mature, may
be seen

The early stage of the new plantlets in form of
delicate papillae.

g. Draw.

E. THE ANTHERIDIAL BRANCH.

i. The pedicel. Pull in two a pedicel and remove some of
the hairs which protrude from two grooves on its pos-
terior face, and lay upon a slide. Now make a trans-
verse section of the pedicel and mount with the hairs.

Under low power, notice

a. The general outline of the section, the two con-
spicuous grooves or channels, and the uniformity of
the whole tissue. Illustrate with diagram.

Under high power, notice

b. The colorless dense parenchyma forming the mass

of the pedicel, bounded by the surface row of small

MARCHANTIA POLYMORPHA. 71

epidermal cells, in fresh specimens usually colored
purple or brown. Draw.

c. The overlapping projections inclosing the right

and left channels or grooves, from the apex and
sides of which arise leaves, which seen in cross-
section appear as a single row of cells, or double
rowed at the base ; observe the manner of infold-
ing, comparing sections when convenient from
different parts of the same pedicel, and from
different pedicels, drawing the most interesting.

d. In some of the grooves will be found excellent

cross-sections of the hairs. Examine now the hairs
pulled from the grooves. Draw.

e. Remove a thin paring from the anterior surface of

the pedicel, examine the epidermal cells, and, by
varying the focus, the face of the leaves. Draw

a few cells of each.
2. The receptacle. Take a slice from the ridges on the

upper surface of the receptacle, mount with the free
surface uppermost, and notice

a. The stomata and epidermal cells.

b. The pores, around which the epidermal cells con-
verge, the mouths to the underlying cavities con-
taining the antheridia.

c. Draw.

Remount the section with the free surface downward,
focus on the cut surface, and in the thicker part of the
section notice

d. The large air cavities, producing from the sides

branched chlorophyll filaments like those of the
stem. Focus deeper into the cavities and notice

e. The stomata, the four innermost cells inflated and

almost or quite closing the pore of the stoma.
The pores of the antheridial cavities situated in

7 2 COMMON LI VER WOR T.

the walls between the air cavities; also the disposi-
tion of the surrounding tissue.

Cut a rather thick vertical section a little to one side

■

of the center of an immature receptacle, and notice

g. The chlorophyll cavities,with their chlorophyll cells.

//. The much larger antheridial cavities, which are

quite likely to be empty, or may contain the
membranous remains of the antheridial sac, or may
be more or less filled with

3. The antheridium with its paraphyses ; notice

a. The shape of the antheridium.

b. The pedicel by which it is attached to the bot-
tom of the cavity.

c. The structure of the wall, brought into view by

focusing on the part nearest the eye.

d. The wall as seen in optical section, only a single

cell in thickness.

e. The uniform contents, consisting of very small

squarish cells, filled with colorless protoplasm.
The several unicellular paraphyses surrounding
the base of the antheridium, and not much longer
than its pedicel ; best seen when the antheridia are
young.

g. That the antheridia are younger toward the margin

of the head, and older toward the center.
h. Draw an antheridium with its paraphyses.

4. The anther ozoi ds ; if the section just examined be from
a freshly gathered specimen, the contents of many of
the antheridial cells will have escaped into the water of
the slide6 : notice

5 An excellent way to obtain antherozoids for examination is to place
a small drop of water on a slide and hold a freshly gathered head in it for
a few moments, when, if the antherozoids are ripe and abundant, they
will make the water milky.

MARCHANTIA POLYMORPHA. 73

a. The rapid motion of the antherozoids, becoming

slower and slower until after some time they come
quite to rest.

b. Their form ; a slender filament, at the anterior end

of which may be detected,when the motion becomes
sufficiently slow,

c. Two very delicate vibratile cilia; the form and

motion may be more readily studied by staining
with iodine, and watching the antherozoids as they
pass gradually under its influence.

d. The delicate hyaline vesicle and its contents,

dragged about by some of the antherozoids

until finally detached.
If the section be from an alcoholic specimen, some an-
therozoids will have escaped, or can be made to escape by
pressing on the cover-glass, when the form can be studied
as before, but the filaments will be found quite closely
coiled, the cilia difficult to detect, and the vesicle probably
invisible.

F. THE ARCHEGONIAL BRANCH.

1. The pedicel ; in a transverse section under low
power, notice

a. The general outline.

b. The two grooves.

c. The posterior plate containing air cavities and

chlorophyll tissue.

d. Illustrate with diagram.
Under high power, notice

e. The larger rounded anterior part, in every essential

like that of the antheridial pedicel.
The smaller flattened posterior part in which lie
i. The air cavities, like those of the thallus, ex-
cept smaller, sparsely provided with

7 4 COMMON LI VER WOR T.

ii. Chlorophyll-bearing filaments , springing indif-
ferently from the floor or walls,
iii. The (usually single) layer of small cells form-
ing the floor, partition walls, and roof of the
cavities,
iv. The stomata, these will occasionally be cut
across ; note the number of cells in depth,
and their relative size.
• v. Make a drawing to illustrate the several

points.
Make a longitudinal antero-posterior section and note
g. The length of the parenchyma cells, and shape of

the air cavities.
h. Remove a thin paring from the flat posterior

surface of the pedicel, and mount with the free
surface uppermost, noticing the epidermal cells and
stomata. Draw.
*. Remount the section with the free surface down-
ward ; note the relative size of the air cavities,
and the appearance of the stomata.
Cut off a pedicel near the base, make an antero-posterior
longitudinal section of the basal portion, together with the
stem from which it arises, and note

j. The continuity of the tissues of the pedicel with

those of the stem.
Cut off a pedicel near the head, make an antero-posterior
longitudinal section passing through the pedicel and through
the cleft in the receptacle, and note

k. The continuity of the tissues of the pedicel with

those of the receptacle.
2. The receptacle ; cut a transverse section of one of
the rays, and notice

a. The central cavity in which lie numerous hairs

like those in the grooves of the pedicel.

MARCHANTIA POLYMORPHA. 75

b. The encircling tissues, indented at one point, yet

continuous ; notice further

i. The internal portion of uniform parenchyma,
ii. The. external row of air cavities, containing

chlorophyll-bearing filaments, and provided
with stomata, essentially like those of the
pedicel,
iii. Papillary trichomes arising from many of the

epidermal cells.
Using an immature branch, cut a transverse section
across two or three rays nearer the center of the head and
passing through the groups of sporogonia, notice

c. The central cavity, much smaller than in the rays.

d. The right and left sides, which instead of being

united, are prolonged into the perichcetiumy so
that the perichaetial leaf on the right side of the
group of sporogonia belongs to the left side of
the right hand ray, while the perichaetial leaf on
the left side belongs to the right side of the left
hand ray.

e. The section of the perichaetial leaves, one cell in

thickness, or sometimes two at the base.
Examine the flat surface of the perichaetium, the
shape of the cells, and the notched and fimbriated
margin. Draw.

g. The bent filaments, paraphyses , composed either

of a single row of cells, or of two or more
united rows for part or the whole length.
Draw.

3. The archegonia,8 the flask-shaped bodies among the

paraphyses, consisting of

6 Bear in mind that the archegonia are called sporogonia after fertiliza-
tion and a certain amount of growth has taken place.

COMMON LIVER WOR T.

a. The bulbous base : in optical section make out a

single layer of cells inclosing a central cavity.

b. The long neck?

c. A ring rising up around the base in some cases,

the early stage of the perianth.

d. Draw.

4. The sporogonia ; selecting the immature ones, notice
under a low power

a. The peria?ith j its deeply notched margin, which

is usually twisted over the fruit ; observe the
cellular structure. Draw.

b. Tear away the perianth, examine the surface of

the sporogonium and its stalk, and notice the
remains of the neck of the archegonium.

c. Crush some of the sporogonia by pressing upon

the cover-glass, noticing the escaping contents
consisting of slender threads having granular
protoplasm and pointed ends, the immature elaters,
and rows of young spores, both radiating from the
base of the fruit. Draw.

d. Examine some mature spores ; notice

i. The wall.

ii. The contents.

e. Examine the mature elaters ; notice

i. The delicate wall, not easily distinguished.

ii. The spiral bands.6

iii. Examine some dry elaters without a cover-
glass, and observe the movements when damp-
ened by the breath.

7 These archegonia, unless taken from a very young head, are mostly
sterile, not having been fertilized, as shown by the shriveled neck, and
the absence of a well defined protoplasmic mass in the basal cavity.

8 Their number can be ascertained by the method used for Spirogyra,
p. 36.

MARCHANTIA POLYMORPHA. 77

5. Section or crush a young archegonial head not exceed-
ing a pinhead in size, and giving attention only to the
archegonia, notice

a. The single layer of cells forming the wall of the

bulbous part, passing into

b. The few rows of cells forming the neck, appearing

in optical section like two rows, ending above in

c. The stigmatic cells, which are spread apart at the

time of fertilization.

• d. The well denned cavity in the bulbous part, con-
taining (if not yet fertilized)

e. The globular oosphere.

The narrow canal extending the length of the
neck, through which the antherozoids reach the
oosphere to fertilize it.

ANNOTATIONS.

In a morphological point of view Marchantia is a
plant of unusual interest, on account of its remarkable
degree of differentiation. Taking first the vegetative
portion, we have in the thallus a structure that is
typically shown in lichens and other plants belonging
to the thallophytes. More strictly speaking the Mar-

chantia stem is onlv thalloid, for there are the rud

ments of leaves on its underside, while a true thallus
has no leaves. The prostrate position of the stem has
necessitated the specialization of the upper surface for
the purposes of assimilation and respiration, and the
lower surface for the absorption of moisture and the
other nourishment which comes with it.

The chlorophyll bodies, like those of all higher plants,

COMMON LI VER WOR T.

consist of rounded grains of protoplasm in which the
chlorophyll proper is contained, the protoplasmic body
being readily seen after the pigment has been extracted
by alcohol. Such grains are scattered throughout the
thallus, but are only effectively developed in special
cells, which arise from the floor of cavities formed by
depressions in the surface of the thallus, and which are
overarched by the epidermis at a very early stage of
growth.9 Communication with the outside air is
secured by means of peculiar and highly developed
stomata.10 They are wider in the middle than at the
upper and lower openings, each stoma forming a small
air-chamber. The border to the outer opening is sharp
edged and immobile, while the inner one is formed of
inflated cells which act as regulators to the passage of
air and moisture. Altogether a very perfect arrange-
ment is thus made for the aeration of the chlorophyll
tissue without undue loss of moisture.

The under surface of the stem is provided with copi-
ous hairs, those of the wingsdeveloped to give support,"
toward which the internal thickenings and spiral con-
striction of the walls contribute, while those of the mid-
rib, larger, smooth-walled, and somewhat colored, serve
to fix the plant to the earth and to take up from it the
water and nutriment required, i. e. to perform the
office of roots. In a physiological point of view

9Leitgeb,Die Athemoffnungen der Marchantiaceen, in Sitzber. d. k. k.
Akad. in Wien, lxxxi, 1880. This differs from the older view which
ascribed the openings to a separation of the epidermis from the under-
lying tissues. Sachs, Text-book 1st and 2nd Eng. eds.

10 Described and illustrated by Voigt, Beitrag zur vergleichenden
Anatomie der Marchantiaceen in Bot. Zeit., 1879, P- 729-

11 According to Strasburger. Das botanische Practicum, p. 314.

MARCHANTIA POLYMORPHA. 79

the root-hairs are not merely rhizoids but real roots,
and such they have been called by Sachs recently, who
no longer holds to the morphological distinctions of
root, stem, leaf and hairs, but refers all vegetative
organs of higher plants to two categories, viz : the root
and the shoot}'*

The scales are organs that we shall meet with in a
more developed form when we reach the ferns. They
differ from the leaves in size and position, but more
especially in having the cells empty and lifeless.

The internal structure of the stem is interesting on
account of the thickenings of the cell-walls for secur-
ing extra strength, and the absence of any differentia-
tion of the tissues along the midrib except the moder-
ate change in the shape of the cells.

The branching of the stem is a fine example of true
dichotomy where the growing point is symmetrically
halved, and each half gives rise to a branch. M In this
case one branch develops faster than the other, and
the appearance is soon the same as if it had arisen as a
lateral branch (see fig. 2). The tissues of the wings
reach their growth more rapidly than those of the
midrib, and so the growing end is constantly indented.

The leaves have little of the appearance we associate
with the term, as commonly used. They are, indeed,
very depauperate leaves, and serve simply as organs
of strength, through the power of the protoplasmic
contents of the cells to maintain turgidity.

The asexual propagation in Marchantia is of two

"Vorlesungen ttber Pflanzenphysiclogie. p. 5.
^Sachs, Text-book, 2nd Eng. ed., pp. 177, 181

8 o COMMON LI VER WOR T.

kinds. One is a very common method, by which the
stems die off at the older end as fast as they grow at
the other. In this way the branches are eventually
separated from each other and become independent
plants. The other is a peculiar method by which cer-
tain hairs at the bottom of cupules grow into flat green
plates, the gemmae, which as they become mature are
pushed out of the cupules by the aid of the secretion
from the glandular hairs. " The gemmae have their
direction of growth changed at a very early stage by
the formation of a right and left growing point, so that
the young plantlet is bifurcated at its outset. • When
a gemma has fallen upon the ground, the side which
happens to be uppermost is developed as the upper
surface of the thallus, and the other becomes the lower
surface. " The root-hairs grow from the cells devoid
of chlorophyll.

The sexual reproduction is among the most highly
developed of that shown by the liverworts. The organs
are upon branches whose modification is so interesting
that it will be necessary to examine it somewhat care-
fully. The plants are dioecious, bearing the reproductive
organs on separate individuals. In each case the repro-
ductive branch consists essentially of an attenuated por-
tion,the pedicel, terminated by an expanded portion, the
head, on which last the sexual organs are borne. The
pedicel is not a single branch, but two which are the
result of dichotomy at the point where it leaves the

14 Fide Strasburger, Das botanische Practicum, p. 436.

15 Engelmann, Ueber die Einwirkung des Lichtes auf den March-
antienthallus in Arb. d. bot. Inst, in Wurzburg, Bd, ii, p. 665 ; Mirbel.
Mem. Acad. Sci.de Fr., xiii (1835), p. 355.

MARCUANTIA POLYMORPHA. 81

thallus. These two do not separate, and, indeed, were it
not for the two double rows of leaves along the anterior
(under) surface* which give rise to the two grooves with
their strengthening hairs, it would be difficult to show
that any branching had occurred.

The pedicel of the female head is made up of exten-
sions of the tissues of the thallus, but without the
development of the wings. The head is formed by
sudden branching, and as dichotomous branching must
always be in pairs, it results in an even number of
branches which are spread out like a very widely open
fan. But counting the rays of the head always gives
an odd number, which is explained by the fact that the
growing point is not at the tip of the rays but at the
sinus between them, while the rays are formed, as in
the thallus, by the extension of tissue on either side
the growing point. Thus each ray, with the exception
of the ones nearest the cleft of the head, stands between
two growing points, while those next the cleft have a
growing point only on one side of them. The hairs of
the rays correspond with the hairs of the wings, and
extend into the grooves of the pedicel.

If now we turn to the male branch, we shall
find the pedicel only differs from that of the female in
possessing no chlorophyll tissue on its posterior (upper)
surface. The tissues of the upper surface of the head
were at an early period of growth continuous with those
of the thallus, but, owing to some unknown cause, they

have not continued to expand along with those of the
ventral side in forming the pedicel. The head is made
up of branches, as in the female head, and like that is
not a radial structure, but zygomorphic. The cleft is

8 2 COMMON LI VER WOR T.

not so evident as in the other case, and the number of
rays is even and not odd, the latter being the result of
the growing point being at the ends of the rays, instead
of at the sinuses. The various correlated changes can
readily be worked out by the student.

It now remains to account for the position of the
two kinds of organs, one being on the upper surface
and the other on the lower. We must know in the
first place that the antheridia are modified hairs, which
originally started on the surface, but became inclosed
in cavities by the surrounding tissues growing up about
them. They evidently belong to the upper surface
from their position, and the fact that those nearest the
growing edge are the youngest. In the female inflor-
escence we find that the organs nearest the edge are
not the youngest, but the oldest. We can only explain
this by supposing that they belong to the upper sur-
face, but are brought below by the turning under of
the growing point.16 The perichsetium is the thin ex-
panded edge of the thallus.

The antheridia and archegonia originate, as in the
case of the gemmae, from papilliform hairs, which divide
into two cells by a transverse wall, the lower cell becom-
ing the pedicel, and the upper the body of the organ.17
Paraphyses, which are always sterile bodies, are very
common among the cryptogams; their significance is
not understood.

The antherozoids may be taken as the type of the
motile male element in fertilization. They are formed

Strasburger, Das botanische Practicum, p. 439 ; Leitgeb, Unter-

suchungen iiber die Lebermoose, vi, 1881.
17 Sachs, Text-book, 2nd Eng. ed., p. 348.

MARCHANTIA POL YMORPHA. 8?

of free protoplasm, having no cellulose covering. The
hyaline vesicle which is sometimes seen attached to
them arises from the internal part of the protoplasm
of the cell, the outer portion of which produces the
cilia, and the nucleus at the center of the cell the body
of the antherozoid.18

The archegonia separate a mass of protoplasm in
their interior, the oosphere, which is essentially a naked
cell. After fertilization it divides in a perfectly regular
manner to form the sporogonium. The fertilization is
prepared for by the conversion of the axial row of cells
of the neck into mucilacre, the swelling of which forces

the stigmatic cells apart, and a passage-way is formed

to the naked oosphere. The antherozoids pass through
this channel, become buried in the oosphere, and the
fertilization is complete.

The elaters by their strongly hygroscopic character
assist materially in forcing out and distributing the
spores.19

18 Strasburger, Das botanische Practicum, p. 455.

19 The student should consult Ilofmeister's Higher Cryptogamia, which
contains a very full statement of the development of Marchantia, with
historical references up to 1862.

MOSS.

A trie hunt undulatum Beau v.

PRELIMINARY.

MOSSES appear so much alike to those who have not
given special attention to them, that it is more difficult
to definitely point out a particular species than in the
other plants of the book. The one selected for study
is widely distributed, and very common, forming carpet-
like patches in woods, and on shady banks. The single
plants stand from two and a half to four centimeters
(one to one and a half inches) high. The leaves, which
are abundant, are five millimeters (quarter of an inch)
or more long, narrow, with wavy sides ; the undu-
lations appear, when the leaf is held to the light, as lines
passing obliquely from the middle to the margin.

The male and female plants are usually found in sep-
arate patches, as in Marchantia. The male flowers (see
fig. 5) are easily recognized by being cup shape, and are
distinguished from the rosette of leaves terminating a
rapidly growing stem by having a distinct, rather flat
bottom to the cup. They are readily found at almost
any time during the year, and are especially abundant
in early summer.

The female flowers, which are less common than the
male, differ so little in external appearance from the
ordinary vegetative condition, that it often requires a

A TRICH UM UND ULA TC/Af. 85

protracted search to find them. A patch of female
plants may usually be detected by the presence of the
fruit in some condition of growth or decay ; if, on cut-
ting vertically through astern taken from such a group
of plants, the terminal leaves of which are well folded
over the end, making a loose bud, the stem appears to
terminate abruptly within the bud, it may be inferred
that the female flowers are found. It is, however,
necessary to use the microscope to render it sure.
They are to be sought for especially in May. If the fe-
male flowers can not be found, those of other mosses will
answer the purpose. Polytrichum is one of the largest
of our mosses, and has female flowers much like Atri-
chum, while Milium, Funaria, and others have them
somewhat larger, more conspicuous, and nearly as com-
mon as the male.

The fruit is a nearly straight cylindrical pod with a
conspicuous pointed beak, borne erect on a stalk about
two or three centimeters (an inch) long (see fig. 4). Col-
lect both green fruit from which the hood (calyptra) has
not fallen, and that which is thoroughly ripe with the
hood and lid both gone, exposing the teeth.

The protonema is not so abundantly produced as in
many mosses. Keeping vigorous growing plants in an
inverted position in a moist atmosphere for some time
by turning a bell-glass over them, will sometimes be
sufficient to develop it. The protonema from other
mosses (Mniutn, Barbula, etc.) is, however, usually
found with ease, or may be produced as above, and will
serve for the study.

The materials required for the present study are

MOSS.

alcoholic specimens showing male and female flowers,
and fruit ; fresh specimens showing protonema and male
flowers ; potassic hydrate ; and iodine.

LABORATORY WORK.

GROSS ANATOMY.

A. GENERAL CHARACTERS. Note

i. The vertical stem ; unbranched, or branching only from
the base.

2. The leaves clothing the stem.

3. The root-hairs, rhizoids j often forming a close felt at
the base of the stem.

4. At the summit of some of the stems, the flowering heads
of two sorts :

a. The male heads forming a terminal rosette of green

leaves.
I?. The female heads with the terminal leaves folded

over each other forming a small bud.

5. At the summit of other stems the fruit or sporogonium,
consisting of

a. The slender stalk or seta.

b. The cylindrical pod or capsule.

c. The hood which fits closely over the end of the

pod, and may be easily pulled off, or has dropped

off of itself, the calyptra.

6. Among thrifty plants that have been kept under a
moist bell jar for several days, notice the green threads
growing out over the soil, the protonema.

B. THE RHIZOIDS. Remove some from the stem.

mount, and notice the small tangled hairs forming the mass.

A TR I CHUM UNDULATUM. 87

C. THE STEM. Notice *

1. The size and shape.

Remove the leaves near the base, mount a transverse sec-
tion, and notice

2. The outline of the section.

3. The three tissue regions ; the peripheral brown tissue,
the axial tissue forming a light spot in the center, and
the intermediate colorless tissue.

1). THE LEAVES. Notice

1. The manner of arrangement on the stem.

2. The difference in size on different parts of the stem.

3. The shape of

a. The lowest, scale leaves.

b. The middle, foliage leaves.

c. The uppermost on flowering stems, forming the

outer portion of the head, perichaetial leaves.

4. The structure ; a thin lamina, with a thicker median
line, the midrib.

5. The character of the margin, especially toward the
apex.

6. In the foliage leaves, the undulations passing obliquely
outward from the midrib to the margin ; their absence
in the other sorts.

7. Draw a leaf of each sort — scale, foliage and perichaetial.
E. THE FLOWERING HEAD.1

1. The male heads. Notice

Sachs

has

parts of a flower are seated. The analogy of the several parts of the
moss " flower" to those of the head of a composite (e. g. sunflower) has
determined the use of corresponding: terms.

MOSS.

a. The shape.

b. The central disk.

c. The leafy continuation of the stem arising from the

center of some of the heads.

Cut a head in two vertically, and note

d. The enlarged end of the stem, receptacle, on which

the disk is seated.

e. Draw the half head, looking at the cut surface.

Remove the disk with the point of a scalpel, separate the
parts on a slide, mount, and notice

The broad chaff, resembling the scale leaves ; the
shape, especially the narrowed base. Draw.

g. Numerous narrow bodies of nearly the same

length as the chaff, antheridia, the male reproduc-
tive bodies.

h. Slender filaments of same length as the anther-
id ia, paraphyses.

2. The female heads. Make a vertical cut exactly
through the center, and notice

a. The absence of any thickening of the stem to

form an enlarged receptacle.

b. The absence of a disk.

Remove the central portion, separate well on a slide,
mount, and notice

c. The numerous filaments, the paraphyses.

d. A few bodies, not exceeding a half dozen,2 about

as large as the antheridia, but swollen somewhat
near the base with the upper portion slender, the
archegonia, the female reproductive bodies.

F. THE FRUIT. Notice

2 The fewness of the archegonia, and the difficulty of securing them
at just the right stage of growth, often makes an extended search neces-
sary in order to demonstrate them.

ATRICHUM UNDULATUM. 89

i. The stalk or seta.

a. The length.

b. Character of the surface.

c. The slightly expanded end from which the cap-

sule arises, apophysis.

Take a specimen that has been boiled a minute or two in
potassic hydrate, and pull the seta from the leafy portion,
taking care that it does not break off, but comes away

smooth, and notice

d. The pointed base.

2. The pod carried by the seta, the capsule, with its calyp-

tra ; notice

a. The manner in which the calyptra fits upon the

apex of the capsule.

b. Shape of the calyptra.

c. Pull away a calyptra and note its texture, and the

roughness of its apex. Draw.

d. The shape of the capsule, and nature of the sur-
face.

e. The hemispherical apex bearing a long beak,

together forming a removable lid, the operculum.
The obliquity and slightly eccentric position of the
beak.

g. Draw a capsule.

//. Pull off the operculum from a mature fruit, and

notice the rim of the capsule on which the edge
of it rested.

i. Rising from the rim, a large number of deli-

cate, incurved teeth, together forming the peri-
stome.

/. Count the teeth ; the number will be some multiple

of four.
k. The delicate epiphragm stretched between the

apices of the teeth ; to be better displayed shortly.

MOSS.

/. Draw the upper part of the capsule showing the

teeth and epiphragm.

Divide the capsule longitudinally, and notice
m. The axial column running through the center, the

columella, the expanded apex giving rise to the
epiphragm.

n. The cavity between the columella and wall of the

capsule, either empty or filled with a powder, the

spores.

o. Make a diagram of the section.

MINUTE ANATOMY.

A. THE RHIZOIDS. Under high power, notice

i. The straightness, uniformity of diameter, and mode
of branching.

2. The character of the lateral walls, and the position and
direction of the cross-partitions, if any.

3. Draw.

4. Notice the manner in which some of the rhizoids are

coiled around each other, forming ropes.

B. THE PROTONEMA. Notice

1. The arrangement of the cells.

2. The thinness of the walls, and position of the cross-

partitions.

3. The contents.

4. Draw.

C. THE STEM. In a transverse section taken from the
lower scaly part of the stem, notice

1. The three regions.

a. The peripheral, with the cell walls reddened.

ATRICHUM UNDULATUM. 91

b. The axial, with the cell walls colorless.

c. The intermediate, with cell walls yellowish.

2. The peripheral tissue. Note

a. The outer layer, epidermis, occasionally bearing

root-hairs.

b. The similar underlying cells, merging into

3. The intermediate region. Note

a. The larger cells with the walls becoming thinner

toward the center of the stem.

b. One or more leaf traces, composed of

i. A crescent shaped layer of small round cells

with very thick walls, the dorsal cells.

ii. Lying in the crescent, about two rows of

larger cells with rather thin walls, the conduct-
ing cells, inclosing

iii. Two or three small cells, appearing much

like intercellular spaces, the central cells.

iv. Still further toward the center of the stem, a

few scattered cells similar to the dorsal, the

basal cells.

c. Note that the leaf traces nearest the center of the

stem are the simplest. Sometimes one may be found
at the very center of the stem.

4. Draw one of the largest leaf traces with some of the

surrounding tissue including the adjacent epidermis.

5. The axial region. Note

a. The more or less strongly thickened walls of the

cells.

b. The small groups of cells with the intervening walls

very thin and membranous.

c. Draw a portion of the axial region.

6. In a longitudinal section of the stem, identify as many
of the different sorts of cells as possible, noticing

MO SS.

a. The shape of the cells. Draw.

b. The direction taken by the leaf traces.

Remove the scales from a stem, cut a slice from the
surface, and notice

7. The shape of the epidermal cells. Draw.

D. THE LEAF. Make a transverse section just below the
middle of one of the largest foliage leaves, and notice

1. The larger central portion, the midrib.

2. The plate of cells, usually a single row, extending right

and left from the midrib, the lamina.

3. The midrib. Note.

a. The epidermis : a single layer of cells on the con-
vex (under) side ; a layer on the flat (upper) side,
each cell of which gives rise to a vertical
two to four or more cells in height. If from a
fresh specimen, note the contents of the cells.

b. The leaf bundle; compare the several parts, the

dorsal, basal, central and conducting cells, with the
corresponding parts of the leaf trace which enters
the stem, already examined.

c. Occasionally a few cells between the dorsal and

basal cells and the adjacent epidermis, resembling
the latter.

d. Draw the midrib.

4. The lamina. Note

a. The shape and contents of the cells.

b. The smaller grouped cells at the margin of the

lamina.

c. Draw.

Mount a foliage leaf entire with the upper side upper-
most, and beside it another with the lower side, uppermost ;
using low power, notice

ATRICHUM UNDVLATUM. 93

d. The cells of the main part of the lamina with their

contents.

e. The marginal cells, produced into

The sharp forward-pointing teeth, which are often
in pairs : observe the distribution of the teeth
along the margin, also similar teeth on the under
side of the leaf along the summits of the undula-
tions and on a part of the midrib.

g. The surface of the midrib : observe the shape of

the cells on the under side ; the rows of chlorophyll
tissue on the upper side, which begin near the base
of the leaf and extend nearly to the apex, seen as
plates in the transverse section.

Under high power, notice

//. The elongated marginal cells, and the shorter cells

forming the teeth.
i. Draw a portion from near the middle of the leaf,

showing teeth, marginal cells and some adjacent

laminal cells.

E. THE FLOWERING HEAD. Remove the disk from
a male head, and mount, well separated ; notice

i. Numerous hairs, the pa raphyses.

a. The walls, cross partitions, and contents.

b. Draw.

2. The antheridium.

a. The shape.

b. The elongated cells of the body.

c. The short cells of the pedicel.

d. The large apical cell, in antheridia which have not

yet burst.

e. D raw.

3. The antherozoids. If from a fresh specimen, notice

MOSS.

a. The movement. Apply iodine, and watch them as

they gradually come under its influence.

b. The for?n ; a slender body, with a pair of cilia at

the anterior end.

c. The colorless vesicle sometimes to be seen attached

to the posterior part.

d. Draw.

Crush an immature antheridium by pressing on the cover-
glass, and as the contents escape, notice

e. The antherozoids coiled within the mother-cell.

If alcoholic specimens are used, the antherozoids may be
seen within the mother-cell, but the parts can not be made
out.

Tear apart a female head, mount, and notice

4. The paraphyses ; shape and structure.

5. The archegonia.

a. The enlarged ventral portion.

b. The long neck.

c. The short thick pedicel.

d. Focus upon the surface, and draw some cells of
each portion.

Treat with potassic hydrate to render the archegonia
more transparent, focus so as to give an optical section, and
notice

e. The two rows of cells forming the neck, the ter-
minal cells of which are
The stigmatic cells.

g. The canal along the axis of the neck.

//. The two or more rows of cells surrounding the

ventral portion .
i. The small mass of protoplasm lying deep in the

center of the ventral portion, the oosphere (if not
yet fertilized).

ATM CHUM UNDULATUM. 95

j. Draw.

F. THE FRUIT.

i. The seta. In a transverse section near the base,

notice

a. The outer portion of thick walled, deeply colored

tissue, passing abruptly into

b. Loose, thin walled, colorless tissue. Within these

and almost completely separated from them

c. A core composed of the following tissues :

i. An outer row of large, round, thin walled cells,
ii. Adjoining this a layer of smaller angular cells

with walls somewhat thickened, and
iii. In the center, a few small cells with thin

colorless walls.

d. Draw a sector of the section.

e. Notice the shape of the epidermal cells in a sur-
face slice. Draw.

Examine several longitudinal sections, and deter-
mine as many of the tissues as possible. Draw.

2. The capsule. Make a transverse section through the
middle of an immature capsule. Under low power,
notice

a. Two parts, separated by a cavity :

i. The outer, the wall of the capsule.
ii. The inner, the axial cylinder.
iii. Uniting these, if not torn away in making

the section, delicate radial filaments.

b. The parts of the axial cylinder.

i. The narrow outer part, the wall of the spore
case.

ii. The large central part, the columella.
iii. A dark line separating the two, the mother-
cells containing the young spores.

MOSS.

c. Make a diagram of the section.
Under high power, examine in succession

d. Each of the tissues enumerated.

e. Draw a sector of the section.
Make a transverse section of a mature capsule, notice

The thick walled, deep colored and strongly cuti-
cularized epidermis.
g. The colored cells of the spore sac.
Make a longitudinal section of a nearly mature capsule
(after removing the calyptra), and with low power, notice
at the base of the capsule

h. A mass of large thin walled cells forming the

apophysis .

/. Above the apophysis several layers of smaller,

more regular cells, from which arise the various

parts of the axial cylinder.
j. At the upper end of the capsule, notice

i. The large central mass of wide thin walled

cells, resting upon the axial cylinder and
inclosed by the operculum. .

ii. The line of separation between this and the
roof of the operculum, showing, more or less
clearly, the delicate membrane which is ex-
posed by the detachment of the operculum,
the epiphragm.

iii. The small deeply colored cells of the rim of

the capsule.

iv. The curved lines extending from the rim
to the edge of the epiphragm, the structure
usually not well shown, the teeth of the peri-
stome.

v. The tissue of the operculum on the sides
where "it shuts over the teeth, of the roof
adjoining the epiphragm, and of the beak.

A TRICHUM UND ULA TUM. 9 7

k. Illustrate the arrangement of the tissues as seen

in longitudinal section by a diagram.

Take a nearly mature capsule, remove the thinnest pos-
sible slice from the side of the operculum with the razor
inclined toward the beak ; the next slice will include a por-
tion of the peristome, in which notice

/. The rows of cells from which the teeth are

formed, and their manner of thickening. Draw.

Make several transverse sections through the rim and
operculum, and study

///. The formation of the teeth from groups of cells.

Take a mature capsule, mount a number of entire teeth,
and notice

. n. The shape and structure of the teeth. Draw.
o. Flatten out a calyptra, and observe the cellular

structure, especially at the apex. Draw some
of the cells.

3. The mature spores ; note under high power

a. The shape.

b. The wall and contents.

ANNOTATIONS.

The step from Marchantia to Atrichum is not so
great as that which intervenes between the several
preceding examples, and yet the advancement is well
marked and especially significant. With the upright
growth of Atrichum is correlated the disposition of the
leaves and root-hairs. The leaves being green, relieves
the stem of its assimilative duties, and in consequence
the smaller size and greater firmness better meet the
requirements. The root-hairs simulate true roots even

MOSS.

more closely than those of Marchantia. A curious
habit of the root-hairs of this and the allied genera is
the manner in which they coil about each other, form-
ing branching ropes, and adding to their effectiveness
as hold-fasts.

The stem of Atrichum shows considerable diversity
of tissues. The axial groups of cells with thin inter-
mediate walls are peculiar to a few of the higher
mosses. A noticeable feature is the absence of a well
marked epidermis, which is doubtless to be associated
with the fact that the cells beneath have thick walls, that
there are no chlorophyll tissues to be aerated, and that
the numerous leaves assist materially in giving protec-
tion. The absence of stomata is also to be accounted
for by the absence of chlorophyll tissues.

The leaves show a distinct midrib and blade, and
possess all the essential features of true foliage leaves.
The blade being only one cell thick is apparently the
same on both sides, and possesses chlorophyll bodies

■

which are typical for all higher plants. A selvage of
strong cells runs around the edge of the lamina to
guard against tearing, while numerous teeth act, to
some extent, as a protection. To give additional aerat-
ing surface, there are a number of plates, like narrow
auxiliary blades, placed along the upper surface of the
midrib. They are still better developed in Polytri-
chtim, but are entirely wanting in most mosses. As
there is no epidermis or other protective structure to
guard against excessive evaporation, an ingenious sub-
stitute is afforded by the inrolling of the sides of the
leaf whenever the turgidity of the cells is disturbed.

But no feature in the histology of mosses is more

A TRICHUM UND ULA TC M. 99

significant and interesting than the leaf bundle of the
midrib. It is the simplest form of a structure that
plays a most important part in higher plants — the
framework of wood and bark which enables them to rise
above the surface of the earth and display their tissues
to the wind and sun under conditions most favor-
able for growth. The bundles of Atrichum which are
as highly developed as in any of the mosses, resemble
those of higher plants more in their position and
function than in structure.* Their place in the leaf
and their manner of forming leaf-traces in the stem are
like those of higher plants. The cells for strength are
the dorsal and ventral, being the same except in posi-
tion, and the cells inclosed by these transport the sap.

Passing to the sexual reproduction, we notice that
the organs concerned are much like those of Marchantia.
The differences requiring consideration lie in the modes
of displaying and protecting the organs. Instead of
sinking the male organs in a flattened receptacle, they
are placed in the axils of protecting leaves diverted to
that use, and instead of bringing the female organs
under the protecting roof of the receptacle they are
sheltered from rain and other excessive moisture by
the overlapping of the perichaetial leaves.

An item of historical interest in this connection is
that it was in the mosses that the sexual organs of
cryptogams were first demonstrated by Hedwig4 in
1783, but it was not till the publication of Suminski's
researches on the ferns,5 as late as 1848, that their

3 A very full illustrated account of the histology of the stem and leaves
of mosses is given in Pringsheim's Jahrb. f. wis. Bot., vi.

4 Theoria Generationis, p. 138.

5 Zur Entw. der Farrnkrauter.

100

MOSS.

sexual character was fully established. It was also in
mosses and liverworts that the antherozoids were first
detected, being seen by Schmidel6 in 1762, but without
detecting their cilia, which were discovered by Unger7
in 1837.

After fertilization has occurred the oosphere clothes
itself with a cell wall, and grows at once into a fruit, as
in Marchantia. This fruit is in many ways remarkable,
as will be more apparent in some respects after study-
ing the ferns and club-mosses. It will be remembered
that in the plants already studied, with the exception
of Marchantia, the sexually formed spore produced a
plant like the parent, after a longer or shorter period of
rest. In Atrichum, however, it grows, not into a plant
like the parent, but into a highly complicated structure,
the fruit or sporogonium, which in its turn forms
asexual spores that produce plants like the original.

This process, k

f g

is less strongly marked in liverworts, and reaches
its height in ferns.

The base of the seta which is thrust into the apex of
the leafy plant, has no organic connection with it, and
while in Atrichum it pulls out with some difficulty, in
many mosses it comes away easily without preparatory
treatment. This feature further emphasizes the dis-
tinctness of the so-called fruit and the parent plant,
from which in quite a parasitic fashion it derives its
nourishment.

6 Icones plantarum, p. 85.

7 Nova Acta A. C. L.-C. Nat. Cur., xviii, p. 791.

8 Sachs, Text-book, 2nd Eng. ed. , pp. 226, 954; Vines, Journal of
Botany, 1879 ; Underwood, Our native ferns and their nllics, p. 35.

A 7 'RICH UM UND ULAT UM. I o 1

The tissues of the seta attain rather higher devel-
opment than those of the stem. The cortical part is
provided with a well formed epidermis, while the axial
part is composed of several tissues, the two portions
being separated by thin-walled parenchyma. At the
apophysis, where the seta expands at its upper end,
many mosses produce stomata quite like those of
higher plants. In rarer instances they occur on the
capsule or seta. Their presence or absence seems to
signify nothing as to relationship, as there is no more

constancy in their occurrence among the highest than
among the lowest forms."

The capsule of Atrichum does not differ widely from
that of other mosses, except in the teeth and epi-
phragm, and otherwise requires no particular explana-
tion. The teeth are composed of groups of cells
arranged as a series of U's placed side by side. In all
other mosses except the immediate allies, where teeth
are present at all, they are formed of the thickened
sides of the cells, and not of whole cells.10 The epi-
phragm, which joins the apices of the teeth like a thitf
membrane, is formed without thickening or special
preparation of the walls. The spores escape by being
shaken from the capsule through the openings between
the teeth, as from a pepper box.

The calyptra, which is the result of the aftergrowth
of the archegonium, was early torn away from its
attachment at the base of the fruit and carried up by
the elongating seta as a hood for the capsule.

9 Valentine, Trans. Linn. Soc. , xviii, p. 239.

10 Sachs, Text-book, 2nd Eng ed., p. 383.

102

MOSS.

The spores germinate by producing a protonema,
which may grow to considerable length, with numerous
branches, before a leafy stem is formed. The successive
inclinations of the transverse walls of the protonema
have been shown to follow the same laws as govern the
successive divisions of the apical cell to form the leafy
stems, so that we are to consider the protonema as an
excessively attenuated stem, from which the leafy stems
arise as lateral branches.

THE MAIDEN-HAIR FERN

Adiantum pedatum L.

PRELIMINARY.

The maiden-hair fern is abundant in dark rich woods
throughout the eastern part of the United States, and
occurs to a considerable extent west of the Rocky
Mountains. It may be recognized with certainty by the
forking of the polished purple leaf-stalk into two equal
recurved branches, which give rise to a number of
straight branches upon one side, bearing the oblong
leaflets. On the back of the leaflets, along their mar-
gins, are born the crescent-shaped fruit dots.

Underground stems and roots (together popularly
called roots), and leaves, including the leaf-stalks, should
be collected when the fruit dots assume a yellowish
brown hue, which is usually about the middle or latter
part of August. The roots should be taken up with
care and the dirt shaken from them gently to avoid
tearing off the root-hairs and root tips, and the clean-
ing completed with water. Part of the leaves and all
of the stems and roots should be preserved in alcohol,
the remainder of the leaves by drying between news-
papers or in a plant press.

The prothallia of Adiantum are less known popu-
larly. They are flat, roundish, green bodies, two

to five millimeters (V,6 to l/6 inch) in diameter,

104 MAIDEN-HAIR FERN.

deeply notched on one edge, and held to the

ground by a cluster of root-hairs from the under

side. They may be found on the surface of

damp ground near patches of the fern, and may be
collected and preserved in alcohol. If a green-house

is accessible, prothallia may usually be obtained
fresh and in quantity from the surface of pots and
earth near which native or exotic species of Adiantum
are growing. If neither source yields suitable material,
the prothallia may be grown by sowing the spores of
Adiantum (to be obtained from the fruit dots on the
margins of the leaflets) on the surface of damp earth
packed smooth and kept at first under a bell-glass in a
good light.1 Strasburger3 recommends sowing the
spores on the surface of a piece of pressed peat (pre-
viously boiled in water to destroy other spores) which
is to be kept saturated with a nutritive solution pre-
pared according to the formula given on page 34. The
peat should be covered by a bell-glass and placed near
a north window. If prothallia of Adiantum can not be
obtained, the prothallia of almost any fern will show
the characteristic features of this stage.

It will be advisable before attempting to cut sections
of the rhizome to soak it for a few minutes in water in

order to soften the tissues somewhat, for when taken
from alcohol they are extremely hard. Care will have
to be exercised in cutting these sections not to nick the
edge of the razor ; it will need frequent sharpening.
Before cutting the sections, the end from which they
are to be cut should be smoothed with a knife.

1 Cf. Campbell, Bot. Gazette, x, p. 356.
3 Das botanische Practicum, p. 457.

ADIANTUM PEDATUM. 105

The requisites for the complete study of this plant
are dried and alcoholic specimens of leaves ; alcoholic
specimens of roots and stems ; fresh prothallia ; alco-
hol ; iodine ; potassic hydrate ; and solution of potassic
chlorate.

LABORATORY WORK

GROSS ANATOMY.

A. GENERAL CHARACTERS. Taking a complete
plant, notice the four parts into which it may be readily
divided :

1. The horizontal, very dark brown, or almost black, un-
der-ground stem, the rhizome, from which are given off

2. A number of slender branching fibers, the roots.

3. The aerial portion, the leaf or frond, consisting of
slender polished stalks, and flat green expansions, the
blades.

4. The appendages to the surface, trichomes, in the form
of scales on the rhizome, hairs on the roots, and repro-
ductive bodies on the leaves.

B. THE STEM or RHIZOME. Notice

1. The size, shape and surface.

2. The occasional branching.

3. The nodes and internodes ; the nodes are indicated by

the growth of a leaf at each, alternately on the right
and left sides ; the intervals between the nodes are the
internodes.

4. The growing apex ; the dying base.

5. The buds near and at the apex. Strip off carefully

io(5 MAIDEN-HAIR FERN.

from several buds the numerous brown scales which
clothe them. Note the two kinds :

a. Buds showing a rudimentary leaf whose stalk is

coiled upon itself, thus :
b. One or more buds whose central part is simply a

continuation of the stem.

6. Make an outline drawing of the rhizome, showing the
size, shape, mode of branching and arrangement of
leaves and buds.

7. The structure. Cut across the rhizome at right angles
to its length and examine the cut surface. Observe

a. The outer ring of brown tissue, the cortical layer.

b. The oval, circular, or Q -shaped white mass, the

fibro-vascular bundle. Where a branch or leaf
arises two fibro-vascular bundles will be seen, thus :
Q ^. Find a part of the rhizome showing such an

arrangement, and trace the course of the bundles
(by cutting a series of rather thick sections) through
at least two internodes, noting the modes in which
successive branches are given off from the bundle.
The smaller Q -shaped portion passes into the
nearest leaf ; the other gradually enlarges, closes
into a circle, elongates into an oval, becomes egg-
shape, and finally opens to form two unequal C's«
the smaller of which soon enters the second leaf on
the opposite side of the rhizome from the first.

c. Inclosed by the fibro-vascular bundle a darker

brown mass not differing otherwise from that sur-
rounding the bundle.

d. Make an enlarged drawing of the cut end of the

stem.

Cut a rhizome longitudinally through the center, and on
the cut surface make out

A DIA N TUM PEDA 7 ' UM. I o 7

e. The parts previously seen in the transverse sec-
tion. Draw.

f. The scales. Mount a few scales from the rhizome,

and note

i. Their shape and texture.
ii. Their structure ; the shape and arrangement of

the cells,
iii. Draw a scale enlarged.

C. THE ROOTS. Notice

1. The shape.

2. Themodeof branching.

3. Their position on the rhizome.

4. The covering of tangled root-hairs with which some are
enveloped.

5. The absence of root-hairs near the whitish growing end.

6. The brownish tip (sometimes torn off), the root-cap.

7. Examine a tran verse section of a root, and compare
with that of the stem. Note the position of the fibro-
vascular bundle. Draw the section.

D. THE LEAF. It may be easily distinguished into two
parts, the stalk, rhachis, with its branches, and the green

blades, pinnules.

1. The main rhachis and its branches. Note

a. The polished surface.

b. The shape ; a little flattened on the anterior sur-
face (i.e., the one corresponding to the upper sur-
face of the leaf). Dried or alcoholic specimens
are likely to have this surface flat or concave while
the posterior remains convex. Note the slight

log MAIDEN-HAIR FERN.

ridges between these two surfaces, more marked
in dried or alcoholic than in fresh specimens.

c. The color of the anterior and posterior surfaces.

d. The branching. At the top the rhachis divides

into two equal (or almost equal) divergent
branches. Each of these again divides into two,
one of which forms the rhachis of a pinna (to be
described shortly), while the other again forks.
Note the number of times such forking occurs and
the relative length of the secondary rhachises thus
formed. Make a diagram showing the above
points.

e. The structure. Cut transverse sections of the stalk

at various heights. Make out the same structure
as detailed for the rhizome. Notice

i. That the brown tissue of the stem is largely

replaced by a whitish one, parenchyma.
ii. The different shape of the sections of the
fibro-vascular bundle at various heights
along the stalk,
iii. Trace its course near the forking of the

stalk until it divides, one-half entering each
branch.

iv. Make diagrams showing these points.
Compare the scales on the base of the leaf-stalk
with those studied from the rhizome.

2. The pinnce. Each pinna is composed of a slender pol-
ished rhachis bearing a number of leaflets, the pinnules.
Note the variation in the number of pinnules on a
rhachis and the general outline of a pinna. Make an
outline drawing of a pinna.

3. The pinnules. Selecting a pinnule near the middle of
the rhachis, observe

ADIAXTUM PEDATUM. 109

a. The shape as to outline and margin.

b. Draw carefully an outline of the pinnule studied.

c. Compare the shape of the terminal pinnule with

those near the middle of the rhachis. Note that
it is like two of the latter joined by their bases.
Compare also the basal pinnules with the middle
ones. Draw an outline of the terminal and basal
pinnules.

d. The surface, texture, and color.

e. The structure. Notice

i. The slender stalk at the angle formed by
the lower and basal edges, attaching the pin-
nule to the rhachis.
ii. The slender branching threads, veins, ex-
tending from the apex of this stalk and
supporting
iii. The green substance of the pinnule, the mes-

ophyll, which fills all the space between the
veins.

The arrangement of the veins, venation. Notice
i. One vein a little stronger than the rest, par-
allel with and close to the lower edge,
ii. The mode of branching.

111. That the veinlets are not connected into a

network.

iv. Compare with the venation of the basal and

terminal pinnules,
v. In the outline drawings of the terminal, basal

and middle pinnules already made draw the

veins.

4. The reproductive bodies. Observe

a. On the upper edges of the under side of the pin-
nules a large number of crescent shaped spots,

no MA I DEN- HA IR FERN.

sort. Note the pinnules from which they are most
uniformly absent.

Soak a pinnule in water for a few minutes and with the
needles turn back

b. The flap which covers a sorus, the indusium. Notice

that it is a portion of the edge of the pinnule
reflexed and peculiarly modified.

c. On the under side of the indusium, a mass of yel-
lowish spheroidal bodies, the sporangia.

Scrape away most of the sporangia from the surface, and

notice

d. The relation of the points of attachment of the

sporangia to the veins. Cut off and draw an indu-
sium showing this.

5. The sporangia. Mount some of the separated sporan-
gia and examine by oblique light. Note

a. Their shape.

b. The short stalk by which they were attached.

c. The ridge, slightly darker than the rest, extending

part way round the sporangium, the annulus.

d. Burst a sporangium and note the contents, minute

powdery bodies, the spores.

e. Study the manner of bursting and scattering the

spores. Tear a bit of an indusium from a dried
specimen previously soaked in water, retaining

a few sporangia ; place it on a slip of glass
and allow it to dry, while watching the sporangia
through a lens, illuminating them from above. A
crack appears on the side where the annulus is
absent, which gapes more and more as the annulus
straightens and becomes recurved. After bending
backward a certain distance, by a sudden jerk
whereby the spores are scattered, the annulus

A DIA NT UM PEDA 7 UM. 1 1 1

becomes straight again (or almost so), and very
gradually resumes the same position as before the
rupture of the sporangium.

E. THE PROTHALLIUM. Examine prothallia of
various ages. Notice

i . The shape and size.

2. The cellular structure, best seen in a mounted speci-
men.

3. The cluster of rhizoids on the under side.

4. That in a prothallium with a young fern plant attached

the plant arises from the under surface.

5. Draw.

MINUTE ANATOMY.

A. THE STEM. Cut a transverse section and examine
with a low power. Make out the following parts :

1. The single outer row of cells, the epidermis.

2. A considerable thickness of brown* thick-walled tissue,

the peripheral sclerenchyma.

3. A circular, oval or Q -shaped mass of whitish tissue,
most of which is the fibro-vascular bundle.

4. Surrounding this bundle, and marking its outline, a
chain-like row of minute oval cells, the bundle-sheath.

5. Entirely or partially surrounded by the fibro-vascular
bundle, a mass of axial sclerenchyma similar to the peri-
pheral.

Examine the section with a high power and study in

3 Yellowish in very thin sections.

"2 MAIDEN-HAIR FERN.

detail each of the tissues and groups of tissues seen above,

in the following order :

6. The epidermis. Observe

a. That the outer wall is thicker than the lateral and

inner ones. In favorable sections a very thin
layer, the cuticle, may be seen covering the outer
wall.

b. That the epidermal cells contain numerous round-
ish or somewhat angular starch granules* Treat a
freshly-cut section with iodine, and notice the
color produced.

i. Study one of the starch grains. Notice the

central lighter spot, the nucleus.6

c. Draw several epidermal cells.

7. The sclerenchyma, peripheral and axial. Note

a. How greatly the walls are thickened.

b. That adjoining walls consist of three or more dis-
tinct layers, the thin central one of which is the

middle lamella.

c. The perforations or pits, which extend through the

thickening layers to the middle lamella at right

angles to the surface of the wall. Observe that

the pits in contiguous cell walls correspond to
one another.

d. Examine the middle lamella at a point where three

or four cells meet. Note that it divides, inclosing
a triangular or quadrangular space which is filled

4 The occurrence of starch in epidermal cells is unusual.

6 The term as here used has an entirely different signification from
that which it has as applied to a cell. Here it denotes a central watery

spot, about which lie the layers of the starch grain, alternately more and
less watery.

ADIA NTUM PEDA TUM. 1 1 3

with a thickening deposit, similar to that of the
inner layers of the wall.
e. The abundance of starch in this tissue.

Draw several sclerenchyma cells showing these

points.

•

8. The cortical parenchyma, lying just outside the bundle-
sheath in some places. Observe

a. That the walls are thin and colorless, with trian-
gular intercellular spaces ; contents of the cells,
granular protoplasm and starch.

b. Compare carefully the middle lamella of the

sclerenchyma with the walls of the parenchyma
where the two tissues merge.

c. Draw several parenchyma cells.

9. The bundle-sheath. Notice the emptiness* of the cells,
their shape, and the position of their longer axes.

10. The fibro-vascular bundle; easily distinguishable into

two regions : first, a central one, the xylem, char-
acterized by the numerous large openings of the

scalariibrm vessels, with small cells, the xylem paren-
chyma, packed between them ; secondly, a peripheral
one, the phloem, showing cells of much more uniform
diameter, and lying between the xylem and the bundle-
sheath. This region contains phloem parenchyma and

sieve cells. Study carefully each of the above
named tissues. Commencing at the bundle-sheath,
examine

a. The phloem parenchyma j composed of two or three

(occasionally but one) irregular rows of small thin-
walled cells next the bundle-sheath and a few cells

6 Sometimes a few starch grains appear to lie in them ; they have been
pulled over by the razor in cutting.

1 1 4 MA IDEN-HA IR FERN1.

here and there between the sieve cells (to be
pointed out directly), all filled with granular pro-

toplasm and small starch grains. Compare with
cortical parenchyma.

b. The sieve cells ; lying between the main body of

phloem parenchyma and the scalariform vessels.
Note their angular shape, slightly thickened walls
and emptiness, except for a little granular material
clinging to the walls.

c. The scalariform vessels. Observe

i. That wherever two vessels are in contact their
contiguous walls are flattened, and the vessels
are therefore irregularly polygonal, having
two or three sides much longer than the
others,
ii. That they are thicker at the angles than on

the sides, and thus appear to be united only
at the angles.

iii. The narrow slit between the contiguous sides

of the vessels.
iv. The emptiness of the vessels.

d. The xylem parenchyma; small cells packed between

the scalariform vessels, and similar ones near their
periphery. Note their contents.

e. Notice the general arrangement of the tissues,

making it a concentric bundle.

Draw sufficient of the fibro-vascular bundle and
its sheath to show the different tissues and their
relations to one another.

Cut a longitudinal radial section of the stem in the plane
of the leaf stalks. Examine with a low power, and make
out

ii. The epidermis.

A DIA AT T UM FED A T UM. 1 1 5

12. The sclerenchyma, peripheral and axial.

13. The double band of whitish tissue, consisting of cortical

parenchyma, bundle-sheath and fibro-vascular bundle.

Examine the section with a high power, studying each
tissue seen in the transverse section.

14. The epidermis; compare the length of its cells with

the same in transverse section. Draw a few cells.

15. The sclerenchyma ; cells elongated with tapering ends.

Note the pits and the middle lamella as in transverse
section. The mouths of the pits may be seen when a
wall extends across a cell. Draw.

16. The cortical parenchyma ; as in transverse section

except that the cells are elongated.

17. The bundle-sheath ; the length and narrowness of the

cells.

18. The fibro-vascular bundle ; the two regions distin-
guished in transverse section, xylem and phloem.
Commencing at the bundle-sheath notice

a. The phloetn parenchyma ; much as in the former

section.

b. The sieve cells ; their great elongation, tapering

ends overlapping succeeding ones, and slightly
thickened walls. Note the sieve plates on the
side walls, looking like irregular thin spots with
fine specks in them; or the sections of them on the
cut edges of the vessels, as depressions of the sur-
face of the wall, paired, one on each side when
two sieve vessels are contiguous.7

c. The scalariform vessels. Observe

ter seen

f e plates may be bet-

1 1 6 MA ID EN- HA IR FERN.

i. That the walls of these vessels present many

narrow thin spaces, looking like slits placed
transversely.

ii. That these thin spaces do not extend entire-
ly across the face of a vessel.

in. Find a place where the contiguous walls of

two vessels have been cut through by the
razor and observe the beaded appearance of
the walls. Each "bead " corresponds to the
thick part of the wall and the intervals to the
thin places.

Isolate some scalariform vessels by boiling a rather thick
longitudinal section for a few seconds in potassic chlorate
solution. Mount in water and examine with a high power 8

iv. The shape and markings. Draw.

d. Draw the fibro-vascular bundle with a portion of

the bundle-sheath.

19. The trtchomes, in the form of scales. Mount scales of

various shapes under the same cover, and observe

a. The shapes and arrangement of the cells, espec-
ially at the apices of the scales.

b. Draw a scale. . .

B. THE ROOT. Cut a transverse section of one of the
larger roots, examine with a high power, and note

i. At the edge of the section (if perfect) the epidermis* of
irregular thick-walled cells, not differing much from

2. The underlying brown parenchyma, which gradually
merges into

8 If the vessels do not separate in mounting, press gently on the cover-
glass with a little sidewise push.

9 So called here because of its position ; not necessarily homologous
with the epidermis of the stem.

ADIA M TUM FED A TUAt. 1 1 7

3. Yellowish sclerenchymay similar to that of the rhizome.
Notice the starch, increasing in quantity toward the
center.

4. Draw a portion of the above tissues.

5. Note the abruptness with which the sclerenchyma joins

0. The fibro-vascular bundle. Notice the sheath which
encircles it.10

a. Just within the bundle-sheath, a row of parenchy-
ma cells with granular contents (protoplasm) ei.cir-

cling the bundle, the pericambium .

b. The xylem region ; consisting of

i. Scalariform vessels ; four (sometimes three or
five) of which, occupying the center of the
bundle, are in pairs, one pair larger than the
other ; the remainder, much smaller, are in
two clusters, one between the vessels of the
smaller pair and the pericambium on each
side. If the scalariform vessels are not easily
made out, a section may be treated with pot-
ash or stained with iodine. They then become
very plain.

ii. Xylem parenchyma; packed between and imme-
diately around the larger vessels.

c. The phloem region ; its two parts separated by

the xylem, lie outside of the vessels of the larger
pair and consist of parenchyma with granular con-
tents and empty sieve vessels.

7. Considering the whole bundle, notice that all the tis-
sues it contains are symmetrically disposed about a cen-
ter. It is therefore known as a radial bundle.

10 The bundle sheath frequently breaks in cutting.

1 1 8 MA I DEN- HA IR FERN'.

8. Draw the bundle.

Take one of the largest roots whose root-cap is present
and cut a series of longitudinal sections, mount, treat with
potash, and selecting the section which passes through the
center of growth, note

9. The concentric layers of the root-cap, each thickest in
the middle, the outer sloughing off.

10. The tissues at the apex of the root. In the center, im-
mediately under the root-cap, a large triangular cell,
apex inward, the apical cell. Notice that the cells
adjacent to the inner faces of the apical cell have evi-
dently been derived from it by partitions parallel to its
faces.

11. Draw the tip of the root, including the root-cap.

12. The trichomes in the form of root-hairs. Slice off from

a root a thin piece carrying a number of hairs, and
note

a. Their attachment to epidermal cells.

b. The shape of a hair near the proximal and distal

ends.

c. The color of the wall and absence of septa.

d. The occasional spiral thickenings in the large hairs,

usually forming a loose spiral of three or four
turns only.

e. The contents.

Draw a hair showing these points.

C. THE LEAVES.

1. The epidertnis. Lift the epidermis of the lower surface
of a leaflet with the point of a needle, seize it with fine

forceps and strip off as much as possible, mount,
examine with high power, and notice

AD I A NT UM PEDATUM. ttg

a. The very irregular shape of the cells and the way

in which they dovetail into each other.

b. Here and there narrow slit-like stomatay each

bounded by two crescentic cells, the guard cells.

c. Along certain lines (over the veins) the different

shape of the cells.

d. The chlorophyll bodies, especially in the guard cells ;

their granular nature.

e. Make a drawing showing these points.

Examine in the same way the epidermis of the
upper surface of a leaflet ; note the absence of
stomata.

Cut a vertical section of a leaflet at right angles to the

veins. Observe

g. On each side of the section the irregular epider-
mis, containing chlorophyll bodies. On a draw-
ing of the surface view of the epidermis draw
imaginary lines in various directions and note
the differing lengths of the lines across any cell.
This will explain the different lengths of the epi-
dermal cells cut by the razor.
//. Occasionally a stoma in the epidermis, bounded

by the two guard cells, communicating with an
intercellular space ; note the shape of the guard
cells.

2. Occupying the space between the upper and lower epi-
dermis, the loosely arranged irregular parenchyma of

* the leaf, mesophyll, also containing chlorophyll.

3. The large intercellular spaces of the parenchyma.

4. At intervals along the section the cut ends of the reins.
Identify the tissues with those seen in the stem.

5. Beneath the vein, forming a part of the lower surface

120 MAIDEN-HAIR FERN".

of the leaf, will be seen three or four very thick-walled
cells.

6. Draw the vertical section of the leaf.

Bend a leaflet over the finger and cut the thinnest possi-
ble slice from the under surface lengthwise of the veins.
Mount with the cut surface upward, and note

7. The length of the cells over the veins and the manner
of overlapping, fibrous tissue. Draw.

8. The trichomes in the form of sporangia. Scrape some
sporangia from a sorus of a dried specimen, examine
dry with a low power, and note

a. The shape and color.

b. The row of brownish walled cells extending part

way around the sporangium, the anmilus.

c. The stalk by which they were attached.
Examine with a high power sporangia from alcoholic

specimens, mounted in water with cover, and note

d. The structure of the wall of the sporangium. This

can be best studied in some of the immature spor-
angia which can usually be found in the same sorus
with the mature. Supplement this study by exam-
ining the wall of a bursted sporangium. Observe
that the wall consists of a single layer of much
flattened cells. Note the nuclei.

e. The annulus. Study the cells which compose it.

Notice that it forms a distinct ridge and is cpn-
tinued beyond the point where the cells are thick-
est by a series of short broad cells with thinner
walls.

The stalk ; the number of cell rows which com-
pose it and the absence of any trace of a fibro-
vascular bundle.

A DIA N T UM PEDA T UM. 1 2 I

g. Draw a sporangium.

//. The place of attachment. Scrape away most of

the sporangia from an indusium, mount it, and
notice the place of attachment of the remaining
sporangia and of the bases of the stalks of the
others. Observe its relation to the vein.

/. The mode of dehiscetice. Tear off a bit of indu-
sium bearing a few sporangia, from a dried speci-
men previously soaked in water, place on a slip
without a cover glass and allow it to dry while
examining it with a low power, illuminating it
from above. Watch the process of bursting care-
fully.

/ The spores. In unbursted sporangia from alco-
holic specimens notice how closely they are
packed. Examine some which have escaped,
and note

i. Their shape and contents.

ii. Their double walls. Burst some spores by

pressing on the cover. In favorable speci-
mens the outer layer of the wall, exospore,
will be ruptured and the delicate inner layer,
endospore, with its inclosed protoplasm will
be seen protruding.

D. THE PROTHALLIUM. Carefully brush away all the
dirt from the under side of a prothallium of medium size
and mount it with the under side uppermost. Examine
with a low power, and notice

i. The shape and the character of the margin.

2. The shapes of the cells. Draw a few cells of the
prothallium showing the various shapes.

3. The abundant chlorophyll bodies.

122 MAIDEN-HAIR FERN.

4. The absence of fibro-vascular bundles.

5. The trichomes in the form of hairs of various

kinds.

a. Shorter or longer pointed hairs on the surface

and margin."

b. Short blunt hairs in like positions.

c. Rhizoids. Note /

i. Their various sizes and lengths,
ii. The irregular shape. Draw.

6. Roundish bodies of considerable size near and
among the rhizoids, the sexual organs.

Examine with a high power, and notice the two sorts :

a. Some bodies spherical and filled with smaller

cells, the antheridia. Observe

i. The single layer of cells forming a wall la

which incloses
ii. A cluster of spherical cells, the sperm cells. ,3
iii. If fresh material is being used, some mature

antheridia will probably have been ruptured
in mounting and the sperm cells with their
anther ozoids have escaped. Note the movements
of the antherozoids after they have escaped
from the sperm cells. Kill them by treating
with iodine, watching them as they come
under its influence. Take note of the body of
the antherozoid, a spirally coiled filament to
which is usually attached an almost anpty

11 Sometimes wanting.

12 Best seen in immature antheridia. All stages may usually be found
on the same prothallium.

13 If the structure of the antheridia can not be made out easily here,
postpone the study till D, 8. a. is reached.

ADIANTUM PEDATUM. 123

vesicle, and of the numerous cilia l4 at the free

end of the body. Draw,
iv. If t no fresh prothallia are procurable the

antherozoid may be seen within the sperm

cell in alcoholic specimens, but its parts are

not distinguishable.
v. Draw both young and mature antheridia,

showing structure and contents.

Ik Some bodies, of similar shape to antheridia but

apparently composed of four cells either quadrant-
shaped and meeting in the middle or somewhat
oval leaving a squarish space between them, the

archegonia.

i. In favorable fresh specimens one or more

moving antherozoids may be seen in the
space, canals between the four cells.

Cut several vertical sections of the prothallium, passing
ihrough the region of the notch and the cluster of rhizoids.
Treat with potash, examine with a high power, and notice

7. The number of cells in thickness of various parts
of the prothallium ; especially its rapid thickening in
the region of the rhizoids.

8. The sexual organs.

a. The globular antheridia, wholly superficial.

Notice the thickness of the wall in mature and
immature ones.

b. The archegonia may be recognized by the more

or less recurved projecting neck composed of
several rows of cells. Note

14 Difficult to see. Use \W

structure

made out now by examining numerous sections of the prothallium.

124 MA IDEN-HA IR, FERN.

i. The number of rows of cells composing the

neck.

11. The canal between the cells of the neck, and

extending from its apex to the imbedded
portion of the archegonium. This canal is
difficult to distinguish unless it contains a
granular substance,
iii. The cluster of cells at the base of the neck

imbedded in the prothallium, the body of the
archegonium.

iv. At the inner end (base) of the canal, in the

midst of the cells of the body, a single large
central cell, filled with a rounded mass of pro-
toplasm, the oosphere.

v. Draw the archegonium.

ANNOTATIONS.

Regarding only the position of organs, perhaps the
most striking difference between Adiantum and Atri-
chum is to be found in the fact that the former has its
leaves only above the ground, while the real stem is
buried below it. In contrast with those low plants
whose rhizoids have served them well enough for hold-
fasts, the fern has developed strong fibrous roots which
ramify widely and perform this office, assisted by the
buried stem. These roots are made necessary not
only by its greater stature and the consequently greater
strains, but by the necessity of wider foraging for the
supply of food. The roots must push their way
among the particles of soil, and, to protect the tender
tissues of the growing point, the tip of the root is
covered by a cap of cells, which arise from segments
cut off from the outer face of the tetrahedral apical cell.

A D1A X TUM PEDA TUM. 1 2 5

As the cap is gradually disorganized and worn away by
contact with the soil it is replaced by new growth from
behind. The root cap is to be considered as a modified
and augmented portion of the epidermis.18

Provision for continued growth of the stem in
length is found in the bud at its apex. The dying
base, however, follows with equal pace the advancing
apex, severing the lateral branches as it reaches them,
which thus become independent plants.

One of the most marked advances upon the structure
of the moss is to be found in'the development of an
extensive and complicated fibro-vascular system. The
simple leaf traces of Atrichum are here replaced by
better developed groups of fibers and vessels to which
the term fibro-vascular bundle is applied. These
bundles are distributed to every part of the plant ; con-
densed in those parts requiring strength, such as the
roots, stem and leafstalk ; diffusely branched in the
leaflets for the support of the chlorophyll-bearing
tissue. Branches of the fibro-vascular bundles having
once been formed, do not reunite with their fellows,
either as a whole or by anastomosing branchlets. The
only organs of Adiantum not reached by the fibro-
vascular bundles are the numerous and unusually
varied trichomes. These are developed as scales
thickly clothing the stem and base of the leaf stalk, as
hairs matted together about the roots, and as sporan-
gia crowded under the edges of the leaflets.

In the growing parts of all organs of the fern, the
cells are parenchymatous, but certain groups early dif-

16 Bessey, Botany, p. 163.

126 MAIDEN-HAIR FERN.

ferentiate into the tissues which compose and surround
the fibro-vascular bundles. These tissues are quite dis-
tinct from each other as well as from the original
parenchyma.

The sheath which incloses the bundles does not
belong to the bundle itself, either in the fern or other
plants, but to the surrounding parenchyma.

The apparently perforated plates on the walls of the
sieve cells can not be seen clearly because of the layer
of protoplasmoid substance which adheres to the walls.
The perforations themselves are not easily demon-
strated though DeBary " thinks he has seen fine fila-
ments connecting granules on opposite sides of a plate.
The continuity of protoplasm between other than
sieve-cells has been demonstrated in many plants.

The arrangement of the tissues of the bundles in
stems and roots is of different types. In the former,
the phloem of the bundle encircles the xylem whence
it is known as a concentric bundle. In the latter,
the xylem forms a plate dividing the phloem into
two portions' which stand one on each side of it.
Assuming a center, the xylem and phloem masses are
symmetrically disposed about it, whence the bundle is
known as radial.18

The root-bundle contains a tissue, the pericambium,
whose cells are still capable of division ; no such
tissue is found in the stem-bundles. New roots have
their origin not in the pericambium as in phanerogams,
but from cells of the bundle-sheath.19

17 Comparative Anatomy, p. 181.

18 Cf. Strasburger, Das botanische Practicum, p. 209 ; DeBary, Com-
parative Anatomy, p. 362.

19 Cf. Strasburger, Das botanische Practicum, p. 276 ; Prantl and
Vines, Text-book of Botany, p. 51.

ADIANTUM FED AT CM. 127

The original parenchyma outside the bundles of the
stem early thickens its walls. These thick walls con-
sist of several layers, the most prominent of which, the
median, is called the middle lamella. This layer,
according to Strasburger80 and others, is the primary
cell wall, upon which thickening layers are deposited.
By other histologists it is held that the layers are
formed, as the thickening progresses, by the differenti-
ation of the wall. Growth in thickness, according to
the first view, is due to apposition ; according to the
second, to intussusception.

The thickening layers of the wall are perforated by
numerous pits, through which probably pass threads of
protoplasm, not occupying the breadth of the pit, but
passing through much more minute openings in the
closing membrane of the middle lamella."

In addition to serving to increase the strength of
the stem, the cortical part is a convenient storehouse
for reserves of food, as indicated by the quantity of
starch in its cells.

The several cell layers of the leaf necessitate some

arrangement for allowing the entrance of gaseous food
and exit of the by-products of the cells' activity ;

hence the loose arrangement of the cells of the leaf,

forming' large intercellular spaces, which communicate

with the exterior by numerous stomata. The stomata

have here the form usual among the higher pteri-

dophytes and flowering plants, an elliptical slit, bounded

by two crescentic cells, which by their change of posi-

80 Bauund Wachsthum der Zellhaute, p. 175.

,l Cf. Schaarschmidt, Protoplasm, Nature, xxxi, p. 290 ; Gardiner,
ibid, p. 390.

128 MAIDEN-HAIR FERN.

tion may either open more widely or almost close the

orifice.

The prothallium, which is developed from a spore
produced by the leaf, bears little resemblance to the
mature spore-bearing fern plant. In its flattened shape,
cellular structure and rhizoids it does, however, have a
striking resemblance to the thalloid stem of Mar-
chantia.

There are thus two distinct stages in the life history
of the fern : one is known as the vegetative, asexual or
pteridoid stage, in which the plant consists of stem,
roots and leaves, and produces spores, and, strangely
enough, answers to the sporogonium of the moss ;
the other, known as the reproductive, sexual or thal-
loid stage,22 in which the plant consists of a prothal-
Hum, on which the reproductive organs are borne, and
corresponds to the leafy plant in the moss.

These reproductive organs are quite like those of
Marchantia and Atrichum. The antheridia consist
originally of one cell, which is later cut up into a cen-
tral cell and several parietal ones. The contents of
the central cell are divided into a number of small
spherical cells in which are formed the antherozoids.
When these are mature the parietal cells absorb water
and burst the apical one, thus permitting the anther-
ozoids to escape. The body of the antherozoid accord-
ing to Strasburger 23 is to be regarded as the proto-
plasm of the nucleus of the sperm cell, and the cilia as

22 Pteridoid and thalloid are terms introduced by Underwood, Our
native ferns and their allies, p. 35.

23 Das botanische Practicum, p. 455 ; Sachs, Text book, 2nd Eng.
ed., p. 423.

ADIANTUM PEDATUM. 129

the peripheral protoplasm of the cell. The vesicle
attached to the hinder coils of the body is formed from
the central or intermediate contents of the sperm cell,
and usually contains some starch grains.

The archegonium is likewise originally a single cell
of the prothallium, which by subsequent division forms
a central cell containing the oosphere, the two canal
cells whose destruction results in the formation of the
canal, the four rows of neck cells and the layer of cells
immediately surrounding the central cell.

The conversion of the two canal cells into mucilage,
and the partial expulsion of this from the canal,
entangles and allows the entrance of the antherozoids,
which by their active movements work their way to
the base of the canal and penetrate the wall of the
central cell in which lies the oosphere. One anthero-
zoid bores its anterior end into the germinal spot of
the oosphere and disappears within it, probably reach-
ing the nucleus. The others lie for some time upon
the oosphere and are gradually absorbed, only one
antherozoid actually penetrating it."

The result of the fertilization of the oosphere is the
formation of a new plant, which remains attached to
the prothallium on its under side for some time* As
the young fern gradually spreads sufficiently, and is
able by means of its leaf and root surface to gather
nourishment for itself, the prothallium, no longer use-
ful, perishes.

Cf. Sachs, I.e.

15 Strasburger, op. cit., p. 458

♦

SCOTCH PINE

Pinus sylvestris L.

PRELIMINARY.

THE Scotch pine is a species commonly planted for
ornament. It may be readily recognized by the follow-
ing characters. At a short distance the tree has a
grayish-green color. The leaves are in pairs, five to
ten centimeters (two to four inches) long, somewhat
twisted, covered with a whitish powder which can be
rubbed off with the fingers and to which the peculiar
color of the tree is due. The cones are small, about
five centimeters (two inches) in length, the free ends of
the scales being produced into conspicuous protuber-
ances, which near the base of the cone are recurved.

The Austrian pine, a two-leaved species also com-
monly planted for ornament, differs from the preced-
ing in having longer leaves — from ten to fifteen centi-
meters (four to six inches) in length — with a dark green
color without any of the powder. The cones are much
larger and without the recurved protuberances. If
the Scotch pine can not be procured the Austrian will
do quite well, being closely similar to it in structure.

The flowers, both male and female, should be col-
lected in spring as soon as the male flowers begin to
scatter their pollen. The male flowers when mature

PI 1ST US S YL VE S TRIS. I J I

form conspicuous yellow clusters at the base of the
young shoots. The female flowers are quite inconspic-
uous, in small oval clusters of a pinkish color, project-
ing slightly beyond the ends of the young shoots.
The tree bearing abundant male flowers usually bears

few female ones, and vice versa. These flowers when

collected should be preserved in alcohol. A few weeks
Liter the two-year-old cones, which will be found just
below the new shoots, should be collected and pre-
served in alcohol. If the plant is to be studied in
spring or summer, some of the large terminal buds
should be collected in the late autumn, winter or early
spring preceding, and preserved in alcohol. Leaves and
stems should be gathered about the first of July, and
preserved in alcohol. Mature cones should be gathered
in winter or early spring and allowed to dry, care being

taken to prevent losing the seeds, which will shake out
on drying.

Fresh leaves and stems may be used for the study
of the gross anatomy, but if used for the minute
anatomy it is well before cutting sections to place them
in alcohol for a few days to get rid of the resin which
exudes and gums the fingers and knife unpleasantly.

Before cutting sections of stems or leaves which have
been preserved in alcohol and before dissecting the male
and female flower clusters, it is well to place them for
a day in a mixture of equal parts of alcohol and
glycerine, which renders them somewhat easier to
manipulate. They may, however, be used direct from
the alcohol.

The requisites for the complete study are stems,

1 1 2 SCO TCH PINE.

leaves, terminal buds, male and female flowers, year-
old and two-year-old cones, preserved in alcohol ;
mature cones and seeds, dry ; alcohol ; potash ; glycer-
ine ; sulphuric acid ; and if convenient, magenta ;
methyl blue ; and chlor-iodide of zinc.

LABORATORY WORK.

GROSS ANATOMY.

A. GENERAL CHARACTERS. Note

i. The central axis or stem; its few main branches and.
numerous very short dwarf branches l bearing

2. Pairs of very slender elongated green needle leaves.

3. The scales upon the stem, those covering the buds at
the apex of the stem and those overlapping the bases of
young leaves. All may be called scale leaves.

4. Near the base of the young shoots in some specimens,
a number of oblong (nearly globular) clusters of light
yellow bodies, stamens, the male flowers ; in other

■

specimens, one or two small oval clusters of female
flowers , projecting beyond the end of the stem.

B. THE STEM. Examine

1. The surface of a year-old shoot. Note the scales
covering it, especially near the base of the shoot.
Compare with the surface of older stems ; note the
gradual obliteration of the scales.

2. The arrangement of the main brnches? Note the

1 The terms " dwarf branches " or "dwarf shoots" will be used to
distinguish these from the main branches or shoots. (The term shoot
includes the branch with its leaves.)

2 Best seen in specimens from young vigorous trees. If possible the
student should study the tree itself.

PIN US S YL VES TRIS. 1 33

number of branches and the relative vigor of terminal
and lateraUshoots. Compare also, as to size, the buds
found in clusters at the apices of the branches.

3. The arrangement of the dwarf branches. Select the
straightest and most vigorous year-old branches for
this study. Notice

a. The position of the branches relative to the scales.

b. Their absence from certain portions of the stem.

c. Pull out the pairs of leaves from fifteen or twenty

consecutive branches. Stick a pin at the base of
any branch, and then find a branch that stands
directly above this one. Count the number of
branches between these, including the first. This
number will be equal to the number of vertical
ranks in which the branches stand.

d. Make a diagram in the following manner, to show

the relative position of the branches : draw lightly
a number of concentric circles about three milli-
meters apart (the number should be twice as
many as the number of vertical ranks, plus one).
Divide the outer circle by as many equidistant
points as there are vertical ranks of branches.
From these points draw radii, lightly. Take a
piece of straight stem about ten centimeters long
which has been stripped of its leaves. Mark the
position of three or four consecutive branches by
pins, so placed that if pressed in they would pass
through the center of the stem. Fasten the lowest
pin securely. Make a mark on the outer circle at

any radius to indicate the position of the branch
marked by the lowest pin. Erect the stem at
the center of the circles, making the lowest pin
coincide with this radius, and mark the next

134 SCOTCH PINE.

higher branch on the second circle at the radius
with which its pin now most nearly coincides. Mark
the third and fourth in the same way. Leaving
the lowest pin in place, move the pin next lowest to
the next higher unmarked branch, and mark its
position. Repeat this until all the circles are
filled, numbering each branch from the lowest up.
Studying this diagram determine

i. The arithmetical difference between the numbers

of the branches which lie on the same radius.

ii. The number of turns made by a spiral line

joining successive branches, i, 2, 3, 4, etc.,
until it reaches a branch over the first.

iii. Find a fraction which will express the part of

a circle intervening between any two suc-
cessive branches.

iv. Note that the numerator of this fraction ex-
presses the number of turns made by the spiral
line, and the denominator the number of ranks
in which the leaves stand.

4. The buds. Notice

a. Their position and relative size.

b. Their shape.

c. Their structure. Study

i. The scales. Carefully strip them from the bud
with needles. Note particularly the character
of the edges and the differences between the
apical and basal portions. After removing the
brown apical portion, the green basal parts
will be seen closely investing

ii. The axis. Bisect longitudinally the portion

of the bud remaining. Observe in the center
the whitish stem or axis, tapering gradually

PIX US S YL VESTRIS. 135

and then rapidly to a point, and bearing the
thick-set bases of the bud scales, in the axils
of which may be seen
iii. Secondary buds.3 Take out one of these buds

carefully and dissect it. Note the scales which
cover it. By cautiously removing these the

rudimentary needle-leaves, looking like two

minute knobs, may be found, apparently at
the end of a very short stem to which the
scales were attached.

iv. Make drawings showing the external appear-
ance and structure of the buds, both main
and secondary.
d. Compare the buds with the branches. Observe

that a bud is simply an undeveloped branch.

5. The structure. Cut an old stem square across to study
the cut surface. Mount also a transverse section of
the same. Notice

a. A central yellowish or brownish spot of irregular

outline, the pith.

b. Surrounding the pith a zone of firm tissue, the

wood. Observe

i. The concentric masses of tissue, growth rings,

the number depending upon the age of the
shoot at the point cut. In thin parts of the
section, notice the difference between the
central and peripheral portions of any growth
ring,
ii. The many fine radiating lines, the medullary

rays. Note the extent of the larger ones,
iii. Many small scattered openings, the resin ducts.

8 These can only be found of sufficient size to dissect in buds collected
late in autumn or in early spring just before they begin to expand.

I36 SCOTCH PINE.

iv. In some sections one or more distinct whitish

bundles passing out from the center of the
stem. Notice that a continuation of the cen-
tral pith occupies the center of each. Observe
the relation of these bundles to the scars on
the bark indicating the position of former
dwarf shoots. If the stem be four or more
years old, note that the bundles stop quite

abruptly at the close of the second year's
growth.

c. All the part outside the wood, the bark. Distin-
guish its three layers :

i. The inner fibrous layer, whitish. Notice its
appearance and thickness relative to the
whole bark.

ii. The middle, green layer. Notice the large

resin ducts. (In fresh specimens note the
color, consistence and odor of the liquid they
exude.) Compare the thickness of this layer
with that of the first.

iii. The outer brownish layer, except in quite old

stems made by the adherence of the bases of
the scale leaves. Note its relative thickness.

iv. Strip off a portion of the bark. The three

layers may be easily separated with the

fingers. Study the characteristics of each.

d. Bisect the stem longitudinally. On the cut sur-
face and in thin sections make out the pith, wood
and bark ; the growth rings, medullary rays, and
bundles extending toward bases of former leaf-
branches, in the wood ; the three layers of the bark.

e. Make drawings of the transverse and longitudinal

sections to show completely the structure of the
stem.

PIN US S YL VES TRIS. 1 3 7

6. The dwarf shoots. Carefully break one from the stem,
and note

a. The scales (scale leaves) enwrapping it and the

bases of the needle leaves. If possible compare
these scales on young and old dwarf shoots.

b. The length.

c. The very small rudimentary terminal bud between

the leaves. This is best seen on the dwarf shoots

from young vigorous trees. It is minute or
absent on others.

C. THE LEAVES.

1. The scale leaves. These have already been studied as
they occur on the dwarf shoots (B. 6. a.) and in the bud
(B. 4. c. i.). Compare the scales of the stem with those of
a young bud and notice the loss of the deciduous apex.

2. The needle leaves. Note

a. The number on each dwarf branch.

b. The shape and apex ; also the shape of the trans-
verse section. Draw a leaf.

c. The color. Compare old and young leaves if

possible.

d. The texture ; firmest near the apex, softer near

the base, due to basal growth. These points
are especially noticeable in young leaves.

e. The edges. Draw the finger from the apex toward

the base. Examine with a lens.
The surface. Observe

i. That it is faintly whitened {glaucous) by a

powder which can be removed by drawing the
leaf through the fingers ; best seen on the
flat side.

1 3 8 SCO TCH PINE.

ii. The longitudinal rows of whitish dots on both

surfaces. Cut a thin slice from the convex
surface, mount, and examine by transmitted
light. If sufficiently thin, the dots will now
be seen to be minute openings, the stomata or
breathing pores.4
g. The structure. Cut a transverse section and

examine by transmitted light. Notice
i. Occupying the center an oval patch of whit-
ish tissue, the fibro-vascular region.

ii. Outside the central whitish area, compact

green tissue, mesophyll. In this zone notice a
dozen or more openings, the resin ducts.

iii. Enveloping the whole, the narrow colorless

cortical area.
iv. Draw the section.
Cut a longitudinal section parallel to the flat side. Make
out the same regions as in the transverse section.

D. THE FLOWERS.

i. Male or staminate. Carefully break off one of the
clusters.

a. Note the short stalk by which it was attached to

the stem.

b. Note that the cluster is made up of numerous

short-stalked bodies, the stamens, attached to an
axis. Each stamen consists of a flat scale bearing
on the inferior surface two enlargements, the

pollen sacs.

c. Burst a pollen sac. Note the innumerable minute

grains of pollen which escape.

4 More accurately, the external chambers of the stomata, for the real
stomata are deep seated.

PIN US S YL VESTRIS. 1 3 9

d. Find a stamen which has burst spontaneously.

Note how it is ruptured (by slits).

e. Note the arrangement of the flowers? They are

almost sessile and crowded on an elongated axis
forming a spike. Notice the scale subtending
each flower, and the number and position of the
scales attached to the short stalk of the flower.
Note the position of the flowers ; each replaces a
branch on the young shoot.

g. Draw a stamen showing its structure.

2. Female or pistillate. Taking a single cluster, a spike,
notice

a. The stalk, peduncle, by which it is attached ; its

direction ; the scales on the peduncle.

b. That it is composed of two kinds of scales : (1)

thin, the bracts ; (2) thick, the carpellary scales.

Dissect out a single bract ; note

i. The texture and shape.

ii. Draw the bract.
Dissect out a single carpellary scale ; note

iii. The shape and texture.

iv. The prominent keel on the upper surface in

the median line.

v. Two enlargements on the superior surface,

near the proximal end, the ovules. Notice
the position of the ovules and the large ori-
fice at their free ends, the micropyle, the
integument of the ovule being prolonged into
a short tube, whose right and left sides are
still further produced into two short fila-
ments.

5 It is assumed that each cluster of stamens constitutes a single flower.

i 40 SCO TCH PINE.

vi. Draw a scale showing all these points.

c. Difference in the size of bracts and scales in differ-
ent parts of the same cluster.

d. Position of the cluster ; replacing one of the

main branches.

Examine a year-old cone. Bisect it vertically, and note

e. The central tapering axis.

The cut edges of the scales and bracts. Observe
the relative thickness of the scales at their proxi-
mal and distal ends.

g. The ovules appearing in section at the base of the

scales.
h. Whether the scales are free from each other or

adherent.
i. Draw the cut surface.
Dissect out a scale with its ovules. Notice the many scales
with abortive ovules. Bisect a well developed ovule care-
fully, through the micropyle. Note

j. The diminished size of the micropyle.

k. The single i?itegument.

I. That portion inclosed by the integument, the

nucellus.

m. Nearest the base of the nucellus (the end nearest

the micropyle being considered the apex) a large
cavity, the embryo-sac, partially or wholly filled
with a soft substance, the endosperm.

n. Draw the cut surface of the ovule.

E. THE FRUIT (CONES). Examining a mature cone,
notice

1. The large carpellary scales, making the bulk of the cone.
Observe their color, above and below, consistence, shape
and markings at the free ends.

2. In an open cone, or by cutting away the basal third of

PIN US S YL VESTRIS. 1 4 1

a closed cone, the smaller bracts subtending the carpel-
lary scales.

3. Closely applied to the superior surface of the carpellary
scales, a pair of thin wing-like scales, each bearing at its
proximal end a perfect seed or an abortive ovule,

4. The seed. Note

a. The shapey surface and markings.

b. At the pointed end notice the minute opening, the

micropyle.

c. The structure. Bisect the seed longitudinally par-
• allel with the flatter faces, and in the halves make

out

i. The firm coat.

ii. The inclosed portion consisting of two parts :

(1) the young plantlet, embryo, lying in the

axis ; (2) the food for the plantlet, endosperm?

iii. Note the position of the embryo with respect

to the micropyle.
Take another seed and with needles dissect off

iv. The coat. Notice that it has differentiated

into two layers. Compare the two as to
color, thickness and strength.
Dissect the endosperm carefully from the embryo. In the
atter make out

v. The short stem, caulicle.

vi. The six divisions arising from about the apex

of the caulicle, the first leaves, cotyledons.

vii. A minute elevation in the midst of the coty-
ledons, at the apex of the caulicle, the rudi-
mentary terminal bud, plumule. (Not easily
seen.)

6 The endosperm has therefore entirely displaced the nucellus originally
surrounding it. (See D. 2. /. and m.)

1 4 2 SCO TCH PINE.

MINUTE ANATOMY.

A. THE STEM. Cut a transverse section of a year-old
stem, examine with a low power and note

i. The pithy occupying the center of the section.
Observe

a. The outline of the pith.

b. In some sections a portion extending outward to

enter a dwarf branch. The salient angles of the
pith are all due to such outward extensions at
different heights.

c. The loose arrangement of its cells.

2. The wood [xylem). Observe

a. The arrangement of the cells.

b. The openings of the resin ducts.

c. The division into two zones, growth rings.

3. The cambium ; a narrow, cloudy looking zone, bound-
ing the xylem. (If the section be from a stem gathered
in winter or early spring, the cambium zone will be
indistinguishable.)

4. Thephloem ; of compactly-arranged cells, with a whitish
appearance.

5. The cortical parenchyma ; outside the phloem, consisting
of large, loosely-arranged cells, which in sections of a
fresh stem contain much chlorophyll. In this region
note the large oval openings of resin ducts.

6. Dark lines from the pith to the cortical parenchyma,
the medullary rays.

7. The edge of the section. The cortical parenchyma is
bounded by a row or two of small close-set cells. All
the tissue beyond this belongs to the bases of the scale
leaves, which cover the stem.

PINUS SYLVESTRIS. 143

Examine with a high power and study

8. The pith parenchyma. Note

a. The shape and arrangement of the cells ; the modified

shape of those passing out to a dwarf branch.

b. The contents. Test with iodine.

9. The xylem. Notice that the salient angles of the pith
divide it more or less completely into wedge-shaped
bundles. Studying one of these wedges, note

a. At the apex one or two resin ducts. Study their

structure, noticing

i. The shape of the opening,
ii. The circle of rather delicate cells lining the

duct, the secreting layer. Note the granular
nucleus in each, nearly filling the cell.
Hi. The quite irregular circle of flattened cells,
' with longer diameters parallel with the circum-
ference, bounding the duct, the sheath.

b. Between the resin duct and the pith, forming the

point of the wedge, a group of several spiral and
reticulated vessels. These are rather difficult to
distinguish from the wood cells. They may be
recognized by their slightly thicker walls, the
smaller diameter and rounder shape of their
cavities. On staining the section slightly with
magenta, they take a somewhat deeper color than
the wood cells. After the section has lain for some
time in glycerine they may be recognized by their
greater opacity.

c. Forming the bulk of the xylem, the wood cells or

fibers. On account of the similarity of the mark-
ings (to be studied later) on their walls to those on

tracheae or vessels, they are called tracheides.
Note

1 44 SCO TCH PINE.

i. Shape and arrangement.
ii. Their emptiness.

iii. Their thick walls, showing in thin parts of the

section, a middle lamella.

iv. In the thinnest part of the section, search for

places where the radial walls 7 of contiguous
cells bow away from each other like two watch
glasses placed with concavities together.
They are most readily found in the youngest
part of the xylem. In the most favorable
sections these bowed walls may be seen to be
interrupted at their points of greatest diverg-

ence thus -<">-. These are sections of the

bordered pits (further described at A. 18. b.

iii.).
v. Compare the tracheides of the outer growth

ring with adjacent ones of the inner one.

■

vi. Wide one-sided bordered pits where the

tracheides adjoin the cells of the medullary

• rays.

10. The cambium. Note

a. The radial rows of rectangular,8 very thin-walled

cells, passing abruptly on the one hand into the
xylem, but shading almost imperceptibly on the
other into

ii. The phloem. Note the two elements which compose

it:

a. Angular thick-walled cells with a whitish luster

and constituting the greater part of the phloem,
the sieve cells. In favorable sections the radial

V. e. , those lying along a radius of the stem
8 Very apt to be distorted in cutting.

PIN USSYLVES1 RIS. 1 4 5

walls of some of these cells will be found perfor-
ated by clusters of very fine pits, looking like
fine parallel lines passing across the wall. These
are sections of the sieve pla tes ; they occupy the
same relative position as the sections of the bor-
dered pits of the tracheides. Note the shape of
the sieve cells next the cambium and next the
cortical parenchyma.
b. Near the periphery of the sieve tissue an inter-
rupted row of cells with brown or yellow contents
in which are strongly refringent crystals. Near
the cambium a similar row of cells, larger and
rounder than the sieve cells and with colorless or
slightly yellowish homogeneous contents, in which
a small crystal or two may sometimes be seen.
These two broken rows of cells are the phloem-
parenchyma?

12. The cortical parenchyma. Note

a. The shape, size and arrangement of the cells. Com-
pare with pith parenchyma.

b. The contents.

c. The very large resin ducts. Compare their struct-
ure with those of the xylem (A. q. a.). Note the
cells of the sheath, larger, thicker-walled and not
flattened as are those surrounding the ducts in the
xylem ; the secreting cells, similar to but more
numerous than those of the xylem ducts.

13. The medullary rays. In a thin part of the section

note

a. Their extent, from pith to cortical parenchyma.

9 Can be brought out by staining with chlor-iodide of zinc and better
still by methyl blue.

1 46 SCO TCH PINE.

■

b. The shapes of the cells in the xylem and the grad-
ual transition into the cortical parenchyma.

c. The contents of the cells.

14. The bases of the scale leaves. (As they are closely

attached to the stem, and the lower portions not dis-
tinguishable from it, their transverse section is most
conveniently studied at this time.) Note the two
layers :

a. The inner ; cells very thin-walled and irregular,

apt to be distorted in cutting.

b. The outer ; composed of one or two rows of large

cells, sclerenchyma (note shape), and a single outer-
most row of smaller cells, the epidermis. Note

i. The thickening of the outermost wall of the

epidermis.

ii. The continuous layer covering this wall, the

cuticle.

15. Draw a part of the section, filling in sufficient to show

the structure completely.

Cut a longitudinal radial section of a year-old stem.
Examine with a low power, and make out

16. The same areas as seen in transverse section, in this

section appearing as strips :

■

a. The pith ; its regular margins.

b. The xylem. Note

i. Patches* of transversely placed cells, the

medullary rays.
ii. The resin ducts ; showing as one or two lighter

streaks in the xylem.
iii. The two growth rings.

c. The cambium ; a very narrow whitish strip.

d. The phloem ; compact and fibrous-looking.

e. The cortical parejichyma.

PINUS SYL VESTRIS. 147

The scale haves.
Examine with a high power. Study

17. The pith cells. Note

a. The shape and arrangement.

18. The xylem. Note

a. Near the pith parenchyma a cluster of spiral and

reticulated vessels. Notice the irregularity and
closeness of the spiral thickening.

b. The trac/ieidest making the bulk of the xylem.

Note
i. Their shape. Observe their ends.

ii. Their thickened walls.

iii. Their markings, bordered pits. In the young-
est part of the xylem study the structure of one
of these pits. Observe the two concentric
circles they present. Note which is more dis-
tinct. Compare with transverse section and
discover the cause of this appearance. The
outer circle is at the point where, in section
see diagram at A. 9. c. iv.) the arms of the
Y diverge from its stem ; the inner is the
edge of the opening in the bowed walls. By
examining this section thoroughly, chance
sections of the pits may be found which will
further elucidate their structure.

iv. The size of the pits compared with the breadth

of the fibers, and their arrangement on the
fibers.

v. The large thin spots on the walls of the cells

of the medullary rays, where they join the
adjacent tissues.

c. Between the tracheides and the spiral vessels a

few intermediate cells with plain pits nearly or

1 48 score// P/NE.

quite as large as the bordered ones of the trach-
eides. By focusing carefully the walls of these
cells may sometimes be seen in section.

19. The cambium. Note the shape and contents of the cells.

There is sometimes difficulty in discovering the end
walls of the cambium cells. It can be obviated some-
what by examining a section which has lain in glycerine

for a few hours. Notice particularly the delicacy of
the walls.

20. The sieve cells. Study

a. Their shape and arrangement.

b. The markings on their walls ; round or oval areas

of fine perforations, looking like minute specks.
Note their arrangement ; compare with that of the
bordered pits on the tracheides.

21. The phloem parenchyma j note length and contents of

the cells.

22. The cortical parenchyma.

a. Study the shapes and contents of the cells.

b. Notice here and there cells which seem to have

been divided by a partition, the pair still retaining
an oval shape.

c. The large intercellular spaces.

23. The medullary rays. Study their cells in the cambium

and sieve cell regions.

24. The resin ducts. (Their longitudinal structure may be

studied either in the longitudinal or transverse section
of the stem, the latter usually showing a longitudinal

10 Difficult to distinguish without staining with methyl blue or chlor-io-
dide of zinc.

pry US SYLVESTRIS. 149

section of one or more of the horizontal branches con-
necting neighboring ducts. The structure is most
easily made out in those of the xylem, those of the
phloem being too large to allow a complete section to
be easily obtained.) Note

a. The empty cells forming the sheath ; their shape.

b. The secreting parenchyma cells lining the duct ;

shape and contents.

25. The bases of the scale leaves. Note

a. The delicate thin-walled cells forming their inner

portion.

b. The rather thick -walled cells, sclerenchyma, form-
ing the outer part.

c. The very thick- walled outer row, the epidermis,

with thickly pitted walls.

d. The very thick cuticle.

e. The contents ; note color.

26. Draw a portion of the section, showing all the above

points.

Cut a longitudinal tangential section, passing through
the wood. Examine with a high power, and note

27. The cut ends of the medullary rays, wedged between

the fibers of the xylem. Notice

a. The number of rows of cells in the thickness and

height of each ray.

b. The thin parts of the walls corresponding to the

pits (see A. 18. b. v.).

c. Make a drawing of one of the rays, showing also
a few adjacent tracheides.

28. The numerous sections, in different directions, through

bordered pits. Study these sections further, if necessary
to an understanding of the structure of the pits.

1 5 o SCO TCH PINE.

29. The very tapering ends of the tracheides.

Cut transverse and longitudinal sections of a young stem
collected at flowering time. Examine with a high power,
and compare with similar sections of the older stem. Notice
the walls and contents of the cells of the several tissues
and particularly

30. The distinctness of the spiral and reticulated vessels.

31. The deep indentations of the margin of the stem in

transverse section, marking the breadth of the scale
leaves.

32. The simple epidermal and hypodermal tissues consti-
tuting the bases of the scale leaves.

Strip off the brown apical portions of the bud-scales from

■

a winter bud and bisect it longitudinally a little to one side
of the center. Cut a series of longitudinal sections as uni-
formly thin as possible, until the center of the stem has been
passed. Mount every section, treat with potash and exam-
ine with a low power. Search for the section which
includes the center of the axis. It may be recognized by

■

the conical shape of the apex. Note

^^. The central axis or stem.. Observe the arrangement

of the cells.

34. The buds on the side of this axis. Notice

a. The large scale (base of bud scale) subtending

each. .

b. The central rounded mass of cells, an undevel-
oped dwarf branch, covered in by scales. Search
for a bud whose central part shows three rounded
protuberances. These are the two leaves with the
terminal bud of the dwarf branch between them.

Draw.

PIN USSYLVES T1US. J 5 1

35. The conical apex, growing point, of the axis. Not

the scales which cover it.

Examine with a high power. Study both the growing
leaves and the apex of the stem. Note

36. The shape of the cells, which in these regions are cap-
able of division and are collectively known as the

primary meristem.

37. A short distance behind the growing apex, the cells of

the primary meristem become differentiated, some
becoming elongated and fusiform and others forming
the spiral vessels. Trace them further and further from
the growing point and notice that the differentiation
constantly increases.

38. On the sides of the section, just behind the conical

point, one or two elevations, the apices of the axes of
lateral buds of the succeeding season. Draw the
apex.

B. THE LEAVES. Cut a transverse section of one of
the older needle leaves below the middle. Examine with a
low power, and note

1. The shape of the section.

2. The three distinct regions it presents :

a. The narrow outer cortical region, whitish in color.

b. The central oval fibro-vascular region, bounded by

a distinct chain of cells, the bundle sheath.

c. Between these two regions, a zone of green (green-
ish even in alcoholic specimens) parenchyma, the

mesophyll.

3. The number and position of the resin ducts.

4. Make a sketch of the section.

152 SCOTCH PINE.

Examine with a high power, and study

5. The epidermal cells. Note

a. The very thick walls, their cavities nearly or quite

obliterated. The outer layers of this thickening
are cuticularized.

b. The cuticle, quite thick and dipping as a thin

wedge between the cells.

c. The crack-like pits radiating from the cavity.

d. The enlargement of the cell which forms the corner

of the leaf.

e. The stomata. Study their structure carefully,

noting

i. The peculiar shape of the epidermal cells

above the stoma, the outer wall, about as
thick as the adjacent cells of the epidermis,
prolonged upward to form a ridge overarch-
ing the outer chamber of the stoma. Observe
the cavity of these cells, much larger than
those of adjacent cells. At the bottom of the
outer chamber,

ii. The guard cells, their shape and the thicken-
ing of their outer walls.

iii. The large intercellular space beneath the

guard cells, the inner chamber of the stoma.

6. The usually single, in places double or triple, row of
small cells underneath the epidermis, the hypoderma.

Note

a. The shape, and the thickness of walls.

b. Where the greatest number of cell-rows occurs.

c. The well-defined middle lamella.

d. That the hypoderma is interrupted at each stoma.

7. Draw a stoma with a few of the adjacent epidermal
and hypodermal cells.

PIN US S YL VESTRIS. 1 5 3

8. The mesophyll. Note

a. The shape of the cells, and the number of rows

between the hypoderma and bundle sheath.

b. The infoldings of the wall, dividing the cavity

into recesses. Observe the position of the most
prominent of these infoldings in the outermost
row of mesophyll cells. Observe occasionally
(usually near a stoma) branched cells. Deter-
mine the relation of these to the cells with simple

infoldings.

c. In fresh specimens, the abundant chlorophyll.

d. The resin ducts ; compare their structure with

those of the stem. Notice the thick walls of the
cells of the sheath.

9. Draw a few mesophyll cells showing also a resin duct.

10. The fibro-vascular region. Study

a. The bundle sheath ; shape and contents of the

cells.

b. The two masses of small cells, the fibro-vascular

bundles, somewhat separated from each other and
obliquely placed. Note the well-marked division
into two areas :

i. The xylem, next the flat side of the leaf,
consisting of spiral and reticulated ves-
sels and tracheides, arranged in radial rows.

ii. The phloem, next the convex side of the leaf,

consisting chiefly of undeveloped sieve cells.

iii. The radial rows of parenchyma (like medul-
lary rays), passing through both xylem and
phloem.

iv. In the xylem area, occasionally a poorly

developed resin duct.

154 • SCO TCH PINE.

v. Draw one of the bundles.

c. Between the bundles and more or less encircling

them, especially next the convex side of the leaf,
fibrous tissue consisting of large thick-walled cells
with small cavities.

d. On the side of the bundle pair toward the flat

side of the leaf, large thin-walled, mostly empty cells.

e. Filling the remainder of the fibro-vascular region

and entirely encircling the parts named, large
tracheides resembling the preceding, but with more
or less conspicuous contents, and walls marked
with bordered pits. Compare the markings with
those of the tracheides of the stem, studying both
face and section views.

Draw a few cells of each tissue named outside the

bundles.
Cut a longitudinal section through the central part cf the

leaf. Examine with a high power, and study
ii. The epidermis. Note

a. The shape of the cells. Unless the section be quite

thin, the epidermis will appear as a continuously
thickened border of the section. The end walls of
the cells are hard to make out, even in the best
sections.

b. The irregular cavity, and innumerable pits which

perforate the thickening layers.

c. If a number of sections be made, one or more will

traverse a line of stomata. Note the shape of
the outer chamber, the shape of the guard cells,
and of the intercellular space below.

d. Draw a stoma and the adjacent cells.

12. Underlying the epidermis, the elongated sclerenchyma

cells, the hypoder ma. In sections passing through a

PIN USSYLVES TRIS. I 5 5

line of stomata, note the absence of any hypoderma,
except short cells between the guard cells of adjacent
stomata.

13. Draw a few cells of epidermis and hypoderma.

14. The mcsophyll. Note how loosely it is arranged, with

an intercellular space between the rows of cells, enlarg-
ing under each stoma. Note also the shapes of the
cells, the apparent absence of infoldings in this view,
and the number of cells in each row between the bun-
dle sheath and hypoderma. The determination of the
latter point will need close inspection and careful
focusing. The infoldings seen in transverse section
are now seen as apparent partitions increasing the
apparent number of cells above the actual. In places
none of these false partitions occur, and the real number
of cells may be easily noted. Draw a few rows of meso-
phyll cells.

15. The resin ducts ; note the sheath cells, elongated and

thick walled ; the secreting cells, with thin wavy walls
and prominent nuclei. Draw.

16. The fibro-vascular region. The various tissues of this

region appear as strips in this section.

a. The bundle sheath ; a. row of elongated cells next

the mesophyll. Draw.

b. The tracheides, on both sides of the bundles ;

note the shape and markings of the cells.

c. Note the change in shape where this tissue adjoins

the fibrous tissue, the cells becoming much elon-
gated. Draw, showing both forms.

d. The fibrous tissue ; greatly elongated thick-walled

fibers with tapering ends, next the tracheides.
Draw.

1 5 6 SCO TCH PINE.

s. Next the xylem, large thin-walled mostly empty

cells.

■

/. The phloem j consisting of thick-set, very long

cells, with slightly oblique ends, usually crowded
with protoplasm and containing large nuclei.
Draw.

g. The xylem j note

i. Tracheides like those of the stem but poorly

developed, with few markings,
ii. Spiral vessels like those of the stem ; var-
iously placed with respect to the tracheides.
Cut the thinnest possible slice from the surface of an old
leaf and then cut a thin section from the same place.
Mount both with the outer surfaces upward and examine
with a high power. Studying the first, the slice of epidermis,
note

17. The arrangement of the stomata.

18. The two kinds of epidermal cells, those lying near and

in a line of stomata and those lying between the lines
of stomata ; observe the shapes. In the former note
the ridge formed by the upturned edges of the six cells

■

which bound the stoma.11 If this cannot be readily
made out, treat the specimen with potash and observe
again in a few minutes. Draw a few cells of each.

In the tangential section from beneath the epidermis,
note

19. The cut ends of the mesophyll cells ; shape and arange-

ment. Draw.

11 The student should not mistake the peripheral border of the ridge
for the outer wall of the six cells. The cells mentioned are quite large,
the central ones extending from one stoma to another and the others us-
ually half that distance.

PIN US SYLVES TRIS. 1 5 7

20. The guard cells of the stomata also may usually be

seen. Draw.

Cut a transverse section of the base of a young leaf, col-
lected at flowering time.

21. Compare with the transverse section of an older leaf.

Note the presence of protoplasm in almost all the
tissues, completely filling the cells. Clear with potash.
Compare carefully each tissue with the mature form,
noticing particularly the lack of differentiation of the
tissues, especially in the fibro-vascular region.

Mount one of the scales which enwrap a young
leaf. Examine with a low power, and note

22. The shape and arrangement of the cells.

23. The fringe at the free end of the scale. Notice of

what each hair of the fringe consists.

Cut a transverse section of these scales by cutting a
transverse section at the base of a pair of young leaves.
The sections of the scales will float off when the leaf section
is placed in water. Note

24. The number of cell rows m thickness ; the shape of

the cells and thickness of the walls of some of them.

25. A trace of a fibro-vascular bundle in the center of some

of the thicker scales.

C. THE FLOWERS.

1. The stamens. Tease out a portion of the wall of an
empty pollen sac. Examine with a high power, and
note

a. The shape of the cells.

b. The beaded appearance of the walls.

1 5 8 SCO TCH PINE.

c. Draw a few cells.

Place an entire male flower, from whose pollen sacs the
pollen has all escaped, between pieces of pith and cut trans-
verse sections of the cluster. Chance sections of the walls
of the pollen sac will thus be obtained. Examine with
a high power, and note

d. The number of cells in thickness.

<?. The reticulated thickening of the lateral walls,

which gives rise to the beaded appearance seen in

the surface view. Draw.

Break open two or three pollen sacs and mount the
pollen. Examine with a high power, and note in each
grain

The three lobes into which it seems to be divided :
a central one, the essential part of the grain ;
attached to this two vesicular protrusions or wings
with wrinkled surfaces.

g. In the central lobe make out

i. The double wall of the cell ; the outer part,

the extine, rather thick and having its
slightly roughened external portion expanded
into the vesicular wings ; the inner, the intine,
very thick and transparent.

ii. The contents (treat with iodine) ; protoplasm,

abundant starch, and sometimes one or two
clear-looking drops of oil.

iii. The division into two cells : one very large,

containing the starch and oil ; the other very
small, at the end of the central lobe furthest

from the wings, best seen when the grain is

lying on its side.
Treat the iodine-stained pollen grains just examined with
75$ sulphuric acid. Press gently on the cover glass with

PL\ US S YL VES TRIS. 1 5 9

the handle of a dissecting needle. Examine with a high
power, and note

//. The empty extine, distorted by the pressure, and

stained yellow.
#. The intine, blue, much swollen, and either empty

or still containing the protoplasm, starch and

oil. If empty the smaller cell can usually be well

seen.

j. The yellow protoplasm, dark blue starch grains and

clear oil drops, escaped from some of the pollen

grains.
k. Draw a pollen grain, showing all its parts.

2. The cone. Take a cluster of female flowers, bisect it
longitudinally, and from one of the halves cut longi-
tudinal radial sections. Treat with potash. Examine
with a low power, and selecting a section which has
passed through an ovule, note

a. The central axis bearing the bracts, each subtend-
ing a carpellary scale, to whose upper surface the
ovule is attached.

b. The body of the ovule, nucellus, surrounded by

c. The integument, which is prolonged beyond it.

d. The continuity of the nucellus and integument

with the carpellary scale.

e. The orifice in the integument at its proximal end,

the micropyle.

Draw, showing the above points.
Examine with a high power, and notice
g. That the cells of the nucellus, integument and

scale are all alike parenchymatous and filled with
protoplasm.
Dissect out a carpellary scale from the central part of a
year-old cone and cut a series of longitudinal sections,

1 6 o SCO TCH PINE.

including about the middle third of the ovule. Mount all
the sections, and treat with potash. Examine with a low
power, and note

h. The parts of the ovule : integument, nucellus and

micropyle.

/*. The parts of the scale : the scale proper and the

wing of the seed. Notice that the tissues of the
scale are continuous with those of the wing and
ovule ; a faint trace of the coming lines of separa-
tion may however be detected.

/. The differentiation of the tissues of the scale into

two kinds : the one of densely packed small cells
forming an outer layer with deeper seated fibers ;
the other of looser larger cells, forming the inter-
mediate portion.

k. The differentiation of the integument of the ovule

into two layers, the outer of densely packed small
cells, the inner of looser larger cells.

/. The discoloration of the apex of the nucellus.

m. The presence of a large cavity in the nucellus, the -

embryo-sac, filled with a delicate transparent tissue,

endosperm.

Examine with a high power, and note

n. That the body of the nucellus is almost entirely

displaced by endosperm cells.
o. The wall of the embryo-sac ; wavy and usually

broken away from the remaining cells of the
nucellus in cutting the section.
/. The endosperm cells j observe

i. The delicacy of the walls.
ii. The contents j thready protoplasm and a very

large round nucleus with a nucleolus. •

iii. Draw a few endosperm cells.

PIX US S YL VE S TRIS. 1 6 1

q. Near the outer end " of the embryo-sac, one or two

much larger cells, the archegonia or corpuscula."
Observe the distinct row of endosperm cells,
smaller than the others, which surrounds the arche-
gonia.

r. Occasionally one or two pollen grains having

shed the extine, may be found in the micropyle,
and still more rarely, some may be found which
have begun to emit their tubes.

s. Make a diagram of the ovule and all its parts, -

together with the wing and carpellary scale.

ANNOTATIONS.

The Scotch pine raises a strong tall stem above the
ground for the purpose of better exposing its leaves
and fruits to the air and sunlight. This habit is cor-
related with the excessive development of the fibro-
vascular system, which includes all the tissues of the
mature stem, with the exception of a trifling amount
at its center and circumference.

Not only is there provision for continued growth in
length by the formation of terminal buds, as in Adi-
antum, but there is also provision for growth in diameter.
A part of the tissue, from which the fibro-vascular
bundles are formed, lying between the xylem and
phloem, retains the power of division and by annual
increase in the number of cells, chiefly in a radial
direction, the thickness of the bundle is increased. The
difference in the size and shape of the cells added to
the xylem in the spring and autumn gives rise to the

12 /. <?., the end nearest the micropyle.

13 Frequently not well developed at this time.

1 6 2 SCO TCH PINE.

so-called annual or growth-rings which can be seen in
the wood.

The scales which cover the stem, though called by
the same name as the brown chaffy appendages to the
stem of the fern, are not trichomes like them, but
leaves. In addition to these scale leaves, which per-
form only slightly the function of true leaves, there
are the needle leaves, upon which the foliage work
chiefly depends. The delicate scales which enwrap
the bases of the needle leaves are not trichomes, but
leaves, as the rudimentary fibro-vascular bundle in
them shows.

The different mode of arrangement of the scale
leaves (and consequently of the dwarf branches) upon
the terminal and lateral shoots is worthy of notice.

Concerning the homology of the parts of the male
and female flowers, more especially the latter, there
has been and still is much controversy. It is gener-
ally admitted that each cluster of stamens constitutes a
single male flower. The scales which bear the pollen
sacs on their under sides are homologous with leaves,
as is shown by their position and anatomical characters
and occasionally in teratological changes.14 Moreover,
the flower is subtended by a bract, and the floral axis
bears several (usually three) bractlets below the
stamens.15

As first announced by Robert Brown 10 the ovule in
the pines and their allies is naked, *. e. it is not sur-
rounded, as in the vast majority of flowering plants,

14 Eichler, Bluthendiagramme, p. 59.

15 Cf. Strasburger, Das botanische Practicum, p. 469.

Appendix to Botany, Capt. King's Voyage, iv, p 103.

PIN US S YL VESTRIS. 1 6 3

by an ovary ; whence the entire group of plants having
this character are called gymnosperms. Latterly, there
has been much controversy as to the nature of the
carpellary scale and whether the ovule is really or
only apparently naked. The latter question involves
the determination of the nature of the integument
of the ovule. It is held on the one hand that the
ovule consists of nothing but a nucellus, and that
the coat surrounding this nucellus is the homologue
of the wall of the ovary. On the other hand it is
contended that this structure is the true integu-
ment of the ovule and that the scale which bears
the ovule is an open carpel or pair of carpels.17 In
the laboratory directions we have adopted the latter
view, calling the organ which bears the ovules a carpel-
lary scale. This carpellary scale is theoretically " com-
posed of two leaves of an arrested and transformed
branch from the axil of the bract, which are in the
normal manner transverse to the subtending bract,

each bearing an ovule on its dorsal [as to
position, upper] face; the two are coalescent into one
by the union of their posterior edges, and the scale
thus formed is thus developed with dorsal face pre-
sented to the axis of the cone, the ventral to the bract.
It is therefore a compound open carpel composed of
two carpophylls. This character of being fructiferous
on the back or lower side of the leaf occurs in no other
phaenogamous plants.

* * #

" 18

11 References to extensive literature of this discussion may be found in
Gray, Struct. Bot.f p. 272. For a general statement of views and
summing up of argument see Eichler, Sind die Coniferen gymnosperm
oder nicht? Flora, 1873, P- 241. Consult also Sachs, Text-book, 2nd
Eng. ed., footnote, p. 507. From references in these places the whole
subject may be traced.

18 Gray, Struct. Bot., p. 273, footnote.

1 64 SCOTCH PINE.

As soon as the male flowers begin to scatter their
pollen to the wind, the axis of the young cones elon-
gates, separating the carpellary scales sufficiently
to allow the pollen to be blown in between them,
and to slide down, guided by the keel, to the pro-
longations of the integument. These prolongations
subsequently roll inward, thus carrying any grains
which may have become attached to them to the apex
of the nucellus. After this process of pollination is
accomplished the bracts cease to develop and like-
wise the now useless keel.19

The minute anatomy of the Scotch pine presents
many points of considerable interest.

True tracheary tissue is formed only at the peri-
phery of the pith, where a cluster of spiral, reticulated
and pitted vessels occurs at the apex of each woody
wedge.

The tissue of the wood is almost exclusively made
up of tracheides, on whose radial walls are bordered
pits. As these walls, originally thin and plain, increase
in thickness irregularly, a part of the thickening on
each side of the primary wall grows away from it
to form the arched " border " of the small aperture
which remains. For some time the primary wall
remains as a membrane separating the two cells ;
when finally this is destroyed there is free communica-
tion between the contiguous cells. 20

The thin delicate walls of the cambium allow great
activity of the contained protoplasm, which results

19 Strasburger, op. cit., p. 476.

20 Cf. Strasburger, Bail und Wachsthum der Zellhaute, p. 43, taf.
iii. For figures cf. Sachs, Text-book, p. 25.

PIN US SYLVES THIS. 1 6 5

in the formation by division of many new cells. The
older cells on the axial side become gradually trans-
formed into the tracheides and those on the peripheral
side into the elements of the phloem.

Replacing the tracheides of the xylem are the sieve
cells of the phloem. The radial walls of the larger cells
have on them clusters of small perforations which are
known as sieve plates or disks. These sieve plates are
homologous with the bordered pits on the tracheides of
the xylem." At a little distance from the cambium
they become covered with a homogeneous substance,
the so-called callus plate, which completely interferes

■

with the function of the sieve cells. Though this callus
plate is subsequently dissolved, the sieve cells never
regain their activity, the protoplasm having by this
time disappeared from them. aa

The cells with brown and crystalline contents are
the true phloem parenchyma. A single row of them
is formed each season, so that the age of the stem may
be determined by these, M as also by the growth rings
of the xylem.

The general arrangement of the tissues of the bun-
dles is in contrast to that in the fern. The xylem and
phloem here lie side by side, whence the bundle is
known as collateral. a4

The rigidity of the leaves of the pine is due to the
thickening of the cells of the epidermis, together with
the development of the layer or layers of hypodermal
fibers.

Strashurger, Das botanische Practicum, p. 143.

n Strasburger, op. cit., p. 147.

23 Strasburger, op. cit., p. 146.

24 Russow, Vergl. Untersuch., fide DeBary, Comp. Anat., p. 319.

1 6 6 SCO TCH PINE.

Although the guard cells of the stomata appear at
first sight to be deeper seated than the epidermis,
observation teaches that they have been pushed down
by the crowding over them of the adjacent epidermal
cells, and here, as always, belong to the epidermis.
This is confirmed by examining younger stomata.

The partial partitions by which the mesophyll cells
are distinguished are explained by Sachs" as intru-
sive foldings due to local growth of the wall at the
point where the fold occurs. Corry 26 however asserts
that there is no real, but only apparent ingrowth,
which is caused in this way : when the cells are still
small their nuclei are attached to the protoplasm lining
the wall by delicate protoplasmic strands one or more
of which at a later period become converted into cel-
lulose thus attaching the nuclei firmly to the wall.
When the cell enlarges these points are firmly held
near the nucleus. Since some of the strands soon
break, many of the infoldings are shallow while others
holding, cause deep infolding. 27 The purpose of these
infoldings is considered by Haberlandt to be to
secure a greater surface on which to display the
chlorophyll bodies. Corry says of them : " They per-
form at all events a very obvious and noteworthy
function in forming the intercellular spaces beneath
the stomata in Pinus, and in producing air channels

25
26

Text-book, 2nd Eng. ed., p. 74.

On some points in the structure and development of the leaves of
Pinus sylvestris. — Proc. Camb. Phil. Soc, iv (1883), p. 344 et seq.

27 Similar infoldings in leaves of Elymus Canadensis and other grasses
are described by Kareltschikoff (Bull. Imp. Soc. Nat. Moscow, xli
[1868], p. 180) and in Caltha palustris, Anemone nemorosa and a
number of other plants by Haberlandt (Oester. Bot. Zeit., xxx [1880],

p. 305).

PIN US SYLVES TRIS. 1 6 7

between the cells forming the several rows of palisade

»» 28

tissue.

The four bundles of each pair of leaves have the
normal orientation, the xylem portions all facing a
common center and the phloem the periphery. The
imbedding of the bundles in a mass of colorless tissue
surrounded by a sheath is common among the pines
and their allies.

In this central tissue many of the cells are tracheides
(see fig. 7), as pointed out in the laboratory part ; they
are arranged in a special manner and are characteristic
of Coniferce™ These tracheides during the activity
of the leaf contain water, ,0 and hence have been, called
transfusion tissue by H. v. Mohl" and others.

The existence of occasional poorly developed resin
passages in the xylem of the leaf bundles is to be noted,
as it has been denied by Corry" and Van Tieghem.
(See fig. 7 r).

In comparing the reproduction of the pine with
that of the fern and earlier forms we find advances of
much interest. In the fern, as in the moss and liver-
wort, the spore grows into a structure, which bears
the reproductive organs. In the moss and liver-
wort this sexual or thalloid stage comprises by far the
larger part of the life cycle, while the asexual stage
(the so-called fruit) is small and quite unable to lead
an independent existence. In the fern the thalloid

Op. cit., p. 355.

'9 Cf. DeBary, Comp. Anat., p. 378 et seq.

30 Strasburger, op. cit., p 234.

31 Bot. Zeitung, 1871, No. 1, 2.

32 Op. cit., p. 359.

33 Ann. Sci. Nat., Ser. V, xvi (1872), p. 189.

1 6 8 SCO TCH PINE.

stage is much reduced, although still green and able
to maintain itself for a limited time, while the asexual
stage is the conspicuous part of the plant, in fact the
only part usually noticed, except by students and fern
propagators.

From the fern to the pine is too great a step to be
well understood without considering some intermediate
type. Some species of Selaginella would answer this
purpose admirably, and it is to be regretted that no
species is sufficiently common in this country, either
wild or cultivated, to permit the introduction of direc-
tions for its study in this manual. It must therefore
suffice.to mention one feature of Selaginella indispens-

able for a clear understanding of the subject in hand.

Selaginella, instead of having only one sort of spores,
as in the ferns and liverworts, has two, one small (micro-
spores), the other large (macrospores). When these
spores vegetate, the prothallium from the smaller one
bears the male organs (antheridia), and that from the
larger the female organs (archegonia). A very marked
feature is that the prothallia are greatly reduced, so
much so in fact that they never leave the spore or
become green, and the one from the smaller spore is
even reduced to a single small cell.84

To return to pine, we shall find that the reduction of
the sexual stage or prothallium is carried a step, and
quite a long step further than in Selaginella, while the
asexual stage is augmented in the same proportion.
The latter in fact is the pine tree — the whole plant one
would naturally say. It must be borne in mind that in

For further description see Bessey, Botany, p. 385 ; Sachs, Text-

•

book, p. 468.

P A V US SYLVES TRIS. 1 6 9

the fern the asexual plant produces spores, and that in
Selaginella, a more advanced type, it does also, but of
two sorts. Does the pine likewise produce spores ?
Certainly, although we have so long called them pollen,
that we are inclined to forget their true relation,
which would be better indicated by the term pollen
spores, used by DeBary." These pollen spores cor-
respond to the microspores of Selaginella, and like
them have the prothallium reduced to one or a few
cells, but unlike them do not produce antherozoids.
This, however, is a matter of adaptation. Wherever
there is water to transport the fertilizing element
from the male to the female organs, it is usually
an active body (antherozoid), as in Adiantum, Atri-
chum and Marchantia, with an exception in Spirogyra,
while if it must be transported through the air or the inte-
rior of plant tissues a tube leads from the antheridium
to the archegonium as in Microsphaera and Cystopus.
Pine like other flowering plants has the spores carried
bodily through the air in order to bring them into
proximity to the female element, then a tube (pollen
tube) develops, which connects the male and female
organs. Turning now to the female part, which cor-
responds to the macrospore of Selaginella, it (now called
the embryo-sac) is found so greatly reduced that it
never leaves the place in the mother plant where
formed. The prothallium is represented by the pri-
mary endosperm. The archegonia themselves are
much simplified as might be expected. They arise
from superficial cells of the endosperm (prothallium).

Morph. u. Biolog. d. Pilze, Mycet. u. Bacterien, 1884, p. 140.

1 7 o SCO TCH PINE

Within each is a large nucleated germ cell or oosphere,
the part to be fertilized.

The process of fertilization is as follows : The
pollen grains having been lodged in the micropyle
upon the apex of the nucellus, the extine is burst and
slipped off by the swelling of the intine and its con-
tents. By a local growth the intine extends into a
tube into which the contents of the larger cell pass by
a streaming movement, the smaller cell remaining
inert. This pollen tube pushes its way slowly between
the cells of the nucellus until it reaches the germ cell
in the embryo-sac. Shortly afterward a nucleus almost
as large as that of the germ cell appears below the end
of the pollen tube. It is to be supposed that it has
passed through the wall of the tube, and it is to be
regarded as homologous with the body of an an-
therozoid. The two nuclei fuse into one, which passes
to the end of the germ cell opposite the neck where it
gives rise to several four-celled layers, one above
another, the lower four of which form the beginning
of the embryo.36 This process of fertilization requires
in Pinus sylvestris a little more than a year between
the beginning of the growth of the pollen tube and
the consummation.

The fertilized germ cell grows at once into the young
plantlet (embryo), as in the fern, but at this stage,
unlike the fern, it stops for awhile, and in the passive,
well protected condition of a seed may pass a long
period before it resumes its growth. This, again, is a
special adaptation. All the plants heretofore con-
sidered are fully equipped for the dispersion of each

36 Cf. Strasburger, op. cit. , p. 481 et seq.

PIN US S YL VES TRIS. 1 7 1

succeeding generation through their sexual or asexual
spores, or the division of the vegetative members. In
the pine the young plantlet is developed before leaving
the parent, and were it to continue to grow would
either live wholly upon the parent, or be brought into
such close competition with it, that the species would
speedily become extinct. Therefore, to provide for
the proper dispersion of the offspring, the young
plantlet is suitably protected, and provided with food
for its first growth when again resuming its develop-
ment, separated from the parent, and wafted away by
the wind in the utmost security.

This is one of the most characteristic features of the
higher plants, from which they might better have been
named seed-bearing plants, than flowering plants.

It is also worthy of notice that the primary endo-
sperm which is formed during the first year of the
fruit, and on which the archegonia arise, is subsequently
destroyed by the deliquescence of the cell-walls ; and
from the protoplasm thus set free there is produced
in the spring of the second year what may be called
secondary endosperm which, with the growing embryo,
fills up the embryo-sac and displaces the most of the
tissue of the nucellus.87

Cf. Sachs, Text-book, 2nd Eng. ed. p. 521.

FIELD OATS

A vena sativa L.

PRELIMINARY.

THE cultivated grass known as oats is too familiar to
need description. Specimens should be collected at
the time when some flowers of the panicle are
expanded and others are yet in the bud. This plant
begins to bloom shortly after the panicle is liberated
from the sheath. The time of blossoming is so little
marked by external changes that there is great danger
that specimens will be collected too late. Care should
be taken in lifting the plants from the ground not to
detach the empty grain from which it grew, which will
almost certainly be done if the plants are pulled up.
They should be dug and the dirt shaken gently from
the roots, which may be further cleaned by washing.

The requisites for the complete study of the plant
are entire plants, preserved in alcohol ; a handful of
threshed oats ; alcohol ; magenta ; potassic hydrate ;
and iodine.

LABORATORY WORK.

GROSS ANATOMY.

A. GENERAL CHARACTERS. Note the four parts
of the plant :

A VENA SATIVA. 1 73

i. The roots.

2. The upright main axis, the stem, with numerous
branches near the top.

3. The lateral appendages of the stem, the leaves.

4. The surface appendages on the roots and leaves, the
trichomes, in both instances extremely minute.

B. THE ROOTS. In a plant which has the emptied
grain from which it grew still attached, note

1. The small group of roots arising from one end of the
grain, the strongest of which is the primary root.

2. The stem emerging from the other end, the first inter-
node of the stem.

3. At a certain point,1 the second node of the stem, a whorl

of secondary roots.

4. At one or two succeeding nodes, a like whorl of sec-
ondary roots.

5. Make a diagram, showing the position of the roots
and their relation to the lower part of the stem.

Cut a transverse section of one of the large secondary
roots. Examine by transmitted light. Note

6. The round central spot of firmer tissue, the fid ro -vas-
cular bundle. The openings in it are the larger vessels.

7. The loose, pith-like cortical portion.

8. The root-hairs, attached to the edge.

9. Draw.

1 Known to agriculturists as the "tillering point." The length of
this first internode depends to a considerable extent on the depth of plant-
ing the seed.

174 FIELD OATS.

Strip off the cortical portion of one of the large secondary
roots. Notice

10. The slender, strong nbro-vascular axis which remains.

Examine some plants three or four days old, which have
been grown on the surface of wet blotting paper. Note

ii. The position of roots and stem with respect to the

grain.

12. The abundant root-hairs. Notice their relative length

on different parts of the root, and where absent.

13. The opaque tip of the root covered by the conical root-
cap.

C. THE STEM. Notice that it is completely encased by
the sheathing bases of the leaves. Uncover a portion of
the stem by removing one of the leaves and its sheath, and
note

1. Its shape y and polished surface.

2. Its nodes and intemodes. Bisect the stem longitudinally
through a node and a portion of an internode. Note

a. The solid node forming a partition between the

cavities of the internodes.

b. Draw.

Look through the split stem at a bright light, and note

3. The numerous threads, traversing the stem lengthwise,

the fibro-vascidar bundles.

Cut a transverse section and examine by transmitted light,
and note

4. A very firm, more opaque external layer, the cortical
layer. Notice its variable thickness.

5. In the cortical layer, pairs of darker spots. These are

clusters of chlorophyll-bearing cells.

A VENA SATIVA. 175

6. The remainder of the section made up of large rounded

cells, parenchyma, scattered through which are

7. Masses of firmer tissue, the fibro-vascular bundles, each
having three or four openings, the vessels.

8. Draw the section.

Cut a number of longitudinal sections ; in them make
out

9. The denser cortical portion.

10. The more transparent parenchyma.

11. The fibro-vascular bundles.

12. In a section not passing through a fibro-vascular bun-
dle, the strip of darker chlorophyll-bearing tissue
under a very narrow cortical layer.

13. Draw a section, showing as much as possible of the

structure.

D. THE LEAF. Note

1. Its sheathing base. Observe the extent of stem cov-
ered by each sheath.

2. The split in the sheath ; its position and extent.

3. On the upper surface at the point where the sheath

ceases, a thin membranous outgrowth, the ligule.
Notice its shape and apex. Draw.

4. The place of attachment of the leaves.

5. The remainder of the leaf, the blade. Note

a. Its shape.

b. The numerous veins ; their direction and relation

to the ridges.

c. The green tissue (bleached by alcohol) between

the veins, the mesophyll.

176 FIELD OATS.

Cut a transverse section of the blade, and note

6. The variable thickness of the leaf.

7. The sections of the fibro-vascular bundles.

8. On the upper edge, large cells between the ridges, the
hygroscopic cells, which cause the leaf to roll when dry.

E. THE FLOWERS.

1. The arrangement of the flowers, anthotaxy. Note

a. The central stem of the flower cluster, the main

axis of inflorescence.

b. Its lateral branches, secondary axes. Notice their

relative lengths.

c. That some of the secondary axes are branched,

others not, thus constituting a panicle,

d. Make a diagram of the mode of branching.

e. That each ultimate branch bears not a single

flower, but a cluster of three (sometimes two)
flowers, a spikelet, at the thickened extiemity.
The entire inflorescence is thus compound, a

panicle of spikelets.

Detach a spikelet, and note

Two bracts at the base of the spikelet, completely
inclosing the flowers, the empty glumes. Notice the
position of these glumes with respect to each
other and their points of attachment. Detach
them, and note

i. Their shape.

ii. The parallel veins, nerves j the number in

each glume, the termination above, the deli-
cate cross (anastomosing) veinlets.
iii. Draw.

AVE A' A SATIVA. 177

g. The three flowers inclosed by the empty glumes ;

their relative size2 and position on
//. The flattened axis on which they are borne, the

rhachis of the spikelet.

/*. The tufts of minute hairs at the base of the lowest

flower.

/. Draw a spikelet, showing the empty glumes and

flowers separated from one another.

2. 'Wit, structure of the flowers. Detach the lowest flower
in the spikelet. Note

a. The bract, flowering glume,' which almost incloses

the flower. It sometimes bears a long bristle-like
appendage or awn on its outer surface ; note
position when present. Detach this bract entire,
and note the size, shape, surface, texture, notched
apex and number of nerves. Draw.

From another flower cautiously detach the flowering
glume by cutting and tearing it away piece by piece, leav-
ing only a bit of its base, being careful not to injure

b. The flower proper. Observe

i. A large bract-like body, the palet,4 its infolded

margins, shape, nerves, and the presence and
position of the trichomes on its outer surface ;
contrast it with the flowering glume. Draw ;
also make a diagram of a transverse section
at its middle.

ii. Two small bract-like bodies, the lodicules,

situated between the edges of the palet. Ob-
serve their shape and texture. Draw.

a The third is rudimentary
flower.

8 Called the lower palet in most systematic works.
4 Called the upper palet in most systematic works,

178 FIELD OATS.

iii. The three similar stamens. Examine one care-
fully, and note three parts :
a. The slender thread, filament, carrying at

its apex

A two-lobed body, the anther ; note

the deep groove lengthwise of each lobe,
and the point of attachment of the fila-
ment.

y. Tear open an anther, or examine one

which has burst, and notice the cavities
containing pollen ; the color and powderi-
ness of the grains.

d. Draw a stamen,
iv. The hairy body in the midst of the stamens,

the pistil. Note its three parts:

a. The large, top-shaped part at the base,

clothed with white hairs, the ovary.
The two thread-like bodies arising from
the top of the ovary, the styles.

y. The numerous branches6 of the styles

arranged like the barbs of a feather, the

stigmas.

6. Draw a pistil.
Cut a pistil in two longitudinally between the styles,

and notice

s. The thick but delicate wall of the ovary.

Z. The ovule of denser tissue closely adher-
ing to it, and mostly occupied by

rj. A cavity, filled when growing with the

transparent endosperm, which cannot now

be easily detected. In this cavity notice

5 If hidden by many adherent pollen grains, brush them off with a camel's-

hair brush.

A VENA SATIVA. 1 79

©. The early stage of the young plantlet of

the seed, the embryo.
1. Illustrate with diagram.
Compare with this flower the second and third flowers of

the spikelet. Note, in the latter, the absence of the inner
organs, leaving only the flowering glume, palet, and some-
times the stamens.

F. THE FRUIT. Study ripe oats which have been
threshed or shelled out in the hand. Strip off the chaff
(flowering glume and palet) which incloses the fruit. Note

1. The white hairs which cover it, especially at the upper
end.

2. The longitudinal groove ; its position as to the palet.

3. The scar at the base of the grain opposite the groove,
marking the position of the plantlet within.

Cut across the middle of a grain, and note

4. The depth of the groove, and the uniform floury
contents ; test with iodine.

5. That the wall of the ovary and the coats of the ovule
have become so closely united and thin as to be indis-
tinguishab'e, thus ccnstituting the fruit a caryopsis or

grain.

6. Draw the section.

From a soaked grain carefully remove the " skin " (the
wall of the ovary together with the seed coats) on the side
opposite the groove, from the lower end to the middle.
There will then be seen a face view of

7. The embryo. Note

a. The large elongated-triangular body forming the

1 So PI ELD OA TS.

upper part of the embryo, the cotyledon or scutellum.

b. The pointed lower extremity, the root sheath.

c. Near (below) the center of this face of the embryo,

a minute bud, the plumule.

d. Just below the base of the plumule, a very short

stem, the caulicle

e. Draw the embryo as it lies exposed.
Bisect a grain longitudinally through the groove. Mount
also a thin section from the cut surface. Note

The scutellum, with its back against the starchy
part of the seed, its face just under the "skin"
at the upper part of the embryo.
g. The plumule, on the face of the scutellum, at the

upper end of

//. The caulicle; easily recognized as the whitish

part where the scutellum and plumule merge.
At its lower extremity is
/. The root, a small rounded point, over which is
/. The root-sheath, which forms the lower extremity

of the embryo.
k. Draw the section.
Take a series of transverse sections from the bottom of
the grain upward. Examine the successive cut surfaces and,
comparing with the longitudinal secti@n, determine the
various parts seen, root-sheath, root, caulicle, plumule,
scutellum. Draw those which show the section of root and
root-sheath, and the section of plumule and scutellum.

MINUTE ANATOMY.

A. THE ROOTS. Cut a transverse section of one of the
lateral roots at a little distance from the stem. Examine
with a low power, and note the two regions :

6 111 defined and difficult to see.

A VENA SATIVA. 181

i. The cortical, thin-walled cells.

2. The fibro-vascular, thick-walled cells.
Examine with a high power, and note

3. The thin-walled epidermis. Observe its irregularity,
and the mode of attachment of the root-hairs. Draw.

4. The cortical parenchyma^ with sclerenchyma either
intermixed, or in older roots forming an outside layer.
I ) raw.

5. The bundle sheath ; the relative thickness of outer and
inner walls ; the pits. Draw.

6. The fibro-vascular bundle. Study

a. The smaller thick-walled cells constituting most

of the bundle.

b. The vascular tissue ; four to six (sometimes more)

large pitted vessels symmetrically disposed. Between
each of these and the bundle sheath (also some-
times near the center) a dozen (more or less) of
smaller pitted vessels.

c. Numerous channel-pits in all the thick-walled

cells.

d. Draw a portion of the bundle.

Cut a longitudinal section of the same root. Examine
with a high power, and note

7. The epidermal cells. Observe the bases of root-hairs,
and their relations to the epidermal cells. Draw.

8. Elongated cortical parenchyma and occasionally
sclerenchyma. Notice the pits. Draw.

9. The bundle, sheath ; cells elongated, rather difficult to
distinguish. Draw.

10. The fibro-vascular bundle. Study

1 8 2 FIELD OA TS.

a. The pitted fibrous cells, tracheides, which constitute

most of the bundle.

b. The one or two pitted vessels.

c. Draw, showing both vessels and tracheides.
Mount about one centimeter of the tip of a root from

plants that have been grown upon blotting paper. Exam-
ine with a low power, and note

ii. The root-hairs. Observe their relative length.

12. The root-cap ; the outer cells sloughing off. Draw.
Study the root-hairs with a high power. Notice

13. The shape, mode of attachment and contents. Draw.

Cut a median longitudinal section of the tip of a root,
including the root-cap.7 Treat with potash, examine with
a high power, and note

14. The blunt, or even notched tip of the root proper.

15. The sharp conical root-cap. Note the shape of the

cells near the root-tip, and the changed shape near the
periphery.

16. The growing point, a cluster of small cells, just back of

the root-cap, in the middle of the root-tip.

17. A short distance behind the tip of the root, the slight

differentiation of the tissues into three regions :

a. A central one, the plerome.

b. An outer one, consisting of a single row of cells,

the dermatogen.

c. Between the plerome and dermatogen, the periblem.

d. Trace these three regions down to the growing

point, and notice their relations there.

7 This is very difficult to do if fresh roots are used, but easier by using
roots that have been kept for a few hours in alcohol. The student should
cut a series of sections through the whole root. The median one can then
be selected.

A VENA SATIVA. 183

e. Trace them backward ; notice that the plerome

becomes the fibro-vascular bundle ; the periblem,
the cortical parenchyma ; the dermatogen, the

epidermis.
Cut a transverse section of the oldest part of a root which
lias grown on blotting paper. Examine with a high power.
Compare with the section of the large lateral roots, already
studied. Notice

18. The origin of the root-hairs.

1 9. The differences in the fibro-vascular bundle, particularly

the presence of a large axial vessel.

B. T H K STEM. Cut a transverse section from one of the
younger parts of the stem, e. g.y between the flower cluster
and the first leaf. Examine with a low power, and note

1. An outer cortical part, of varying thickness, composed
of small dense-looking cells, the epidermis and hypo-

lerma.

2. In the cortex lighter spots, in pairs, at almost regular

intervals, chlorophyll-bearing parenchyma.

3. An inner part, consisting of large empty parenchyma
cells, the fundamental parenchyma, with fibro-vascular
bundles at regular intervals.

Examine with a high power. Study

4. The epidermis. Note the thick walls, showing two
layers, and the cuticle. Draw.

a. Observe in some sections a pair of smaller, peculiar

cells in the epidermis over an intercellular space
in the chlorophyll-bearing parenchyma, the guard
cells of a stoma. The two adjacent epidermal cells
are also modified somewhat. Draw.

5. The hypoderma. Note the thick walls of the cells

184 FIELD OATS.

which increase in size toward the parenchyma, but do
not merge into it. Draw.

6. The chlorophyll-bearing parenchyma. Note

a. The shape, size and arrangement of the cells.

b. The thin walls.

c. The contents ; protoplasm and chlorophyll bodies

which are green, if fresh stems are used. Notice
the position of the chlorophyll bodies.8

d. Draw a few cells.

7. The fundamental parenchyma. Note the size and shape
of the cells, and the triangular intercellular spaces.
Draw a few cells.

8. The fibro-vascular bundles. Notice the two series of
bundles : the larger ones nearer the central cavity of
the stem ; the smaller between the paired groups of
chlorophyll-bearing parenchyma. In the larger ob-
serve

a. The external sheath, an irregular layer of cells,

with slightly thickened walls,9 surrounding the
bundle, and thicker on its peripheral side. Exam-
ine it in a section from an older part of the stem ;
note the thickness of the walls.

b. The tracheary tissue ; on the right and left of the

bundle two large pitted vessels ; toward the axial
side one or two annular vessels ; between the
large pitted vessels a transverse band of smaller

pitted vessels.

c. Between the annular vessels and the external

8 They may be made plainer by staining with magenta.

9 If it can not be discerned, stain slightly with magenta ; these cells
take a deeper red than the rest.

10 Stained a deeper red in the magenta-treated section.

A VENA SATIVA. 185

sheath sometimes an intercellular cavity formed
by breaking in growth.

d. Toward the peripheral side of the bundle a group

of thin-walled conducting cells.11

e. Draw the bundle.

Compare the structure of the smaller bundles with
the foregoing, noting differences.
Cut a number of longitudinal sections of the stem, and
examine with a high power. Study

9. The epidermis. Note

a. The thickened outer wall ; elongated shape; chan-
nel pits.

b. The alternately long and short cells in some

sections.

c. Draw.

Some of the sections will be likely to pass through a

stoma. Examine

d. The guard cells ; note the enlarged ends and nar-
row body. Draw.

10. The hypoderma j note the extreme elongation and

tapering ends of the cells. Draw.

11. The chlorophyll-bearing cells ; note their shape, arrange-
ment and contents. Draw.

1 2. The fundamental parenchyma j note the size and

shape of the cells, and the thin places in the walls.
Draw a few cells.

13. The jibro-vascular bundles ; note in the various sec-
tions la

a. The slightly thickened, sparsely pitted, elongated

11 Unstained with magenta.

18 No one section can be found to show all points.

1 86 FIELD OA TS.

cells of the external sheath having slightly oblique

end walls.

b. The delicate walls and elongation of the conduct-
ing cells.

c. The pitted vessels, large and small.

d. The annular vessels. Notice the various positions

of the rings. Study their cut ends where the
razor has passed along a vessel.

e. Draw a few cells of each tissue.

Cut a thin slice from the surface of a stem, examine
with a high power, and note

14. The epidermis.

a. The cells above the hypoderma ; shape and ar-
rangement.

b. The cells above the chlorophyll tissue, including

the stoma ; shape and arrangement.

c. The numerous pits in the surface wall, and in the

side walls beneath.

d. Draw.

C. THE LEAF. Cut a transverse section, and examine
with a high power. Study

1. The epidermis. Notice

a. Its cuticularized outer wall with minutely uneven

free surface.

b. The guard cells. Note

i. The different appearance of these cells,

according as the section has passed through

the bodies or ends,
ii. The small size and thick walls of the body,

the larger size and thinner walls of the ends.

c. The modified epidermal cells adjoining the guard

cells.

AVEATA SATIVA. 1 87

d. Draw various sections of stomata, with adjoining

cells of the epidermis.

e. The modified large epidermal cells in the depres-
sions on the upper surface, the hygroscopic cells.

Draw.

The modified epidermal cells at the summit of each

ridge ; sometimes teeth may be seen. Draw.

2. The hypoderma. Note its position and the character
of the cells.

3. The mesop/iyll, all the chlorophyll-bearing part of the
leaf. Note

a. The slight elongation of those cells next the epi-
dermis, forming palisade parenchyma.

b. The large intercellular space under each stoma, and

the numerous smaller ones in other places.

c. The abundant chlorophyll bodies.

4. The fundamental tissue ; often reduced to only one
row of large empty cells surrounding the bundles.

5. The fibro-vascular bundles ; compare those forming the
midrib and main veins of the leaf with those studied in
the stem. Compare with these the bundles of the
smaller veins, noting what tissues are absent from
them.

6. Draw a portion of the section, including a large fibro-
vascular bundle, and some cells of the mesophyll and
fundamental tissue.

7. Make a diagram of the leaf section to show relative
position and size of the different parts.

Strip off two pieces of the epidermis. Mount one piece
with the outer surface uppermost, and the other with the
inner surface uppermost. Note

1 88 FIELD OATS.

8. The epidermal cells.

a. The shape of those lying above a vein, together

with the short strong trichomes, each bearing a
very sharp point, directed forward.

b. The shape of those lying among the stomata.

c. The sto?nata. Note

i. The regular arrangement in double or triple

rows,
ii. The pair of narrow epidermal cells, which

stand one on each side of the guard cells,
iii. The shape of the guard cells ; the thick walls

of the body and thin walls of the ends,
iv. Draw, showing the several sorts of epidermal

cells.

9. The shape and contents of the mesophyll cells, some of
which will almost invariably adhere to the epidermis
when stripped off. Draw.

10. Make a transverse section of the leaf sheath, and note

its intermediate character between that of the stem and
of the leaf blade already studied. Draw sufficient to
show the various tissues, and their arrangement.

D. THE FLOWER.

1. The glumes and palets. Make a transverse section
through the upper part of a spikelet and transfer it to
the slide without disarranging the parts. Note

a. The thin-walled cells forming the inner portion,

and the thick-walled cells forming the outer por-
tion of each part. Draw from two or more
regions.

b. The angles of the palets, bearing stiff trichomes.

Draw.

A VEX A SATIVA. 189

2. The anthers. Tear off bits of the wall of an empty
anther. Mount one outside up and the other inside up.
Focus on the surface of the first, and note

a. The epidermis ; its wrinkled walls ; the shape of

its cells. Draw.

Focus on the surface of the second, and note

b. The endotheciumy the layer of cells lining the

anther. Observe

i. The infolded thickenings of the side walls of

the cells,
ii. The shape of the cells,
iii. Draw.

Cut a transverse section through the lower part of a
spikelet which has not bloomed, and transverse sections of
the anthers will be obtained. Notice

c. The large inflated epidermal cells.

d. The very narrow endothecial cells, with the thick-
enings of the walls extending the full height, mak-
ing it difficult to distinguish their outline.

e. Draw a few of the two kinds of cells.
Under low power, notice

The two lobes of the anther, thecce.

g. The connective which joins them, containing a fibro-

vascular bundle.

//. The four cavities, appearing like two after dehis-
cence. Usually the manner of dehiscence can
be detected.

Using the same section, under high power, notice

3. The pollen.

a. The shape of the cells.

b. The small globular protuberance sometimes seen

when the spore lies properly.

190 FIELD 0A TS.

c. The optical section of the wall ; its continuity inter-
rupted at the protuberance.

d. The contents. Burst some spores by pressing

lightly on the cover-glass with a needle. Note
i. Here and there entirely empty bursted sacs,
the extine. Notice the minute roughening

of the surface ; the thin spot or opening,
through which in some cases when unburst the
intine protrudes.

ii. The contents of some spores surrounded by the

intine, escaped from the extine and become
much larger. In some cases the protuberance
may still be seen.

iii. The contents of other spores free in the water

of the slide, showing innumerable fine gran-
ules. Note their shape, and treat with iodine
to determine their nature.

e. Draw an uninjured spore, showing its structure.

4. The styles and stigmas. Cut off one of the styles near
its attachment. Mount and examine with a low
power. Note

a. The tapering style with

b. Numerous undivided branches, the stigmas,

roughened with innumerable points.

c. The grains adhering to the stigmas.
Examine with a high power. Observe

d. The thin-walled nucleated cells, forming the stig-
mas ; the proximal ends are overlapped by other
cells.

e. The adherent grains. Notice that some of the

spores have emitted through the perforation in

% the extine a slender tube which penetrates the

stigma. Notice that the granules of the pollen

A VENA SATIVA. 191

spore also enter this tube. Observe that some
spores have become empty.

Draw, showing structure of stigmas and the
entrance of a pollen tube.

5. The trichomes of the ovary. Cut off, mount, and
examine with a high power some of the trichomes which
clothe the apical portion of the ovary. Note shape and
contents. Draw.

E. THE FRUIT. Remove the chaff from a grain, and
cut a transveuse section near the middle, having previously
soaked it in warm (not hot) water for a few minutes."
Note

1. While mounting, the abundant whitish powder which
escapes into the water, clouding it more or less.

Examine with a high power and note

2. The outermost coat of the fruit, the ovary wall, some-
times splitting into two layers ; the cells can only be
made out with great difficulty.

3. The layer of large cells, containing granular proteid
matters, chiefly gluten. Note shape, and test contents
with iodine. Draw.

4. The large cells packed with granules of starch, made
blue by the iodine. The outline of these cells is best
seen when the starch has escaped from them.

5. The tip of the embryo will usually appear at one side of
the section.

Cut a median longitudinal section through the groove of
a soaked fruit. Treat with potash to clear up the embryo,
and examine with a low power. Note

13 An immersion of an hour or longer in cold water will answer the
same purpose.

*92 FIELD OATS.

6. The three parts of the fruit : the walls of the ovary
and gluten-containing cells ; the starchy part of the
grain ; the embryo.

Study the ejnbryo ; note

7. The long leaf, scutellum, next the starch.

8. The bud, plumule y near the base of the scutellum,
showing one or two leaves.

9. The root near the base of the embryo, with its root-cap,
and enveloped by

10. The root-sheath ; notice that it is continuous with

11. The short stem, caulicle, to which the scutellum is

attached, bearing the plumule at its upper and the root
at its lower end.

Examine with high power. Note

12. The tissues of the fruit, essentially as in the trans-
verse section.

13. The tissue of the embryo ; parenchyma with much

protoplasm.

ANNOTATIONS.

The division of the slender, slowly tapering stem of
Avena into ring-like nodes and elongated internodes
shows these features distinctly marked for the first
time. The disposition of the material in the form of
a hollow cylinder gives greater rigidity than would
the same amount of material in a solid stem.

■

At some of the lower nodes of the stem the endog-
enous formation u of roots can be well seen, as young

14 Cf. Prantl and Vines, Text-book, p. 22.

A VENA SATJVA. 193

roots can be frequently found just breaking through
the superficial tissues.

The leaves of oats are sharply distinguished into a
sheathing base and a spreading blade. The membra-
nous outgrowth, the ligule," which is found at their
junction, is common in leaves of this character.

The flower of oats, like that of the pine, is a meta-
morphosed shoot, in which the axis is the stem, and
the lateral organs which it bears, leaves. At the base
of each spikelet are to be found two glumes or bracts,
which thus subtend and more or less completely inclose
the whole cluster. At the base of each flower is a
single bract, the flowering glume, having the flower in
its axil. Concerning the homology of the palet and
lodicules much discussion has arisen. Payer ,6 asserts
that the palet is a double organ and that the two keels
on the palet are primitively distinct. Schacht IT
in the palet two parts of a trimerous whorl, of which
the anterior part is suppressed. Roper, Wigand,
Nageli and others conclude from comparative and
developmental researches that the palet is primitively
single and takes on its two-keeled condition subse-
quently.18 Hackel " believes " that the palea and the
pair of lodicules (when two only) are each single, more
or less bifid organs, and that they and the third lodi-
cule, when present, must be regarded as two or three

homology see Gray, Struct

211.

16 Organogenie de la fleur, p. 701.

11 Das Mikroskop, 2 Aufl., p. 170.

18 Cf. Eichler, BlUthendiagramme, p. 120.

Untersuchungen uber die Lodiculae der Graser, Engler's Bot. Jahr

bi'icher, i, p. 336.

194 FIELD OATS.

bracteoles inserted fore and aft on the floral axis below
the flower, and he has made out a good case in favor
of his view but perhaps not an unanswerable one." 20
Bentham " adds : " The search for homologies to the
palea and lodicules in the orders nearly allied to the
Graminece has met with but little success ; " and again,
" The palea and lodicules of Graminece may represent
perianth segments of an outer and inner series, though
I by no means pretend to assert it as a proved fact.
Again," " In all cases, the palea, whatever its origin,
is called upon in conjunction with the subtending
glume to perform more or less of the functions of the
deficient or absent perianth."

It is to be noticed that the male and female repro-
ductive organs occur in the same flower, which is

■

therefore hermaphrodite. The stamens of oats are
to be looked upon as metamorphosed leaves, as in the
pine ; it seems probable, though not definitely proved,
that the pollen sacs are homologous with those of the
pine. The immature pollen spore is two-celled, as in
most other angiosperms,83 and it is doubtful whether
there is any trace of a prothallium. This stage in the
life cycle of the plant, which is so marked in the moss
and liverwort, far less prominent in the fern, reduced,
if it can be considered present at all, to but a cell or
two in the pine, is in this plant probably entirely sup-
pressed.

Attention is called to the fact that the ovule is not

20 Bentham, Notes on Gramineae, Jour. Linn. Soc, xix, p. 23

21 L. c., p. 24.

22 L. c, p. 25.

23 Cf. Strasburger, Neue Untersuchungen, p. 5.

A VENA SATIVA. 195

naked as in pine, but that it is surrounded by an organ
peculiar to angiosperms, the ovary, which in this plant
adheres to the surface of the ovule. It is much better
developed in Trillium and Capsella, to which for its
study the student is referred. Since the ovule is thus
inclosed, stigmas have been developed as naked pollen-
catching surfaces, to which the pollen spores can
adhere, and through whose loose tissues they can eas-
ily send their tubes.

The adherence of the ovary wall to the ripened seed
gives rise to a fruit peculiar to grasses, the grain, which
is commonly mistaken for a simple seed.

The fibro-vascular system is well developed in oats,
and is of the typical monocotyledonous form. The
hypodermal fibers of both stem and leaves give addi-
tional strength to these organs. The bundles through-
out the stem are of the collateral type, as in the pine,
but with this difference ; whereas in the pine there
remains a cambium layer between the xylem and
phloem, here there is no cambium. The continued
growth of the bundle is therefore impossible, whence
it is known as a closed bundle. The axial bundle of the
root is, like that of the fern, a radial one. In the fern
root a single apical cell forms the growing point of
the root ; in oats the apical cell is replaced by a clus-
ter of cells. The remark respecting the root-epidermis
of Adiantum " is equally applicable here concerning the

older roots.

In the leaves the most novel structure is the groups

of hygroscopic, or as they were first named by Duval-

24 Cf. also Goodale, Physiological Botany, p. 108.

196 FIELD OATS.

Jouve," bulliform cells. They are found in all grasses
that roll and unroll their leaves. These cells when
they lose part of their moisture contract and roll up
the leaf, which again expands upon their regaining it.
This movement reduces the amount of surface available
for evaporation, and is a safeguard for the plant. It
will be remembered that the moss leaf accomplishes
the same result, but without a specialized apparatus.

*5 Etude anatomique de quelques Graminees, 1870, p. 320.

TRILLIUM.

Trillium recurvation Beck.

PRELIMINARY.

The Trillium designated, as well as T. sessile, is

found in the spring, generally in rich woods, and may
be readily recognized by the naked stems, from fifteen
to thirty centimeters (six inches to a foot) or more high,
bearing at the summit a circle of three broad netted-
veined leaves, at the center of which (the apex of the
stem) stands a single sessile dark-purple flower. The
stem rises from a deep-seated, somewhat toothed, very
thick rootstock, which bears the fibrous roots
along its under surface. In the other Trilliums, which
are at all common, the flowers are usually white
or pinkish, or purple in one case, and stalked. Any
species may be used for the laboratory work.

Although Trillium is now considered a member of
the lily family, the largest order of petaloideous mon-
ocotyledons, it is not a very characteristic member,
but has been selected for its general distribution, its
completeness and simplicity, and for its convenient
size.

The materials needed are fresh or alcoholic spec-

198 TRILLIUM.

imens of roots, rootstocks, stems, leaves, flowers
and fruit ; potassic hydrate ; magenta ; and iodine.

LABORATORY WORK.

GROSS ANATOMY.

A. GENERAL CHARACTERS. Note

1. The main axis, consisting of a thickened, horizontal,
under-ground stem, the rootstock, and a single vertical
branch, the aerial stem, bearing a terminal flower.

2. The rootstock, bearing as lateral appendages the roots,

■

and modified leaves in the form of broad membranous
scales.

3. The aerial stem, bearing as lateral appendages a whorl
of three leaves, and the parts of the flower.

B. THE ROOTS. Note

1. Their arrangement on the rootstock.

■

2. The almost entire absence of branching.

3. The surface, especially the transverse wrinkles on older
parts.

4. The root-hairs.

Mount a transverse section of the proximal portion of a
large root, and notice

5. The presence and relative areas of three regions:

a. The cortical region of two layers :

i. An outer layer of small cells.
ii. An inner layer of large, irregular, loose cells,

often torn through in sectioning, the unequal

TRILLIUM RECUR VA TUM. 1 99

development of which gives rise to the
wrinkling.

b. The median large-celled ox parenchyma region.

c. The central or fibro-vascular region, in which may

be detected the large openings of four or five
tracheary vessels.

Mount a longitudinal section through the center of the

root and notice

6. The several regions as before.

7. The depth of the surface wrinkles.

8. Diagram both the transverse and longitudinal sections.

C. THE ROOTSTOCK (Subterranean Stem). Note

1. The shape and thickness.

2. The succession of nodes and inter nodes.

a. The number in an unbroken rootstock.

b. The scars of former branches, and the varying

number of intervening nodes.

c. The irregular growth of the internodes.

3. The prevailing number of roots from each node.
Mount a transverse section ; notice

4. The three parts :

a. The extremely narrow brownish cortical region,

forming the boundary of the section.

b. The great mass of the stem, whitened with the

reserve food material. In thin parts of the sec-
tion, where the food material has been washed out
in mounting, note

i. The delicate colorless tissue, fundamental par-
etic hy ma.

200 TRILLIUM.

Tease a bit of the stem in a drop of water on another
slide, treat with iodine, and note

ii. The color imparted to the food material, indi-
cating its nature.
c. Scattered irregularly through the section the

comparatively few small dark areas, the fibro-

vascular bundles.

Make a longitudinal section, and notice

5. The three parts seen in the transverse section ; the
bundles branching irregularly and obscurely.

6. The growing apex. Note

a. The shape.

b. The sheathing membranous scales.

c. The position of the aerial branch.
Bisect the apex, and upon the cut surface notice

d. The two or more rather thick projecting bracts.

e. Beneath these a very small protuberance, the grow-
ing point of the stem, sometimes accompanied by
smaller lateral protuberances, the rudimentary
scales.
Draw the bisected apex.

D. THE BRANCH (Aerial Stem). Note

1. The absence of nodes below the whorl of leaves.

2. The smoothness of the surface.
Mount a transverse section. Notice

3. The three parts :

a. The very narrow cortical region.

b. The fundamental parenchyma, forming the ground

work of the section ; the cells appearing empty.

c. The limited number of fibro-vascular bundles; note

i. Their arrangement and relative size,

TRILLI UM RECUR VAT UM. 2 o 1

ii. The two areas in each : the light colored por-
tion lying toward the outside of the stem, the
phloem , the shaded portion lying toward the
center of the stem, the xylem.

4. Draw the section.

5. Make a longitudinal section and note the several parts

the

E. THE LEAF. Note

1. The scale leaves of the rootstock.

a. The bases of decayed scales at each node.

b. Younger ones, sheathing the apex of the rootstock

and base of the aerial branch.

Mount a portion of a scale and notice

c. The parallel veins, and intervening parenchyma.

d. Numerous dark spots, clusters of raphides.

2. The foliage leaves of the aerial stem.

a. The number and arrangement.

b. The shape.

c. The particular outline of the apex, and of the

base.

d. The short stalk, petiole, if present.

e. The distribution of the veins.

Mount a transverse section from near the base of the leaf,

and note

The several parts :
i. The colorless epidermis.
ii. The veins, the largest projecting on the lower

side ; each containing

111. A fibro-vascular bundle, having the phloem

area toward the under side of the leaf ; accom-
panied in the largest veins by

202 TRILLIUM.

iv. Colorless parenchyma.

v. The darkened (in fresh specimens green) tnes-

ophyll.
Mount a portion of the epidermis stripped from the upper
surface of the leaf, and beside it a portion from the under

surface. Note

g. The numerous dots in that from the lower surface,

the stomata.

h. The absence of stomata in that from the upper

surface.

F. THE FLOWER. Note

i. The several parts arranged in whorls.

a. The outer whorl of three sepals, constituting the

calyx.

b. The second whorl of three petals, constituting the

corolla.

c. The third and fourth whorls of three stamens each,

constituting the androecium.

d. The innermost whorl of three partly united carpels,

constituting the gynoecium.

2. That the parts of the flower arise from the broadened
extremity of the stem, the receptacle.

3. The alternation of the parts of each whorl with those of
the whorl next to it.

4. The sepals.

a. The shape.

b. The color in a fresh specimen.

c. The venation.

d. Draw a single sepal.

5. The petals.

TRILLIUM RECUR VA TUM. 203

a. The shape.

b. The color in a fresh specimen.

c. The venation.

a\ Draw a single petal.

6. The stamens.

a. The several parts of each.

i. The stalk ox filament, passing into
ii. The connective, on the right and left margins

of which are borne
iii. The pollen sacs, or thecce ; the connective and

thecae together constituting the anther.

b. Draw a stamen.

Mount a transverse section of the filament, along with
one of the anther, and note

c. The filament.

i. The outline.

ii. The uniform ground tissue, containing a cen-
tral fibro-vascular bundle.
iii. Draw.

d. The anther.

i. The outline of the connective, and character of
its tissues.

ii. The form of the thecal. The mode of burst-
ing is often well shown.

iii. Draw the section

e. The pollen, escaped from the thecae and appearing

as fine particles. Dust some from an anther and
examine dry, noting color and pulverulence.

7. The carpels.

a. The part's of each.

i. The enlarged basal portion, bearing a pair of
prominent ridges, united with the bases of the
other carpels to form the compound ovary.

2o4 TRILLIUM.

ii. The tapering divergent styles.
iii. The double wavy crest along the inner face of

each style, the stigma.

b. Draw the three carpels.

Make a transverse section through the middle of the

style ; mount, and notice

c. The outline, including the stigma.

d. The central fibro-vascular bundle.

e. The stigma.

\. The recurved sides t and deep median groove

extending in to the central bundle,
ii. The velvety papilla clothing its surface.
Draw the section.
Mount several transverse sections of varying thickness
passing through the middle of the compound ovary, and

notice

g. The three similar parts belonging to the three car-
pels of which it is composed, each consisting

of
i. The two prominent ridges or wings.

ii. The fibro-vascular bundle lying in the tissue

between the ridges.

iii. The sides of the carpel uniting with the sides

of the adjoining carpels, extending into the
cavity of the ovary and meeting in the center,

forming the three placentfiB.
iv. The two or more fibro-vascular bundles of the

placenta.

v. The rounded ovules in the cavity of each car-
pel, borne on the sides of the right and left
placentae.
//. Draw the section.

G. THE FRUIT. Notice

TRILLIUM RECURVA TUM. 205

1. The sepals still in growing condition.

2. The withered but persistent petals, stamens and styles.

3. The fleshy winged pod, like the young ovary, but
larger, inclosing

4. The seeds. Note

a. The slender attachment.

b. The fleshy body on the side of the seed, the stro-

phiole, which is an outgrowth of the lower part of

c. The stalk of the seed, funiculus, extending beyond

the strophiole as a ridge on the seed, the rhaphe,
and terminating at

d. The base of the seed, the chalaza

e. The shape.

The minutely granular surface.

g. Draw a seed.
Beginning at the chalaza, cut several very thin trans-
verse sections, then another transverse section from the
middle of the seed, mount, and notice

//. The thin brown coat of the seed, testa,
i. The uniform tissue within, the cells of which are

filled with reserve food material, and in the
section from the middle of the seed are seen to
radiate from the center to the outside.
j. In the sections from the base of the seed, the

small round spot, between the center of the
section and the side next the rhaphe, the embryo.

MINUTE ANATOMY.

A. THE ROOT. In a central longitudinal section
through the root-tip, note under low power

1. The outer looser cells and inner more compact tissue
forming the root-cap.1

1 It may be difficult to get the region complete.

2o6 TRILLIUM.

2. A cluster of small angular cells in the center of the
section just behind the root-cap, the primary men's fern,
forming the growing point.

3. Originating in the primary meristem, an epidermis-like
row of cells of the root proper, the dermatogen, which

■

is continuous with the epidermis .of the surface of the
root.

4. The central cylindrical mass of cells, to become the
fibro-vascular column, the plerome.

5. The region of cells between the plerome and dermato-
gen or epidermis, to become the cortical portion of the
root, the periblem.

6. The branching root-hairs and their relation to the
epidermal cells.

7. Draw the section, showing the regions above noted.

Make a transverse section of the root at its wrinkled
part. Under low power, notice

8. The peripheral portion of two or more rows of rounded
cells.

9. The underlying large-celled tissue, with delicate dis-
torted walls, often torn in sectioning.

10. The outer portion of the core, with rounded cells

becoming smaller as they lie nearer

11. The circular axial part of the core, the fibro-vascular

bundle, containing several large vessels arranged in
four or more short radiating rows.

Use a high power, and notice

12. The surface row of cells, the epidermis, slightly or not

at all differing from

13. The cells beneath the epidermis, the hypoderma.

TRILLIUM RECURVA TUM. 207

14. The very thin walls of the loose tissue.

15. The thickened walls of the outer part of the core,

and the intercellular spaces at the angles.

16. Draw a portion of these several tissues of the root.

17. The somewhat irregular row of thickened, slightly

colored cells, the bundle sheath, usually with an evident

middle lamella in the walls.

18. The fibro-vascular bundle.

a. Immediately within the bundle-sheath a row of

thin-walled cells, the per icambi urn.9

b. The radial rows of large vessels, larger toward the

center, smaller toward the periphery.

e. The intermediate groups of sieve tissue.

d. The thin-walled cells of the center of the bundle.

e. Draw the fibro-vascular bundle and bundle-sheath.
Make several longitudinal sections through the core of

the root ; identify and study

19. The several tissues seen in transverse section, drawing

a few cells of each.

B. THE ROOTSTOCK (Subterranean Stem). Make a
transverse section, mount in strong potassic hydrate, and
notice

1. The row of epidermal cells with brown outer walls.

2. The parenchyma tissue within, filled with starch, and
forming the mass of the rootstock.

3. Draw a few cells of epidermis, and of adjoining paren-
chyma.

4. The fibro-vascular bundles, cut at all angles, even longi-

* Sometimes absent in old roots by having become permanent tissue.

2o8 TRILLIUM.

tudinally. Owing to the difficulty of obtaining good
sections, and the interference of the starch, the further
study of the bundles is deferred till they are reached in
the aerial stem.
Cut a thin slice from the surface of the rootstock, and
under low power, notice

5. The shape of the epidermal cells, and absence of sto-
mata. Draw.

Make a longitudinal section through the growing tip in
the plane of the branch, and note

6. The sheath composed of one or more sets of thickened
and partly coalesced bracts. These bracts may be
detected in various stages of growth, all originating
behind

7 . The growing point.

8. The growing tips of rudimentary roots and branches. Note

the exogenous development of a branch, all the tissues

of the stem entering into it, and the endogenous devel-
opment of a root, distinct from the tissues of the stem

and pushing its way through them.

C. THE BRANCH (Aerial Stem). In a transverse section,
with a low power, notice

1. The single row of epidermal cells.

2. The loose, round-celled fundamental parenchyma, with
large intercellular spaces.

3. The fibro-vascular bundles, consisting of

a. The light colored portion, phloem.

b. The shaded portion, xylem.

Under high power notice

4. The epidermis and hypoderma. Note

TRILLIUM RE CUR VAT UM. 209

a. The thickness of the different walls.

b. Draw.

5. The parenchyma of the center of the stem. Note

a. The shape of the cells.

b. The thinness of the walls.

c. The large intercellular spaces.

d. Draw.

6. The fibro-vascular bundle. Note

a. The phloem, consisting of angular cells of various

sizes; the smaller, conducting cells or bast paren-
chyma, the larger, the sieve tissue.

b. The xylem, in the smaller bundles of less area than

the phloem, but in larger bundles greater, and
spreading out on either side the phloem, until, in
some cases, it entirely surrounds it.' It is made
up of

i. The vessels of various sizes, and
ii. Interspersed among the vessels and extending

out on the axial side, rather angular cells, the

wood pa renchyma.

7. The absence of meristem cells between xylem and

phloem, thus forming a closed bundle.

8. Draw a small and a large bundle.

Take a longitudinal section through the center of the
stem and notice

9. The several tissues seen in transverse section.

a. The epidermal and hypodermal tissues. Draw.

b. The central parenchyma. Draw.

Forming the external sheath (Prantl and Vines, Text-book, p. 58),
which is probably but a special development of the surrounding cells of
the fundamental system.

2io TRILLIUM,

c. The several tissues of the bundle.

i. The phloem, of long, thin-walled, uniform

cells. Draw,
ii. The vessels, of various sizes and kinds. Draw

some of each.

iii. The wood parenchyma, considerably like the bast

parenchyma, but in its best development with
thicker walls, and more evident somewhat

oblique end walls. Draw.

Strip some epidermis from the surface of the stem, and

under low power, notice

10. The shape and arrangement of the cells, and of the

stomata. Draw.

D. THE LEAF. Make a vertical section near the middle
of a foliage leaf, at right angles to the principal veins, and
notice

i. The row of colorless epidermal cells bounding the upper
and lower surfaces.

2. Here and there transverse sections of the veins. Note
the depression above, and the convexity below the
larger veins.

3. The mesophyll. Note

a. The layer of closely set cells along the upper side,

palisade parenchyma.

b. The loose irregular tissue on the lower side, spongy

parenchyma.

Under high power, notice

c. The shape and position of the cells of the palisade

parenchyma.

d. The shape of the cells of the spongy parenchyma

and the numerous intercellular spaces.

e. Contents of the mesophyll cells.

TRILLIUM RECURVATUM. 211

4. The epider?nis. Note

a. The shape and irregularity of the cells on the

upper side of the leaf.

b. The shape and irregularity of the cells on the

lower side, together with the shape of

c. The numerous sto?nata in transverse section, when

cut through the middle, and when through the
ends.

5. Draw a part of the mesophyll and epidermis, extend-
ing from one side of the leaf to the other.

6. The veins. Selecting a vein of moderate size, note

a. The small epidermal cells on the upper side, and

the large ones on the lower side, both more thick-
ened and regular than elsewhere on the leaf.

b. The fibro-vascular bundle, with the xylem area

toward the upper side, and the phloem area toward
the lower side* ; sometimes with

c. Fundamental parenchyma interposed between the

bundle and the epidermis on either side.

d. Draw a vein.

Strip some epidermis from the upper side of the leaf,
and some from the lower side, and notice

7. The shape and arrangement of the cells of the two sur-

faces, and the abundance of stomata. Draw.

E. THE FLOWER.

1. The sepals. Make a transverse section through the
middle of a sepal, and notice

a. The several parts and tissues seen in the leaf.

Draw.

4 Note how this follows from the relative positions of xylem and
phloem in the stem.

212 TRILLIUM.

Strip some epidermis from the upper and lower sides,
and notice

b. The shape of the cells, and presence or absence of

stomata in each. Draw.

2. The petals. Make a transverse section through the
middle of a petal, and notice

a. The several parts seen in the leaf. Draw.

Strip some epidermis from the upper and lower sides,
and notice

b. The shape of the cells and presence or absence of

stomata in each. Draw.

3. The stamens. Make a transverse section through the

middle of a filament, and at the same time through the
middle of the anther, and notice

a. The parts of the filament.

i. The epidermis, with a minutely sinuous out-
line to the free surface.

ii. The parenchyma beneath.

iii. The central fibro-vascular bundle, consisting

largely of xylem, with only a few small groups
of scattered phloem cells on the more convex
(outer) side.

b. Draw part of the filament.

c. The co?inective, with tissues like those of the fila-
ment.

d. The theca, consisting of

i. The two valves usually broken away at the

tips, springing from
ii. The base which merges into the connective.

—

e. The wall of the thecal valves. Note

i. The epidermis, like that of the filament but

with numerous stomata, seen in transverse
section.

TRILLIUM RECUR VA TUM. 2 1 3

• ii. The endot/iecium, having its cells provided with

transverse thickenings,
iii. The broken cells at the tips, corresponding to

the broken cells at the middle of the base.
The base of the theca. Note
i. The arrangement of the spiral cells,
ii. The median cavity and its extent.
g. Draw a theca in outline, and fill in a portion of the

tissues.
//. The pollen spores. Note

i. The surface of the wall, its roughness, and
the simple, large, round or oblong spots to be
seen upon some spores,
ii. The wall in optical section.
iii. Draw.
Burst some spores by pressing on the cover glass. Note

iv. The empty outer layer of the wall, extine.
v. The remainder of the spore, still enveloped by

the thin inline, roughened like the extine.
vi. The contents from broken spores, with minute

granules.

4. The carpels. In a transverse section through the style,
notice

a. The epidermis and parenchyma like that of the fila-
ment of the stamen.

b. The fibro-vascnlar bundle with apparently no

phloem, elongated to embrace the cleft of the
stigma.

c. The stigmatic surfaces, covered with papillae.

d. In some of the pollen spores lodged upon the

papillae, the developing pollen tubes may be
detected.

e. Illustrate with drawings.

2 1 4 TRILLIUM.

In a transverse section through the compound ovary notice,
under low power,

The uniform, continuous epidermis,
g. The loose parenchyma tissue of the wings and walls.
h. The fibro-vascular bundles under the sinus between

each pair of wings, and the groups in the placen-
tae. The latter give off branches to
/. The ovules, placed back to back in the ovarian

cavities. Note
i. The thick stalk, funiculus, joined to the side

of the ovule, quite inverting it (anatropous) .
ii. The two coats of the ovule, the inner protruding

from the outer,
iii. Draw.

iv. If a section passing through the center of an

ovule has been obtained, note the nucellus
within the inner coat, and

v. In the center of the nucellus the small embryo

sac.
vi. Draw.
Under high power, notice
/ The epidermis and loose parenchyma at the base

of a wing. Draw.

k. The fibro-vascular bundle of the wall, showing a

little phloem only on the outer side. Draw.
/. The parenchyma and fibro-vascular bundles of the

placentae. Draw a part.
m. Where the section has passed through the center

of an ovule, note the similarity of the cells of all

the parts. Draw.

F. THE FRUIT. So little change has taken place in the
growth of the fruit that it is only necessary to study the
minute anatomy of

TRILLIUM RECUR VA TUM. 2 1 5

1. The seed. Make several sections in succession from
the base of the seed, and an additional section from the
middle, all at right angles to the longer axis of the
seed. Note in the latter, under low power,

a. The colorless tissue, filled with reserve food mate-
rial, radiating from the center of the seed.

b. The thin brown testa.

c. The large-celled tissue of the strophioley through

the middle of which passes a fibro-vascular bundle
belonging to the funiculus.

In the sections from the base of the seed, note

d. The group of small cells lying in a cavity on one

side the center, the section of the embryo.

Under high power, notice

e. The several sections of the embryo. Draw.
In the section from the middle of the seed, notice

The colorless tissues of the center.
g. The tissues of the testa.

i. The outer layer of oblong cells.

ii. An inner layer of more elongated cells.

iii. Within this, very delicate cells, not easily

made out.
h. Draw some of the colorless cells, with adjoining

testa.
i. The tissue of the strophiole. Draw.
Take a surface slice from the seed, and notice
j. The shape of the surface cells. Draw.

ANNOTATIONS.

The most notable advance in Trillium, so far as its
gross anatomy is concerned, is the development of a

2 1 6 TRILLIUM.

complete flower.6 The so-called flower 61 Atrichum
differs essentially from a true flower in bearing the pri-
mary sexual organs (antheridia and archegonia) directly
upon the axis of the flower. In true flowers asex-
ual spore structures first arise in the shape of pol-
len spores and embryo sac, which in turn give rise to
the primitive sexual organs as naked cells within these.
The first true flowers are met with in Pinus, in which

they have no envelopes ; in Avena there is either no
perianth, or a very poorly developed one, just as we

choose to regard the palet and lodiculesas such or not ;
but in Trillium there is a typical perianth. The flower
is composed of sets of modified leaves symmetrically
clustered at the apex of a short axis. The outermost
and lowest whorl (calyx) of leaf-like sepals, a second
whorl (corolla) of colored petals, then two whorls
of stamens (andrcecium), and a central and uppermost
whorl of carpels (gynoecium), all standing upon the
broadened apex of a branch (receptacle) may be taken
to fairly represent a typical flower. The order given
not only expresses the order of occurrence upon the
receptacle but also the order of development ; and the
type number, three, so characteristic of monocotyle-
dens, should be borne in mind (see fig. I

The perianth is an arrangement for protection both
in bud and blossom,6 while in the latter stage the cor-
olla becomes in addition a device for attraction.7

5 For a concise account of the homology and nomenclature of the
parts of a flower see Sachs, Text-book, 2nd Eng. ed. , p. 490.

6 Cf.Kerner, Flowers and their Unbidden Guests.

1 Cf. Gray, Struct. Bot., p. 215, etseq.: Darwin, Fert. of Orchids ;
Effects of Cross and Self-fertilization ; Forms of Flowers etc.

TR1LLI UM RE C UR VA T UM. 2 1 7

While this is generally true throughout phanerogams,
there are cases in which the calyx becomes attractive,
and other cases in which the calyx and corolla have so
far lost their original functions that they neither attract
nor protect.

In the blended carpels, forming the pistil which in-
closes the ovules, we have the characteristic feature of
angiosperms as distinguished from gymnosperms. In
A vena the ovule is adherent to the wall of the ovary,
but in Trillium it is distinct; the whole after fertilization
forming the fruit with its inclosed seeds. Each carpel is
an infolded leaf, bearing the ovules upon its edges
(see fig. 11). Each should normally, then, contain two
rows of ovules, corresponding to the right and left
margins of the leaf, as in fact is the case in Trillium.
These lines of attachment, the theoretical leaf margins,
are known as placentae. The upper part of the carpel-
lary leaf is generally modified to form a long or short
style, while the stigma is a surface formed of cells se-
creting a viscid fluid, and more or less modified for the
reception and retention of pollen.8

The nucellus is the part of the ovule to appear first,
followed by the inner and outer integuments in the order
named (basipetal). Concerning the homology of the
ovule there has been and still is much discussion, and the
student desiring to pursue the subject must look to its
extensive literature.9 The anatropous ovule of Tril-

8 IT

For discussion of the pistil and carpel, and references to the litera-
ture of the subject, see Gray, Struct. Bot, pp. 166 (with footnotes), 259,
et seq.

9 Gray, Struct. Bot., pp. 267, 282; Eichler, Bluthendiagramme,
part II, page xv; Warming, De l'Ovule, Ann. Sci. Nat., ser. 6, v, p

Eng. ed., pp. 492, 570, etc.

5, xii, p. 312 ; Sachs, Text-book, 2nd

2 1 8 TRILLIUM.

Hum may be mentioned as by far the most common
form.

As in Adiantum, the main axis of Trillium is subter-
ranean, horizontal and thickened, forming a rootstock,
a protective measure which in this case is correlated
with spring blooming and a long period of rest. The
aerial part of Adiantum, however, is a leaf, while in
Trillium it is a branch, the " root-leaves " being

reduced to membranous scales on the rootstock. A
single branch (rarely two) is sent above ground each
season, and a series of corresponding annual scars may
frequently be seen upon the stem. In the meantime
the terminal bud of the latter continues to develop
and to thrust its way through the soil, protected in
this root-like habit by a special modification of bud-
scales.

Probably the most exceptional character of Trillium
is the venation of its foliage leaves, which is of the
netted type, instead of the parallel venation most
characteristic of monocotyledons, as in Avena. Among
net-veined leaves they are palmate, a type which pro-
duces a broad expanse of surface, very favorable for the
accomplishment of leaf work. In this way Trillium has
secured a large exposure of surface to air and sunlight
for a plant so low in stature, and generally deeply sunk
in vegetable debris.

The primary root-structure is quite uniform in all
plants, consisting of epidermis (or a piliferous layer),
cortical parenchyma, and a central fibro-vascular cylin-
der. In the central cylinder xylem and phloem masses
alternate with each other, the intervening spaces being
occupied by parenchyma (forming a radial bundle) ; sur-

TRILLIUM RECUR VA TUM. 2 19

rounding all is a layer of parenchyma* the pericambium,
and outside of this a single layer of modified cortical
cells, the bundle sheath or endodermis. Rootlets of
most cryptogams originate from the bundle sheath,
while in phanerogams they usually come from the peri-
cambium.10 In the radiating lines of tracheary vessels
it will be noticed that the larger vessels are toward the
center, the smaller spiral vessels being peripherally
placed, thus reversing the order of the stem.11

The stem is very much modified by becoming a food
reservoir. The epidermis is poorly limited, often
scarcely distinguishable from the adjacent cortical
parenchyma ; the parenchyma of the fundamental
system is greatly developed and filled with starch ;
while the fibro-vascular bundles are reduced and
irregular in their course. In most cases the bundles
bend outwards, and such are evidently leaf-traces,1*
though they have lost all definite connection with the
accompanying scale-like leaves.

The terminal bud of the stem is large and its parts
very distinct. It is taken to represent in our series a
typical terminal bud of phanerogams. A section
reveals the fact that the growing point (pwictum vege-
tationis) consists of a group of cells, in place of the
single apical cell of cryptogams, and the forming tis-
sues diverge from it in well defined lines. The three
typical regions of the stem originate from different
regions of this primary meristem, so that they do not

10 Prantl and Vines, Text-book, p. 51; Strasburger, Bot. Pract., p. 276.

11 Cf. Goodale, Physiol. Bot., p. no, et seq. ; Prantl and Vines, Text-
book, p.5i;DeBary, Comp. Anat., p. 348.

18 Cf. Prantl and Vines, Text-book, p. 46; Goodale, Physiol. Bot., p.
125; DeBary, Conip. Anat., p. 233.

220 TRILLIUM.

have a common origin, but are distinct from the first.
Lateral members soon appear as small protuberances,
which are rudimentary leaves, branches, or roots, those
nearest the apex being the youngest. The axis
remains so short that the lower leaves overlap the
growing point, and in the case of this underground stem
thicken and coalesce at their tips, forming a continuous
and firm sheath, thus performing the same office of pro-
tection for the rootstock that the root-cap does for
roots. In the same Trillium bud may be seen the
essentially different mode of development of the root
and branch, the former being endogenous and pushing
its way through the overlying tissues, the latter exog-
enous,18 blending with the surface tissues of the stem.

The branch, or aerial stem, is remarkable for its sin-
gle long internode. The fibro-vascular bundles are
rather poorly developed, the monocotyledonous stem
bundle being more typically represented in Avena. In
Trillium, however, are seen such monocotyledonous
characters as the isolation of the bundles within an
abundant fundamental parenchyma, the well-marked
phloem and xylem areas with no intervening cambium
(closed bundles), and an occasional development of an
external sheath.14

The histology of the leaf is in general much the
same as in the majority of leaves ; it differs from Avena
in the presence of a much better developed mesophyll.
A broader expanse of leaf tissue necessitates a greater
branching of the supporting and conducting fibro-vas-
cular system, and a better differentiation of leaf sur-

Prantl and Vines, op. cit., p. 23.
Prantl and Vines, op. cit., p. 58.

TRILLIUM RECUR VA TUM. 2 1 1

faces. Hence the palisade and spongy parenchyma
are quite distinct, and the large intercellular spaces of
the latter have more frequent connection with the
outer air through stomata. The fact that in the
fibro- vascular bundles of leaves the xylem is always on
the upper side, and the phloem on the lower, should
be recognized as necessitated by the relation which
they hold to the same regions in the stem.

In the ovary the distribution of fibro- vascular bun-
dles and the relative positions of phloem and xylem
are most interesting and suggestive. The single bun-
dles in the outer walls have the phloem toward the
outside (the lower surface of the carpellary leaf), and
the xylem toward the inside. But the inner group of
bundles in the ovarian partitions have their arrangement
reversed, the phloem being on the inside (toward the
center of the flower) and the xylem on the outside 16
(see fig. 10). This is readily accounted for by the in-
folding of the carpellary leaves (see fig. 1 1).

The walls of the ovary show also a region of very
loose spongy tissue, developed in the mesophyll of the
carpellary leaf, and extending into the style, the con-
ducting tissue, " which serves as a path of least resist-
ance for the penetrating pollen tubes." ,8

16 Cf. Goodale, Physiological Botany, p. 173.
16 Goodale, Physiol. Bot , p. 172.

SHEPHERD'S PURSE.

Capsella Btirsa-pastoris Moench

PRELIMINARY.

This plant, chosen to represent the highest develop-
ment of plant life, is of European origin, but has
become abundant in this country and elsewhere, being
one of those vigorous foreign species which hasten to
take possession of any cleared or cultivated land. It is
found everywhere around dwellings, and in fields and
waste grounds. It has not only the advantage of uni-
versal distribution, but also of continuous growth
throughout most of the year, even a few warm days in
winter calling it into bloom. One who does not already
know the plant can recognize it from the fact that it is a
low, quite insignificant herb, varying in height from five to
fifty centimeters (two inches to a foot or two), with a ro-
sette of rather narrow jagged root-leaves often lying flat
upon the ground, much smaller scattered stem-leaves,
and very small white flowers constantly opening at the
summit of the branches, and producing small triangular
rather heart-shaped pods below (see fig. 6). It is most
abundant in spring and early summer, but can be found
in bloom throughout the warm months, and may be
grown in the green-house for use in winter.

CAPSELLA BURSA-PAST0R1S. 223

The materials needed for studying are alcoholic (or
fresh) specimens of roots, stems, leaves, flowers, and
pods ; fresh specimens of flower buds ; and potassic
hydrate.

LABORATORY WORK.

GROSS ANATOMY.

A. GENERAL CHARACTERS. Note

1. The main axis, consisting of a root and stem.

2. Three kinds of branches :

a. One on the root, rootlets.

b. Another on the stem and simply repeating it, long

or very short, or represented by small buds.

c. The third on the upper part of the stem, each

bearing a single flower, pedicels.

3. The position of the stem branches with reference to
the stem leaves, axillary.

4. The nodes and intemodes of the stem, as indicated by
the insertion of the leaves.

5. The absence of lateral appendages on the root or its
branches ; those of the stem and its branches appear-
ing as foliage and flower parts.

6. The absence of leaves or bracts subtending the pedi-
cels.1

B. THE ROOT. Clean thoroughly, immerse in water
over a dark surface, and note

1. The arrangement of the branches (rhizotaxy).

2. The thickened whitish tips of uninjured rootlets.

1 A notable peculiarity of the order Crucifera, of which Capsella is a

member,

224 SHEPHERD' S PURSE.

3. Color as contrasted with that of the growing stem.

4. The root-hairs near the tips of rootlets.

Make transverse and longitudinal sections of a medium
sized root and note the presence and relative importance of

5. The three tissue regions :

a. The thin peripheral or cortical region.

b. The large axial or central cylinder, in which radi-
ating lines formed by large ducts can usually be
seen in the transverse sections.

■

c. A region of loose colorless cells between the other

two regions.

.Peel the outer layers from a branching root, and notice

6. The axis of each rootlet remains attached to the axis
of the main root.

C. THE STEM. Note

1. Mode of branching.

2. Surface markings.

3. The relative lengths of internodes

4. Axillary branches or buds.

Make a transverse section and note

5 . Three regions :

a
b.

The peripheral or cortical region.

The narrow median or fibro-vascular region

c. The axial or pith region?
6. 'Wit fibro-vascular bundles. Note

a. Shape and relative size.

b. The cut ends of the tracheary vessels, as holes

through the bundles.

8 Not present in the root.

CAP SELLA BURSA-PASTORIS. 225

7. Draw the section.

Make a longitudinal section through a branch and leaf-
bearing node, and note

8. The three regions, as well as

9. Their relation to the leaf and branch.
10. Illustrate with diagram.

D. THE LEAF. Note

1. Two sorts of leaves :

a. Root-leaves, clustered at the base of the stem.

b. Stem-leaves.

2. Leaf arrangement (phyllotaxy). Observe that an imagi-
nary line connecting the insertions of successive stem
leaves is a spiral. Discover the number of times the
spiral encircles the stem, and the number of leaves it
passes, before reaching a leaf standing directly over the
first.3

3. Leaf parts ; in the root-leaves a blade and leaf-stalk or
petiole, in the stem-leaves simply a sessile blade.

4. Leaf shapes and sizes, the great variety. Draw a series
of the most characteristic.

5. Leaf surfaces j differences between the upper and
lower. Notice

a. Simple hairs.

b. Stellate hairs.

6. Distribution of the veins, and their relation to the teeth.

7. The uncoiling of the spiral threads, when the leaves are
broken by careful stretching.

3 The student may find it easier to substitute a thread for the imagi-
nary line, and must also allow for any twisting of the stem.

226 Shepherd* s pur se.

E. THE FLOWER. Note

i. The four sets of organs and the number of parts in each.

2. The receptacle, the enlarged end of the stem.

3. The sepals.

a. The number of whorls.

b. The shape.

c. The color in fresh specimens.

d. Draw a single sepal.

4. The petals.

a. The number of whorls.

b. The shape.

c. The color in fresh specimens.

d. Draw a single petal.

5. The stamens.

a. The number of whorls, and number of stamens in

each.

b. The lengths and positions compared with one

another.

c. The position of the long pairs and short single

stamens with reference to the petals.

d. The four greenish elevations on the receptacle,

nectaries, alternating with the paired and single
stamens.

e. The filament, to the tip of which is attached

The anther. Note

i. The two thecoz.

ii. The very narrow connective.

iii. The lines of dehiscence (best seen in the anther

of an advanced bud).

iv. The shape of apex and base.

v. The different appearance of the inner and

outer faces.

CAPSELLA BURSA-PASTORIS. 22 7

vi. With a needle gently break open the thecae,

and, mounting dry, note the abundance, color,
and pulverulence of the pollen,
g. Draw an uninjured stamen.

6. The pistil. In a just opened flower, note

a. The shape.

b. The three parts, stigma, style, and ovary.

c. The ovules.

d. Draw an uninjured pistil.

7. Construct a diagram (like fig. 1) to show the relation
of the parts of the flower to each other.

F. THE FRUIT. Taking the oldest well-formed pod,

note

1 . The shape.

2. The median ridge of each flattened face extending into
the persistent style.

In a transverse section of a pod note

3. The partition formed by the inward projection of the
two placental

Open a pod by pulling away the two valves from the
ridge, and note

4. The shape of the valves.

5. The membranous partition.

6. The seeds. Note

a. The funiculus and its attachment.

b. The roughened surface, best seen in dry seeds.

c. The shape, appearing curved upon itself, campy-

lotropous.

d. Draw a seed showing its attachment.

2 2 S SHEPHERD' S PVR SE.

At the free end of as old a seed as possible, tear the seed-
coats slightly, and by careful pressure force out

e. The embryo. Make out the relations of

i. The seed-leaves, the cotyledons.
ii. The initial stem, the caulicle.

Draw the embryo.
In a transverse section across the long axis of the seed,
note

g. The seed-coats.

h. The cut faces of the two cotyledons, rather flat

and in contact with each other.
/". A section of the caulicle, at the narrower end of

the section, and lying against the back of one

cotyledon (incumbent).
J. Diagram the section.

MINUTE ANATOMY.

A. THE ROOT.

i. The rootlets. Remove some of the smallest rootlets,
examine with a high power, and note

a. In complete rootlets, the root-cap.

b. Behind the root-cap the central cluster of mer-

istematic cells, from which diverging rows of cells

pass off, gradually merging into

c. The permanent tissues of the rootlet.

d. The root-hairs ; the portion of the root on which

found.

e. Make a diagram of the tissues of the root-tip, and

also draw some root-hairs accurately.

Make a transverse section of a very small rootlet,4 examine

4 Secondary changes take place so rapidly in the roots of Capsella, that
some difficulty may be experienced in finding one with typical primary
root structure ; very young rootlets should therefore be selected for exam-
ination.

CAP SELL A BURSA-PASTORIS. 229

with a high power, and note

A peripheral region, consisting of the epidermis/

and a few layers of hypodermal cells.
g. A median region of colorless cells, the cortex.
//. Within this a single row composed of somewhat

smaller, more closely packed cells, the bundle sheath,
i. The space inclosed by the sheath entirely occupied

by the fibro-vascular region, in which note
i. The two xylem masses, placed with their inner
ends of larger cells in contact, thus dividing
the region into similar halves (binary).
ii. The two phloem masses, placed right and left

of the xylem.
iii. A limited amount of parenchyma, separating

the xylem and phloem portions from each
other, and both from the bundle sheath.
j. Draw the whole section.
A series of ^transverse sections of larger and larger root-
lets will show secondary changes, characteristic of dicoty-
ledons, up to

2. The main shaft. Make a transverse section, examine
with a low power, and note

a. The entire disappearance of epidermis.

b. The cortical parenchyma.

c. The fibro-vascular cylinder.
Using a high power, note

d. The cortical parenchyma arranged in radiating lines,

from the tangential and radial division of its
meristem cells. The outer layers may be com-
posed of thin-walled, close set, squarish cells, cork ;
within which are often other layers of larger cells,
much distorted from the pressure under which the

5 The epidermis may have disappeared even in a very small rootlet.

230 SHEPHERD'S PURSE.

root grows. Any of the cortical cells may have
thickened walls.
e. The alternating xylem and phloem masses. In com-
parison with the sections under A. 1. note
i. The increased number and irregularity of
xylem and phloem rows, making longer and
shorter radial rows, quite obscuring the
primitive arrangement,
ii. An almost complete disappearance of inter-
vening parenchyma, xylem and phloem being
in close contact.
Draw a segment showing the tissues noted.
Make a radial longitudinal section, and using a high

power,

g. Compare thoroughly with the regions of the trans-

verse section.

//. Illustrate with drawings.

B. THE STEM. Make a transverse section, examine with
low power, and note

1. Three regions :

a. Cortical region.

b. Fibro-vascular region.

c. Pith.

2. The fibro-vascular bundles ; shape and relative sizes.
Examine with a high power, and note

3. One row of epidermal cells, with very thick outer and
inner walls. Note

a. The cuticle.

6 Several sections will be needed to show all the regions of the fibro-
vascular area.

CAPSELLA BURSA-PASTORIS. 231

b. Sections of stomata.

4. Several rows of parenchyma cells.

5. Usually one row of tolerably large, nearly empty paren-
chyma cells, the bundle sheath (best distinguished in
section from growing plant).

6. The masses of fibrous tissue rising between the outer

portions of

7. The fibro-vascular bundles ; selecting one of the largest
of these, note

a. The arch of bast fibers ; compare this region with

the same in smaller bundles.

b. Beneath the arch a cluster of smaller irregular cells,

soft bast.

c. The tracheary tissue and wood fibers composing the

xylem.

8. The position and extent of the/////, the regularity of
the cells and the intercellular spaces.

9. Draw a segment of the section containing at least one
bundle.

Make a radial longitudinal section, including a fibro-vas-

1 1

*3
14

r bundle,7 examine with a high power and n<

The epidermal cells.

Parenchyma.

Bundle sheath of squarish cells.

The bast fibers, length and nature of walls.

Soft bast, shape and walls.

Tracheary vessels, variously marked.

1 In a section which passes between nbro-vascular bundles, the same
regions will be noted, except that 13, 14, 15, 16 are replaced by abundant
fibrous tissue.

232 SHEPHERD1 S PURSE.

1 6. Wood fibers, length and nature of walls.

17. Pith parenchyma, character of walls.

18. Draw the various tissues.

C. THE LEAF. Make a transverse section of a radical
leaf at right angles to the midrib, examine with a high
power, and note

1. The epidermis, consisting of one row of empty cells on
the upper and under surfaces of the leaf. Observe

a. Sections of stomata. Draw.

b. Hairs of various kinds. Draw.

2. The mesophyll, consisting of

a. An upper row of oblong cells with longer axis at

right angles to the plane of the leaf, palisade paren-
chyma.

b. A lower region of rounded loosely aggregated cells,

spongy parenchyma, with large and small intercel-
lular spaces, those in connection with the stomata
being especially large.

3. The fibro-vascular system. In the section of the midrib
note

a. The position of the phloem and xylem areas with

reference to the leaf surfaces.8

b. The tissues in each as compared with those of the

stem bundles.

In sections of the veinlets note

c. The tissues that persist.

4. Draw a transverse section of the leaf, illustrating all

the observed facts.

8 Note how these positions follow from the relative positions of xylem
and phloem in the stem,

CAP SELLA B URSA-PASTOR IS. 233

Mount a portion of the epidermis of both surfaces of the
leaf, and note

5. The epidermal tissue.

a. Shape of the cells.

b. Hairs of two kinds.

c. Stomata, comparative abundance on the two sur-

faces.

d. Often dark sheaf-like masses of raphides, torn out

from underlying cells.

e. Illustrate with drawings.

D. THE FLOWER.

1. The sepals. Mount a sepal, examine with a high power
and note

a. Venation.

b. Epidermal cells, their shape and striation.

c. Presence or absence of stomata.

d. Make a drawing, showing these characters.

2. The petals. Mount a petal, and note

a. Venation.

b. Epidermal cells of the tip and base, their shape and

striation.

c. Presence or absence of stomata.

d. Draw.

3. The stamens. Make a transverse section through a fil-
ament and also through an anther of an advanced bud,
examine with a high power, and note

a. The structure of the filament.

i. The epidermis,
ii. The parenchyma beneath.

9 This can best be done by making a section of the entire bud.

2 34 SHEPHERD' S P URSE.

iii. The fibro-vascular bundle, comparing its tis-
sues with those in the stem bundles.

b. The two thec<z> each consisting of two valves.

c. The wall of the valves, consisting of

i. The epidermis.

ii. The endothecium, an elastic inner row of spir-
ally thickened cells.

d. Draw a section of a theca showing its tissues.

e. The pollen. Note

i. The surface of the wall.

ii. The two layers of the wall : the extine col-
ored and with thin spots ; the intine thin and
colorless.
By careful pressure upon the cover glass, there can be

seen

iii. The intine unbroken, but protruding through

one of the thin spots in the extine, the
true character of the wall becoming thus very
obvious.

iv. The minutely granular contents.

4. The pistil. Mount a slice from the surface of the
stigma and also a transverse section of the ovary, both
cleared with potash, and note

a. The

i. Its surface, with pollen tubes sometimes pene-
trating it.
ii. Draw.
b. The ovary.

i. The epidermal cells,
ii. The character of the mesophyll.
iii. The fibro-vascular bundles, their position and

tissues,
iv. The structure of the placentae.

CAP SELLA B URSA-PA STORLS. 235

v. The structure of the false partition,
v i . D raw.

c. The ovules.

i. In favorable sections the pollen tubes may be
seen entering the ovules. These are easily
recognized, as the tube breaks off some dis-
tance from the micropyle.

ii. The fibro-vascular bundle of the funiculus

terminating in the ovule.

iii. The two integuments, distinct from each other

beyond the bend,
iv. The nucellus, containing a large cavity, the

embryo sac, which follows the curve of the

ovule. Within the embryo sac

v. The embryo, in various stages of development.

vi. Draw, showing all the above facts.

The following phases in the development of the embryo

can not be seen in alcoholic specimens, but may readily be

traced in fresh ones by the use of potash as a clearing agent.

d. The embryo. Mount some cleared ovules from an

advanced but unopened bud, press slightly upon
the cover glass, and note

i. The large curved embryo sac.

ii. In the end of the sac nearest the micropyle, a

roundish or oblong cell, the oosphere.
iii. At the opposite end of the sac, a mass of

cells projecting into it.
Mount ovules from an open flower, treat as before, note

iv. In place of the oosphere a chain of cells, the

pro-embryo, with the basal cell usually much

swollen and with a group of cells at the free
end of the chain, the forming embryo.10

The endosperm, which develops rapidly in angiosperms after fertili-

zation, is too transient in this case to make out satisfactorily.

2 3 6 SHEPHERD' S P URSE.

From this point the development of the embryo may be
traced with greater or less particularity, by examining
ovules in various stages of advancement, until the following
condition is seen in seeds from a young pod :

v. The pro-embryo has disappeared,
vi. The embryo nearly fills the embryo sac, the

cotyledons beginning almost exactly at the

bend,
vii. Make drawings illustrating this development.

E. THE FRUIT. Make a tranverse section through as
old a fruit as possible, clear with potash, and note

i. The nature of the epidermis, mesophyll, fibro-vascular
bundles, placentae and partition, compared with that
studied in the ovary.

2. The seed. In transverse sections of seeds note

a. The testa, its color and structure.

I). The thin-walled tissue filled with food material.

c. The cotyledons, the nature of their tissues as com-
pared with those of the leaf.

d. The caulicle, its structure and tissues as com-
pared with those of the stem. Draw.

e. Draw a complete section of the seed, filling in

enough of the tissues to indicate their character.

ANNOTATIONS.

Capsella very well presents in a compact form the
salient features of a dicotyledon. The paired cotyle-
dons, net-veined leaves, four-parted flowers, and con-
tinuous fibro-vascular zone of the stem, all mark it as a
member of this highest group.

CAP SELLA BURSA-PASTORIS. 237

The primary root continues the plant axis below
the surface of the ground in the form of a tap root, and
thus enables the plant to take a deep and firm hold
upon the soil. Such primary roots are best developed
in dicotyledons and gymnosperms, remaining small in
monocotyledons and pteridophytes.

The foliage, instead of being somewhat evenly dis-
tributed along the stem and its branches, is largely
collected at the surface of the ground in a cluster of
so-called root-leaves. The toothed and lobed outline
of the leaves with reticulated venation is quite charac-
teristic of dicotyledons. In Trillium (an anomalous
monocotyledon in this regard) there was presented the
palmate type of net-veined leaves, while in Capsella
we find the pinnate type, tending to narrower and
longer leaf forms.

An exceptional feature of Capsella (and other
Criiciferce) is the entire suppression of bracts in the

flower cluster, giving the pedicels (branches) the
appearance of originating from the main axis without
subtending leaves.

The structure of the flower is not typical of dicotyle-
dons, in which the type would be better expressed by
an arrangement like that of Trillium, after substituting
five for three as the type number. As a member of the
Criiciferce, however, Capsella has two whorls of two
sepals each, the lower (outer) being median (in the

plane of the axis) and the inner lateral ; one whorl of
four petals, alternating with the .four sepals ; two

whorls of stamens, the outer and shorter pair lateral,

the inner and longer set composed of four stamens,

arranged in axial pairs(tetradynamous) ; and one whorl

2 3 S SHEPHERD' S P URSE.

of two carpels laterally placed. There has been much
discussion concerning the cruciferous flower, chiefly as
to its six stamens and single whorl of four petals. The
most natural explanation seems to be that which
makes two the type number throughout, the inner
whorl of stamens and the single whorl of petals each
becoming four by chorisis.11 The morphological sig-
nificance of the small glands among the stamens at the
base of the ovary is uncertain.12

The bi-carpellary ovary becomes two-celled by a
membranous outgrowth connecting the two opposite
parietal placentae. This outgrowth, not being a usual
part of the carpels, is considered a false or spurious
partition. When the fruit (a silicle) opens, the two
valves split away from this false partition, to which the
placentae and hence the seeds remain attached.

No part of vascular plants has so constant a charac-
ter as the root. The root-cap and root-hairs, most
characteristic root structures, are much alike in all
cases. The primary arrangement of the tissues in
pteridophytes, gymnosperms, monocotyledons, and
dicotyledons is upon the same plan throughout. The
original number of xylem and phloem masses is quite
limited in dicotyledons, ranging from two of each (bi-
nary, as in Capseila) to eight, but is not constant ; while
in monocotyledons it is generally larger. In dicotyle-
dons and gymnosperms the root increases in thickness
by secondary growth which eventually produces great

11 Gray, Struct. Bot, p. 206, with reference to the views of Eichler,
Kunth, Henslow, and others ; Strasburger, Bot. Pract , p. 587 ; Eichler,
Flora, 1865, p. 497, and 1869, p. 97 (both with plates) ; Bluthendia-
gramme, ii, p. 200, where the literature is cited.

l* Cf. Hildebrand, Prings. Jahrb., xii, p. 10 ; Miiller, ibid, p 161.

CAP SELLA BURSA-PASTORIS. 239

changes in the primary structure. Certain of the deli-
cate parenchyma cells lying between the xylem and
phloem elements undergo repeated division, producing
wood and bast tissue. The layer of cambium cells thus
begun on either side of the original plate of xylem soon
unites with its neighbor at the ends, and forms a closed
cambium ring. This ring has the properties of the
cambium layer of the stem, as in Pinus, and by means
of it the root is enabled to increase in thickness
to any extent. It does not, however, as in the
stem, produce its phloem exclusively on the outside and
xylem on the inside of the ring, but they lie side by
side in radiating lines, the number of these lines
increasing with the increase in circumference.13

The fundamental system in the stem of dicotyle-
dons is much more differentiated than is usual in mon-
ocotyledons. It is divided into an inner and outer
region by the fibro-vascular system, in the latter of
which various tissues may be developed, such as col-
lenchyma, fibrous tissue, etc. In the case of Capsella
the principal modification of the parenchyma of the
fundamental system is the development of the abun-
dant fibrous tissue (sometimes referred to scleren-
chyma), which embraces the xylem of the bundles
and arches between the phloem areas. In the fibro-
vascular system the chief characters of the dicotyle-
donous stem appear. The wedge-shaped bundles are
not scattered through the fundamental tissue, but
are arranged in a zone concentric with the surface of

13 On the secondary thickening of roots see DeBary, Comp. Anat , p.
473 ; Goodale, Physiol. Bot, p. 113 ; VanTieghem, Ann. Sci. Nat., ser.
5, xiii, p. 185.

240 SHEPHERD' S PURSE.

the stem, and inclosing the inner region of the funda-
mental tissue, the pith. The parenchyma rays
(medullary rays) left between the bundles may be

broad or narrow. The arrangement and course of the

bundles depend largely upon the position of the leaves.
From each leaf one or more bundles enter the stem
and passing downward finally become part of the fibro-
vascular zone. Transverse sections of the stem often
cut across bundles midway in their course from the
leaf to the vascular ring, and they then appear as if
belonging to the cortex. The bundles are collateral,
with a cambium layer between the xylem and phloem,
forming the characteristic open bundle of dicoty-
ledons. In Capsella a bundle-sheath arches over each
bundle, and frequently becomes continuous around
the entire fibro-vascular zone.14 In the xylem the
spiral and annular vessels are the oldest and most
centrally placed, the dotted ducts, the largest elements
of the xylem, occurring nearest the phloem 16

The leaf shows the general dicotyledonous charac-
ters of more contorted epidermal cells and more num-
erous and smaller stomata. The fibro-vascular bun-
dles are like those of the stem, tracheides replacing
other vascular elements in the ultimate ramifications.

Capsella is so favorable for the study of the
development of the embryo, that this very import-
ant subject has been deferred until now. It has
already been seen how the asexually produced pollen
spore (microspore), after falling upon the papillated

14 Pointed out by Kamienski, in DeBary's Compar. Anat., p. 415.

15 For stem structure see Prantl and Vines, Text-book, p. 47 ; Bessey,
Bot., p. 438 ; Goodale, Physiol. Bot, p. 119.

CAP SELLA BURSA-PASTORIS. 241

surface of the stigma, develops a pollen-tube and pene-
trates the tissues of the style. The rate of descent of
the pollen-tube is quite various in different plants. In
the style and walls of the ovary there is usually a
region of least resistance to penetration, furnished by
the delicate " conducting tissue," or the style is
frequently tubular (as in Viola). In Capsella, very
soon after pollination, an abundance of pollen-tubes is
found in the ovarian cavity. Some of them may be
seen to have entered the micropyles of the ovules and
penetrated to the nucellus.

The preparation of the ovule for fertilization has
been the development, at the apex of the nucellus, of
the embryo sac (macrospore), at the micropylar end of
which lies the oosphere (embryonal vesicle), accompa-
nied usually by two similar masses, the synergidae. At
the base of the embryo sac appear three or more free
cells, the antipodal cells ,e of Hofmeister. The six
cells which differentiate into the antipodal cells,
oosphere and synergidae, constitute a very rudimentary
prothallium,17 which is far more reduced than in gym-
nosperms, but corresponds to the primary endosperm
of these plants. The endosperm (of most text-books),
more properly secondary endosperm, is produced by
cell-formation around the nuclei arising from division
of the definitive nucleus of the embryo sac.1* When

16 Strasburger, Bot. Pract., p. 522, et scq. ; Prantl and Vines, Text-
book, p. 205.

17 Sachs, Text-book, 2nd Eng. ed., p. 582, where a fuller account

of the changes preliminary to fertilization in angiosperms may be
found .

18 Sachs, Text-book, 2nd Eng. ed., p. 585.

242 SHEPHERD'S PURSE.

fertilization19 has taken place a membrane is devel-
oped about the oosphere, making it a sexual spore.

By divisions20 in one plane the oospore at once
extends toward the interior of the ovule as a chain of
cells, the suspensor or pro-embryo, the basal cell of
which becomes large and bladder-like. The apical cell
at the free end of the suspensor, by repeated division
in several planes, forms a cell mass, which presently
assumes the form of the embryo.21 The ovule after
various changes of minor importance in this connec-
tion becomes at last a ripe seed.

For an account of the nuclei of the pollen spore and oosphere, and
their union in the fertilizing act, see Strasburger, Neue Untersuchungen.

2Q For methods of cell division in the developing embryo of Cap-
sella (with figures) see Bessey, Bot. , p. 424 ; Westermaier, Die ersten
Zelltheilungen im Embryo von Capsella, Flora, 1876, p. 483.

iJ1 For further description of the development of the embryo see Gray,
Struct. Bot., p. 283 ; Prantl and Vines, Text-book, p. 204 ; Bessey, Bot.,
p. 423 ; Sachs, Text-book, 2nd Eng. ed., p. 585.

GLOSSARY.

Yb-stri c-tion (ab, off ; stringo, / tie).
Partial or complete separation by con-
traction.

A-liat-ro-poUH (ava% up; Tpeirw, /

turn). Said of an inverted ovule or
seed which has the rhaphe extending
its whole length.

Aii-riroB'-ci-um (airjp, a male ; oI*o?,
a house). The stamens of a flower
collectively.

A ii nu-lurt (annulus, a small ring).
The elastic ring of cells around the
sporangium in ferns.

A ii ther iap0T7p6$, flowery). The pol-
len-bearing part of the stamen.

An-ther-i'd-i am, pi. antheridia
(anther; cZ£o?, form). The male or-
gan of the lower groups, analogous to
but not homologous with the anther

of phanerogams.
A'n-ther-o-zoids (anther; £wor, an
animal ; clfios, form). The male re-
productive bodies developed in an-
theridia.

A'n-tho- tax-y (ai>9osy a flower ; -rafts,
arrangement). The arrangement of
flowers in a cluster ; inflorescence.

An-ti'p-o~dal (airi, over against ;
ttous, afoot). Said of a group of cells
at the end of the embryo-sac furthest
from the micropyle.

A'p-i-cal (apex, the top). At the apex

or tip.

A-po'ph-y-sis (ano,from ; </>u<ris, na-
ture). In mosses, an enlargement of
the pedicel at the base of the capsule.

Arch-e-go'n i-um, pi. archegonia

{ap\rj. beginning: yowij, offspring).

The female organ of bryophytes and
pteridophytes.

A- re'-o-la, pi. areolae (areola, a smalt
open space). The spaces in a reticu-
lated surface, as in the thallus of
Marchantia.

A'a-co-spores. The spores formed in
an ascus.

A'a-cua, pi. asci (aoxoc, a sac). The

spore sac of a large group of carpo-

phytes.
A'x-i-al. Relating or belonging to the

axis.
A'x-il (axilla, the arm-pit). The point

just above the attachment of a leaf to
the stem.
A'x-is (axis, an axle-tree). The cen-
tral part or longitudinal support on
which organs or parts are arranged.

I last (bass). In general, the phloem
region of a fibro- vascular bundle : or,
specifically, the fibers of the phloem.

Bract (bractea, a thin plate). The
more or less modified leaves of a
flower cluster.

Bry-o'ph-y-ta (Ppvov, moss; 4>vtqv% a
plant). A primary division of plants,
named from its principal group, the
mosses. Bry'-o-phyte is the English
equivalent.

Bu'l li-form (bulla, a swelling). Said
of enlarged or swollen cells.

Ca' 1-1 us (callus, a callosity). A hard-
ened or thickened place ; technically
used of the thickening mass in a sieve-
plate, usually appearing as a layer on
each side of the plate.

244

GLOSSARY.

tra

mosses, the hood which covers the

capsule.
Ca'-lyx (calyx, a cup). The outer en-
velope of a flower, composed of sep-

als,
bium.

Resembling cam-

The

Ca'm-bi-um (cambio, / exchange).
The meristem cells of an open fibro-
vascular bundle, lying between the
phloem and xylem, which retain the
power of division.

Cam-py-lo't-ro-pous (/cap.7r>7, bend-
ing; rpe'irca, / turn\. Said of an ovule
or seed which becomes curved in its
growth so as to be inverted.

Ca'p-sule (capsula, a small box). A
dry dehiscent seed-vessel (formed of
more than one carpel) ; or a similar

spore-vessel.

Ca'r-pei (Kap7ros, fruit). The con-
stituent leaf of a pistil • hence either a
simple pistil, or one of the parts of a
compound pistil.

Ca'r-pel-la-ry. Relating to a carpel.

Car-po-go'-ni-um, pi. carpogonia

(/cap7T05, fruit ryovrj, offspring).
female organ of carpophytes.

Ca'r-po-pliyll (/capiros, fruit ; (f>v\\ov^

a leaf). The carpellary leaf.

Car-po'pli-y-ta (*ap7r6s, fruit ; <f>vToi>,
a plant). A primary division of
plants, named from the sporocarp, or
spore-vessel, which is the result of
fertilization. Ca'r-po-phyte is the
English equivalent.

Car-y-o'p sis (*apvoi>, a nut ; 6i//is, an

appearance). A grain ; the seed-like

fruit of grasses.
Cau'-li-cle (cauliculus, a small stem).

The initial stem in an embryo.
Cell (cella, a cell). The anatomical

unit of plant-structure.
Ce'llu-lose (cellulosus, pertai7iing to

a cell). The primary substance of the
cell-wall.
Chaff. Small dry scales.

Cha-la'-za (xaA<x£a, that which is let

loose). The part of an ovule where in-
teguments and nucellus are confluent.

Chlo'-ro-phyll (xAcopos, greenish-yel-
low ; <f)vA\ov, a leaf). The green
coloring matter of plants.

Cho'r-i-sis (xcipto-is, a separating).
Longitudinal separation into two or
more similar parts.

Ci'1-i-um, pi. cilia (cilium, an eye-
lash). Marginal hairs ; motile proto-
plasmic filaments, as those of anthero-
zoids.

Closed bundle, A fibro-vascular
bundle containing no cambium.

Col-la t-er-al (con, together ; latus, a

side). Side by side ; used of a fibro-
vascular bundle in which the xylem

and phloem are side by side in a radial

direction.

Col-u-meT-la (columella, a small
column). The persistent axis of cer-
tain spore-cases, as in mosses.

Coii-ce'n-tric (con, together; centrum,
the center). Technically used of a
fibro-vascular bundle whose tissues
are arranged concentrically.

Co ni' di-o-pliore (conidia; </>e'paj, /
carry). The stalk upon which co-
nidia are borne.

Co-ni'-di-um (gonidium), pi. conidia

(yovrii offspring ; eiSos, form). The

asexual spores of certain groups.
Con ju-ga' tion (conjugatus, joined

together, paired). The sexual union

of similar cells, as in zygophytes.
Con-ne'ct ive (connecto, / connect}.

The portion of the stamen connecting

the thecae.
Co-ro'1-la (corolla, a small crown).

The inner envelope of a flower.

within the calyx, and composed of

petals.
Cor-pu's-cu-lum, pi. corpuscula

(corpusculum, a little body). The
archegonium-like structures in the
ovule of gymnosperms.
Co'r-tex (cortex, the bark). The rind
or bark.

Cortical. Relating to the cortex or

bajjk.
Cot-y-le'-don (K0Tv\r)8u>v, a cup-shaped
cavity). A primary embryo-leaf
borne by the caulicle.

GLOSSAK V.

245

Cu'pule (cupula, a little tub). The
gemma-cup of liverworts.

Cu' tide (cuticula, the skin). The
outermost film or pellicle of the epi-
dermis, differing chemically from the
remainder of the cell-wall.

Der ma'-to-gen (Se'pfia, skin; ycvvano,
I produce). The layer of nascent
epidermis in the meristem of growing
points.

I>i cho't o inous(Sixai iH two ; Tc/utyw,
/ cut). Forking regularly by pairs.

Dicotyledonous (615, double ;
cotyledon). Having two cotyledons,
or seed-leaves.

I>i oe'-cious (Sis, double ; 01*09, a
house). Having the two sex-organs
borne by distinct individuals.

K'l-a ter (^Aanjp, one that expels).
Spirally thickened cells within the
sporogonia of some liverworts, which
assist in expelling the spores.

K'm hry-oieuPpvov. fcetus, or embryo).
The young plantlet within the seed.

Embryo-sae. The cavity, within the
nucellus, in which the embryo de-
velops.

Kn-do-de'rm Is (ivhov^ within; iepfxa^
the skin). The layer of cells inclosing
the fibro-vascular bundle ; the bundle
sheath.

En dog e nous (tvSov, within;
yewdu), I produce). Originating from
internal tissues, and penetrating the
outer ones.

E'n do sperm (ivhov, within ; antpfjLa,
the seed). A parenchymatous tissue
developed within the embryo-sac.

E'n-do-spore (epoW, within; spore).
The inner layer of a spore-wall.

En-do-the'-ci-um (citSov, within ;
theca). The inner wall of the theca.

Ep-i-de'rm-is (cw, upon; Sep/uta, the
skin). The outermost layer of special
cells covering plant-surfaces.

E'p-i-phragm (c*4, upon; <£pay/bia, a

protection). In mosses, a membrane
covering the orifice of the capsule.

Ex Og-e nous <*£<*>, outside ; ytii'du*. I

produce). Originating from outer

layers of tissue.
Exo spore («{w, outsidex spore).

The outer layer of a spore-wall.
Ex tine (exter, on the outside). The

outer coat of a pollen-spore.

Fi'-ber (fibra, a Jiber). A long and
slender, thick-walled cell.

Fi'-brous. Composed of fibers.

Fi bro-va's cular (fibra, a fiber;
vasculum, a small vessel). Composed
of fibers and vessels ; fibro- vascular
bundles are the strands which make
up the framework of the higher
plants.

Filament (filum, a thread). The
stalk of the stamen, supporting the
anther ; also the individual threads of
algae or fungi.

Flowering glume In grasses, the
bract which subtends each flower,
sometimes called lower palet.

Frond (frons, a leaf). A name given
to the leaves of ferns.

Fundamental tissue. That outside
the fibro-vascular bundles and in-
closed by the epidermis, but not in-
cluded in either.

Fu-ni'c-u-lus (funiculus, a slender
rope). The stalk of an ovule or seed.

Gem' ma, pi. gemmae (gemma, a
bud). In bryophytes, many-celled
bodies for asexual propagation.

ijrlau -cous (yAavKOs, pale green* gray).

Whitened with a bloom, like that on

a cabbage-leaf.
Glume (gluma, a husk). A chaff-like

bract belonging to the inflorescence

of grasses ; the outer glumes subtend

the spikelet ; the flowering glume is

the bract of the flower.
Glu'ten (gluten, glue). A general

term for the glue-like products of

plants, especially of seeds.
Grain. A seed-like fruit, like those of

grasses, with pericarp adnate to the

seed ; also any small rounded body,

as of starch or chlorophyll.
Growing point (punctum vegeta-

246

GLOSSARY.

tionis). The group of meristem cells
at the growing tip of an organ, from
which the various tissues arise.
Gy-nce'-ci-uiii (ywrj1 a female ; 01*09,
a house). The pistil, or collective
pistils, of a flower.

Haus-to'-ri-a (haustor, a drinker).
The absorbing organs of certain para-
sitic plants.

Her ma'pli-ro-dite (ep/ma<f>p68i.T09, one
who is both male and female). Hav-
ing both kinds of sexual organs borne
together on the same axis.

Host* The plant upon which parasitic

plants [or organisms] develop, and

from which they derive their nourish-
ment.

Hy-gro-sco'p-ic (irypo9, wet; <r#eofrew,

/ look out for\. Having an avidity
for water.

Hyme'ni-um (vixrjv^ a membrane).
In fungi, a surface layer of vertical
filaments containing or bearingspores.

Hy'-pha, pi. hyphae (£</»?, a web).
The slender vegetative filaments of
fungi which may or may not be
woven into a mat (mycelium), or a

In'-tine (inter, on the inside^. The in
ner coat of a pollen-spore.

plant body.
Hy-po-de'r-ma (vno. under; Sep/uta,

the skin). The thick-walled tissues

beneath the epidermis, which serve

to strengthen it, but do not belong

to the fibro-vascular bundle.

In-ou'm-bent (incumbo, I lean upon).
Leaning or resting upon ; of cotyle-
dons, when the radicle is against the
back of one ; of anthers, when they lie
against the inner face of the filament.

In-du'-si-um, pi. indusia (indusium,
clothing). In ferns, a cellular out-
growth of the leaf covering the clus-
ters of sporangia (sori).

In-flor e's-cence (infloresco, / blos-
som). The arrangement of flowers ;
or the flowering portion of a plant.

In ter-ce'1-lu-lar. Between or among
the cells.

ln'-ter-node (inter, between ; nodus, a
joint). The part of a stem between
two nodes.

La'm-i-na (lamina, a layer). The
blade, or expanded part, of a leaf.

Leaf-trace. The fibro-vascular bun-
dles from the leaf which descend into
the stem, and sooner or later become
blended with its fibro-vascular system.

Li'g-ule (ligula, a small tongue). In
grasses, a thin appendage at the junc-
tion of leaf-blade and sheath.

Lo'd-i-cule (lodicula, a small cover-
let). A small scale in the flower of
grasses.

Macro-spore (/xa/cpo9, large ; spore).
The larger spore of the two kinds
produced by certain pteridophytes.

Me'd-ul-la-ry (medulla, /it A). Re-
lating to the pith ; medullary rays are
the pith-rays which pass outward
to the bark between the fibro-vascular
bundl

Meristem (Mcpt$w, / divide). Tis-
sues in a nascent or differentiating
state.

Me's o phyll (/ueo-o?, middle ; <f>v\\ov.
a leaf). The green or soft tissue of
a leaf, supported by the framework
and exclusive of the epidermis, called
by the older botanists parenchyma.

Mi'-cro-pyle (/mucpefc, small ; irv\r)% a
gate). The opening left by the in-
teguments of the ovule, and which
leads to the nucellus.

Mi'-cro-spore (fiucpos, small ; spore).
The smaller spore of the two kinds
produced by certain pteridophytes.

Mid rib. The central or main rib of
a leaf or thallus.

Mon-o-po'-di-al (/u.61'09, single ; irov9,
a foot). Said of a stem consisting of
a single and continuous axis (foot-
stalk).

My-ce'-li-um (/01VK779, a mushroom;
A19, cloth). The filamentous vegeta-
tive growth of fungi, composed of
hyphae.

Naked. Wanting some usual cover-
ing.

GL OSS A R V.

247

Ncf c-ta ry (nectarium, a depository for
nectar). The place or appendage in
which nectar is secreted.

Nerve (nervus, a nerve). A simple

vein or rib.

Node (nodus, a joint). That part of a
stem which normally bears leaves.

Nu-ce'l lus (nucella, a little kernel).
The mass of the ovule within the in-
teguments, sometimes called the nu-
cleus.

Nu-cle'-o-lus (diminutive of nucleus).
The sharply defined point often seen
in the nucleus.

Nu'-cle-us (nucleus, a kernel). The
usually roundish mass found in the
protoplasm of most active cells, and
differing from the rest of the proto-
plasm in its greater density.

O-o go'-ni-um, pi. oogonia («6i% an

*tX •' y°v*l% offspring). The female or-
gan of oophytes.

O-o'ph y-ta (<ioy, an egg; $vt6v% a
plant). A primary division of plants,
named, from the mode of reproduc-
tion, the egg-spore plants. O'-o-phyte
is the English equivalent.

O'-o sphere (<aov% an egg; a<£>aipa, a

sphere). The naked female egg-cell;
the mass of protoplasm prepared for
fertilization.

O'-o-spore (<ioi>, an egg; spore). In
general, the egg-cell after fertilization,
and surrounded by a cell-wall ; also
specially applied tc the spore formed
fn an oogonium.

Open bundle. A tibro- vascular bun-
dle which contains cambium.

O pe'r-cu-luin, pi. opercula (oper-
culum, a cover). In mosses, the ter-
minal lid of the capsule.

O'-va-ry (ovarius, an egg-keeper). That
part of the pistil which contains the
ovules,

O'-vule (diminutive of ovum, an egg).
The body which becomes a seed after
fertilization.

Pa -let (palea, chaff). In grasses, the
inner bract of the flower.

Pa'l 1 sade cells. The elongated

parenchyma cells of a leaf, which
stand at right angles to its surface,
and are usually confined to the upper
part.

Pal-mate (palma, the hand). Radiat-
ing like the fingers; said of the veins
or divisions of some leaves.

Pa'11-i-cle (panicula, a tuft). A loose
and irregularly branching flower-
cluster, as in many grasses.

Para' ph-y-sis,

Pi.

paraphygea

(irapa, beside ; </>vais, nature). Sterile
bodies, usually hairs, which are found
mingled with the reproductive organs
of various cryptogams.
Pa-re'n chyina (irapcyxe'co, I pour in

beside). Ordinary or typical cellular
tissue, *.*. of thin-walled, nearly iso-

diametric cells.

Par the no gen e sin (TraptfcVot, a
virgin; yeyeo-is, generation). Com-
monly applied to the production of
seed without fertilization ; but, strict-
ly, the formation of a sexual spore
without fertilization.

Pe'd-1-cel (pediculus, a little foot).
The stalk upon which an organ is
borne.

Pe-du'n-cle (pedunculus, a little foot).
The general flower-stalk.

Pe'r-i-anth (irepc, around ; ar0e?, a

flower). The floral envelopes, or
leaves of a flower, taken collectively ;
and an analogous envelope of the
sporogonia of certain liverworts.
Pe'r-i-blem (irept'0Atyia, a covering).
A name given to that part of the mer-
istem at the growing point of the
plant-axis, which lies just beneath the
epidermis and develops into the cor-
tex.

Per-i-ca'm-bi-um (wept, around;
cambium). In roots, the external
layer of the fibro-vascular cylin-
der.

Per-i-chae'-ti-um, pi. perichaetia

(irepi, around ; \airrj% hair% or leaf).

In bryophytes, the leaves or leaf-like
parts which envelop the clusters of
sex-organs, forming in some cases the
so-called flower.

248

GLOSSARY.

Pe'r-i-stom© (trept, around ; vtoilol, a
mouth). In mosses, usually bristle-
like or tooth-like structures surround-
ing the orifice of the capsule.

Per-i the'-ci-um, pi. perithecia

(ire/H, around; 0rjK>7, a case). The

spore-vessel of certain carpophytes,
containing the spore-sacs (asci).
Pe't-al {iriraKov^ a leaf). A corolla
leaf.
't-i-ole (petiolus, a little foot). The

stalk of a leaf.
Phan-e-ro-ga'-mi-a (^avepo?, evident ;

ya/uos, marriage). A primary division
(the highest) of plants, named from
their mode of reproduction, the seed-
producing plants. Pha1 'n-e-ro-gam is
the English equivalent.

Phlo'-em (</)Aoio5, the inner bark).
The bark or bast portion of a fibro-
vascular bundle.

Phy-co-cy'-an-ine (</>v/cos, sea-weed ;
Kvavos^ aark blue). A bluish coloring
matter extracted by water from cer-
tain algae.

Phy'1-lo-tax-y (</>vAAoi>, a leaf ; Ta£is,
arrangement). Leaf-arrangement.

Pi'n-na, pi. pinnae (pinna, a feather).
One of the primary divisions of a
pinnate leaf, as in ferns.

Pi'n-iiule (pinnula, a little feather).
One of the divisions of a pinna.

Pi 8-til (pistillum, a pestle). The fe-
male organ in phanerogams.

Pit. A thin place, or pit-like depres-
sion, left in the thickening of a cell-
wall.

Pla-ce'n ta, pi. placentae (placenta,

a cake). That portion of the ovary

which bears the ovules.
Ple'-rome (7rArjp<o/xa, that which fills).

A name given to that part of the mer-
istem near the growing points of the
plant-axis, which forms a central shaft
or cylinder and develops into the
axial tisj

PoT len (pollen, fine flour). The
spores developed in the anther.

Pol-lin-a'-tion. The transfer of pol-
len to its stigma.

Pro-embryo (pro, before; embryo).
In phanerogams, the chain of cells
(suspensor) formed after fertilization,
and from the lower end of which the

embryo develops.
Pro-thaT-li inn, pi. prothallia(pro,

before ; thallus, a young shoot). In

pieridophytes, the small usually
short-lived plant which develops from
the spore, and bears the sex-organs.
Pro-tone -ma, pi. protone'mata

(7rpd)T09, first ; r)ju.a, that which is sent

out). In mosses, the filamentous
growth which is produced by the
spores, and from which the leafy
moss plant is developed.

Pro-to'pli-y-ta (7rpcoTos, the first;
<1>vt6v, a plant). A primary division
of plants, named from the fact that
they include the lowest known plants.
Pro'-to-phyte is the English equivalent

Pro'-to plasm (7rpd>Tos, first ; n\d<rfiay
that which has been formed). That

substance in living cells, of varying

consistency, which is the seat of all

vital phenomena.

Pte'r-i-doid (nTtpiq, a fern; clfio?,

form). Fern like.
Pter-i-do'pli-y-ta (fl-repis, a fern;

</>vt6i', a plant). A primary division
of plants, named from its principal
group, the ferns. Pte-ri' d-o-phyte is
the English equivalent.
Py'r-e noid (nvpriu^ kernel ; eiSos.
form). Minute colorless bodies im-
bedded in the chlorophyll structures
of some lower plants.

Plu'-mule (plumula, a small^ soft
feather). The terminal bud of the
embryo above the cotyledons.

Pod. A dry, several-seeded, dehiscent
fruit; or a similar spore-case.

lla'pli-i-des (pcu/u's, a needle; cZSos,
form). Needle-like plant-crystals.

Re-ce'p ta-cle (receptaculum, a recep-
tacle). That portion of an axis or
pedicel (usually broadened) which
forms a common support for a cluster
of organs, in most cases sex-organs.

Re-ti'c-u-la-ted (reticulatus, net-like).

Having a net-like appearance.

GLOSSAR Y.

249

Kha'-chig (pix**, the backbone). The
axis of a compound leaf, or of a spike.

Rha'-phe (pa<^, a seam). In an anat-
ropous ovule, the ridge which con-
nects the chalaza with the hilum.

Khi zoiri (pi£a, a root ; €tSos, form).

Root-like ; a name applied to the root-
like hairs found in bryophytes and
pteridophytes.

Rhi'-zo-tax-y (pt£a, a root: Tafi?, ar-
rangement). Root-arrangement.

Root stock. A horizontal, more or
less thickened, root like stem, either
on the ground or underground.

Scalar i-form (scalaria, a ladder;
forma, form). A name applied to
ducts with pits horizontally elongated
and so placed that the intervening
thickening ridges appear like the
rounds of a ladder.

Scale (scala, a flight of steps). Any
thin scarious body, as a degenerated

leaf, or flat trichome.

Scle-re'n chy-ma ((tkAtjpos, hard;
iy\vfxa, an infusion). A tissue be-
longing to the fundamental system
and composed of cells that are thick-
walled, often excessively so.

Sen te'1-luin (scutella, a small disk)-
The disk-like or shield-like cotyledon
of grasses.

Seed. The fertilized and matured
ovule.

Se'p al (from the modernized word
trevaAoi', a sepal). A calyx leaf.

Se'-ta, pi. setae (seta, a bristle). A
bristle, or bristle-shaped body ; in
mosses, the stalk of the capsule.

Sheath. A thin enveloping part, as of
a filament, leaf, or resin-duct.

Sieve-cells. Cells belonging to the
phloem, and characterized by the pres-
ence of circumscribed and perforated
panels in the walls ; the panels are
sieve-plates^ and the perforations
sieve-pores.

So'-rus, pi. sorl (cnopds, a heap). In

ferns, the groups of sporangia, con-
stituting the so-called " fruit-dots ; "
in parasitic fungi, well-defined groups

of spores, breaking through the epi-
dermis of the host.

Spike (spica, an ear of corn). A flower-
cluster, having its flowers sessile on
an elongated axis.

Spi ke let (diminutive of spike). A
secondary spike ; in grasses, the ulti-
mate flower-cluster, consisting of one
or more flowers subtended by a com-
mon pair of glumes.

Spo-ra'n-gi-um, pi. sporangia
(spore ; ayyos, a vessel). The spore-
vessel ; applied to ferns and certain
lower groups.

Spore (<rwop<i, seed). Originally used
as the analogue of seed in flowerless
plants ; now applied to any one-celled
or few-celled body which is separated
from the parent for the purpose of
reproduction, whether sexually or
asexually produced ; the different
methods of its production are indi-
cated by suitable prefixes.

Spo-ro go' ni um, pi. sporogonia
(spore ; yoyi}, offspring). The whole

structure of the spore-bearing stage
of bryophytes.

Sta'-men <<mjfAu>*', the warp or thread
of cloth). The male organ in phane-
rogams.

Sti'g-ma (arty/ma, a spot^ or mark).
The surface of a pistil without epi-
dermis which receives the pollen.

Stig-ma't ic. Relating to the stigma,
or stigma-like.

Sto'-ma, pi. sto'mata (<rr6fxa, a
month). Epidermal structures which
serve for facilitating gaseous inter-
changes with the external air, often
called " breathing-pores."

Stro'-phi-ole (strophiolum, a small
wreath). An appendage at the hilum
of certain seeds.

Style (otOAos, a pillar). The usually
attenuated portion of the pistil which
bears the stigma.

Sus-pe'n-sor (suspendo, / hang). See
Pro-embryo.

Syn-e'r-gi dae, or Synergides

(avvepyeu), I work together). The two

nucleated bodies which accompany

2$0

GLOSSARY.

the oosphere in the embryo-sac, and
together with it form the egg-appara-
tus.

Te's-ta (testa, a shell). The outer

seed-coat.
Tet-rady'n a-mous (rtTpas, four ;

SuVa/xi?, strength). Said of an androe-

cium in which there are four long and

two shorter stamens.
Tha'1-loid (thallus ; ciSos, form).

Thallus-like.
Tha'1-lus (0aAA6s, a young shoot).

The body of lower plants, which ex-
hibits no differentiation of stem, leaf,

and root.
The' ca, pi. thecae (OrJKrj, a case). The

44 anther-cell," that is, the case con-
taining pollen ; sometimes used of
other spore-cases.
Tra'cheary tissue. A general name

given to the vessels and ducts found
in fibro vascular bundles.

Tra'-che-ides (Tpaxvs, rough ; elSos,

form). Tracheary cells that are closed
throughout.
Tri'-chome (0pt£, hair). A general
name for a slender outgrowth from
the epidermis, usually arising from a
single cell.

Turgid i-ty (turgidus, swollen). The
normal swollen condition of cells
which results from the avidity of pro-
toplasm for water.

Vein (vena, a vein). The fibro-vascu-
lar bundle of leaves or any flat organ.

Ve na'-tion (vena, a vein). The mode

of vein distribution.

Xy'-lem (fvAoi>, wood). The wood
(inner) portion of the fibro-vascular
bundle.

Zo'-o-spore (£«&oi% an animal ; spore).

A free-moving spore.
Zy-go-mo'r-phic (&y6v, a yoke:

/utop<£>7, form). Said of a flower which
can be bisected by only one plane into
similar halves.

Zy-go'ph-y-ta (ivyov, a yoke ; <f>vTov, a
plant). A primary division of plants,
named from their mode of reproduc-
tion, the sexual spore being produced
by conjugation. Zy'-go-phyte is the
English equivalent.

Zy'-go-spore (£vydp, a yoke; spore).
The spore of zygophytes, formed by
conjugation.

•

N DEX.

Numbers in light type refer to the laboratory part, those in heavy

type to other parts of the book.

Alternation of generations, 100

Adiantum, means of recognizing,
103; gross anatomy, 105; mi-
nute anatomy, in; annotations,
124

Anatropous ovule, 214, 217

Androecium, 202

Annual rings, 162

Annulus, no, 120

Anther, 178, 189, 203, 226

Antheridia, 47, 48, 55, 63, 72, 82,
88, 93, 122, 128, 168

Antherozoids, 63, 72, 82, 93, 100,
122, 128, 169

Anthotaxy, 176

Antipodal cells, 241

Apical cell, 118

Apophysis, 89, 96

Appendages of perithecia, 54, 57

Archegonia, 75, 77, 82, 88, 94,123,
129, 161, 168

Areolae, 60
Asci, 54
Ascospores, 54

Atrichum, how to recognize, 84;
gross anatomy, 86; minute

discovery of the sexual organs,
99; nature of the fruit, 100
Avena, gross anatomy, 172; mi
nute anatomy, i8o;annotations,

192; homology of the flower, 193
Awn, 177

Axis of inflorescence, 176

Bark, 136

Bast parenchyma, 209
Blade of leaf, 175

Books of reference, 20
Bordered pits, 144, 147, 164
Bracts, 139, 162, 193, 237
Branches, arrangement of, 133
Bulliform cells, 195
Bundle sheath, m, 113, 126, 153,

155, 181, 184, 206, 219, 229,

231, 240

Callus-plate, 165

Calyptra, 86, 89, 97, 101
Calyx, 202

Cambium, 142, 144, 147, 164, 239
Camel's-hair brush, how mount-
ed, 3

anatomy, 90; annotations, 97; Camera lucida, use of, 19

INDEX.

Campylotropous seed, 227
Canal of archegonia, 77, 94, 123,

129

Capsella, how to recognize, 222;
gross anatomy, 223; minute
anatomy, 228; annotations, 236

Capsule, 86, 89, 95, 101

Carpellary scale, 139, 140, 159,
163

Carpels, 163, 202, 204, 213, 217

Carpogonium, 55
Carpophyll, 163
Carpophyta, 48, 55

Caryopsis, 179

Caulicle, 141, 180, 192, 228, 236

Cell, 25; division of the, 26

Cell-sap, 40

Cellulose, 26

Cell-wall, 24, 26

Chaff of moss, 88; of oats, 179

Chalaza, 205
Chlor-iodide of zinc, 5
Chlorophyll, test for, 23, 29, 31;

nature of, 25; bands, 36, 40;

bodies, 24, 77, 119 ; grains, 67,

77
Cilia, 26, 47, 73* 83, 94, 100, 123
Closed bundle, 195, 209, 220
Collateral bundle, 165, 195, 240
Columella, 90, 95
Concentric bundle, 114, 126
Conducting tissue of style, 221,

241

Cones, 140, 159

Conidia, 44, 45, 50, 53, 56

Conidiophores, 45, 46, 53
Conjugating filaments, 35; tubes,

Connective of anther, 189, 203,

212
Conocephalus, 59, 61

Continuity of protoplasm, 127

Cork, 229

Corolla, 202

Corpuscula, 161

Cotyledons, 141, 180, 228, 236

Cover-glasses, cleaning, 11; kind

to use, 3; receptacle for, 11
Cupules, 60, 62, 68
Cuticle, 112, 146, 152, 183
Cystopus, where found, 43; gross
anatomy, 44; minute anatomy,
45; annotations, 48; mode of
life, 49; means of distribution^.
49; nature of its parasitism, 50

Dark-green scum, 28

Definitive nucleus, 241
Dermatogen, 182, 206
Dichotomous branching, 60, 79
Dicotyledons, characters of, 236
Dispersion of offspring, 50, 170
Drawing, importance of, 16; kinds

of, 17, 18; suitable materials

for, 4

Elaters, 65, 76, 83

Embryo, 141, 170, 179, 192, 205,

215, 228, 235
Embryonal vesicle, 241
Embryo-sac, 140, 160, 169, 214,

235, 241
Empty glume, 176

Endogenous origin of roots, 192.

208, 220

Endosperm, 140, 141, 160, 169,

178, 241
Endospore, 121
Endothecium, 189, 213, 234
Epidermis, 66, 91, 112, 118, 152,

154, 157,181, 183, 186,188,211,

230

INDEX.

253

£piphragm, 89, 96, 101
Exogenous growth, 208, 220

Exospore, 121

Extine> 158, ixjp. 213, 234

Fertilization, mode of contact

in, 169; in Pinus, 170
Fertilizing-tube, 48, 49, 51, 169

Fibrous tissue, 120

Fibro- vascular bundle, 113, 125.

153, 166, 181, 184, 209, 229, 230
Filament of stamen, 178, 203, 212,

226? 233
Flowering glume, 177, 193
Flower, character of a true, 216;

in Pinus, 162; nature of, in oats,

193
Forceps, 3
Frond, 105
Funiculus, 205, 214, 227

Gemm/E, 60, 62, 70, 80

Germination of conidia, 56; of

moss spores, 102
Glume, 176, 177, 188, 193
Gluten-containing cells, 191
Glycerine, 6, 13
Grain of oats, 179, 195
Green slime, 22
Growing-point, 151, 182, 195, 200,

208, 219
Growth rings, 135, 142, 162, 165
Guard-cells, 66, 118, 152,166, 183,

186
Gynoecium, 202

Hairs of thallus, 60, 6i, 78; of
cupule, 69; of fruit, 179

Haustoria, 46, 49, 53, 56

Head of liverwort, 63, 64, 81; of
moss, 86, 87, 93

Hermaphrodite flower, 194

Hygroscopic cells, 176, 187, 195

Hymenium, 45

Hyphae, 46

Hypoderma, 152, 154, 183

Indusium, no

Instruments for laboratory, 1

Integument of ovule, 139, 159,

163, 235
Intercellular spaces, 127, 185, 209
Internodes, 105, 174, 199
Intine, 158, 170, 190, 213, 234
Iodine, 5

Keel of carpellary scale, 139, 164

Lamina, 87, 92

Leaf-trace, 91, 99, 219

Leaves of Marchantia, 61, 68, 79;

of Atrichum, 87, 92 98; of

Adiantum 107, 118; of Pinus,

137, 151, 162; of Avena, 175; of

Trillium, 220; of Capsella, 225

Ligule, 175, 193
Lilac mildew, 52

Liverwort, 58
Lodicules, 177, 193
Lunularia, 59

Macrospores, 168, 241

Magenta, 5

Magnifying power of micro-
scope, 18

Maiden-hair fern, 104

Marchantia, how to recognize,
58; gross anatomy, 59; minute
anatomy 66; annotations, 77

Material, care and use of, 15

Medullary rays, 135, 142, 145, 240

Meristem, 151, 206, 228

254

INDEX.

Mesophyll, 109, 119, 138, 153,
155, 166, 175, 187, 210, 232

Microscope, use of, 6; fine ad-
justment, 16; high and low pow-
ers, 3; to determine magnifying
power, 18

Microsphaera, how to recognize,
52; gross anatomy, 52; minute
anatomy, 53; annotations, 55

Microspores, 168, 240

Micropyle, 139, 140, 159

Middle lamella, 112, 127, 144, 207

Midrib of thallus, 60; of leaf, 87,
92, 99

Moss, 84

Mounting, 11

Movements of Oscillaria, 32

Mycelium, 45, 53

Ovary, 178, 195, 203, 214. 221,

234, 238
Ovules, 139, 140, 162, 178, 194,
204, 214, 217, 235

Naked ovule in Pinus, 163

Nectaries, 226

Needles for dissecting, 2

Nerves, 176

Nodes, 105, 174, 192, 199

Nucellus, 140, 159, 214

Nucleolus, 24, 38

Nucleus, 24, 25, 37; of starch, 112

Nutritive solution, 34

Oats, 172

Oogonia, 47, 48

Oophyta, 48

Oosphere, 47, 77, 83, 94, 100,

124, 129, 170, 241
Oospore, 44, 48, 49, 235, 242
Open bundle, 240
Operculum, 89, 96
Oscillaria, occurrence of, 28;

gross and minute anatomy, 29;

annotations, 31; movements of,

Palet, 177, 188, 193

Palisade parenchyma, 187, 210,
232

Panicle, 176

Paraphyses, 72, 75, 82, 88, 93

Parenchyma, 67, 70, 113, 142,

143, 145, 153, 183, 187, 209
Parthenogenesis, 51, 55

Pedicel of receptacle, 60, 62, 70,
73, 81; of gemma, 70; of flower.
223, 237; of conidia, 45; of
archegonia, 94; of asci, 54; of
antheridia, 72, 93

Peduncle, 139

Pencils for drawing, 4

Pens for drawing, 4

Perianth, 65, 76, 194, 216

Periblem, 182, 206

Pericambium, 117, 126, 207

Perichaetium, 64, 75, 82

Peristome, 89, 96

Perithecia, 53, 54

Petals, 202, 212, 226, 233, 238

Petiole, 201

Phloem, 1x3, 142, 144, 153, 209

Phycocyanine, 29, 31

Phyllotaxy, 225

Pinnae, 108

Pinnules, 107, 108

Pistil, 178, 227, 234

Pith, 135, 142, 231; for section

cutting, 10
Pits in cell-wall, 112, 127, 144,

147, 152
Placentae, 204, 217

Plerome, 1S2, 206

INDEX.

255

Plumule, 141, 180, 192

Pod, 205

Pollen, 138, 158, 169, 178, 189,

190, 194, 203, 213, 227, 234
Pollen sac, 138, 157, 194
Pollen tube, 169, 235, 241
Pollination in Pinus, 164
Polytrichum, 85
Pond scum, 33
Potassic chlorate, 6; hydrate, 5,

Primary meristem, 151, 206
Primordial utricle, 40
Pro embryo, 235, 242
Prothaliia, 104, Hi, 121, 128,

168, 194, 241
Protococcus, distribution of, 22;

gross and minute anatomy, 23;

annotations, 25
Protonema, 86, 90, 102
Protoplasm, test for, 24, 25; in

the cell, 40; in pollen, 158
Pteridoid stage, 128
Punctum vegetationis, 219
Pyrenoid, 37, 40

Radial bundle, 117, 126, 195, 218

Radish flowers, 43

Raphides, 201, 233

Razor, kind to use, 2; care of, 9

Reagents, 4; use of, 13

Receptacle, 60, 64, 71, 74, 87,

202, 226
Reference books, 19
Resin ducts, 135, 143, 145, 148

153, 155, 167
Resting spores, 42, 49, 56
Rhachis of leaf, 107; of spikelet,

J77

Rhaphe, 205

Rhizoids, 61, 79, 86, 90, ill, 122

Rhizome, 105

Rhizotaxy, 223

Roots/* 79, 105, 116, 124, 173,

219, 238
Root cap, 107, 118, 124, 174, 182,

205, 238
Root-hairs, 97, 107, 118, 174, 206
Root-sheath, 180, 192
Root-stock, 198, 199, 207, 218

Scalariform vessels, 1:3, j 14,

"7
Scale leaves of Atrichum, 87; of

Pinus, 132, 137, 146, I49>16^;
of Trillium, 200, 201, 218
Scales (trichomes) on rhizome,
105, 107, 116; on thallus, 60,

62, 79
Sclerenchyma, in, 115

Scotch pine, 130

Scutellum, 180, 192

Section cutting, 8

Seed, 141, 170. 205, 215, 227, 236

Selaginella, 168

Sepals, 202, 211, 226, 233

Seta, 86, 89, 95, 100

Sexuality, simplest form of, 42;
significance of, 51

Sexual process, 41

Sheath of filament, 30, 31, 36, 39;
of leaf, 175, 188; of resin duct,
143; of root, 180. 192; of root-
stock, 208, 220; of bundle — see

Bundle sheath

ShepherdVpurse, 222

Sieve cells, 113, 115, 144, 148,

165; plates, 115, 126, 145, 165;

tissue, 207, 209
Sori, 44, no
Sperm-cell, 122
Spike, 139

256

INDEX.

Spikelet, 176

Spiral vessels, 143, 225

Spirogyra, occurrence of? 33; to
grow, 34; gross anatomy, 34;
minute anatomy, 35; annota-
tions, 39

Spongy parenchyma, 210, 221,
232

Sporangia, no, 120

Sporogonia, 64, 76, 83, 86, no,
120

Staining, 13

Stamens, 132, 138, 157, 162, 178,
194, 202, 212, 226, 233, 238

Starch, 37, 40, 112, 158

Stigmas, 178, 190, 194, 204, 217,

234

Stigmatic cells, 77, 83, 94; sur-
faces, 213

Stomata, 61, 66, 68, 71, 78, 101,
119, 127, 138, 152, 188

Strophiole, 205, 215

Styles, 178, 190, 204, 217

Subterranean stem, 199

Sulphuric acid, 6, 13

Supplementary guard-cells, 66

Suspensor, 242

Synergidae, 241

Tap root, 237

~7 _

Teeth of the peristome, 97, 101
Testa, 205, 215, 236

Tetradynamous stamens, 237
Thalloid stem, 77, 128
Thallus, 59, 66, 77
Thecae of anther, 189, 203, 2J2,

234
Tillering point, 173

Tracheides, 143, 147, 164, 167, 182
Transfusion tissue, 167
Trichomes, 61, 66, 75, 10^, 120,
122, 125, 173, 191

Trillium, description of, 197;
gross anatomy, 198; minute
anatomy, 205; annotations, 215

Turgidity of cells, 30, 32, 38

Veins, 109, 201, 211

Venation, 109, 218
Vesicle of antherozoid, 73, 83, 94,
123

White rust, 43

Wings of thallus, 60; of pollen,

158
Wood, 135, 142, 164; cells, 143;

parenchyma, 209

Xylem, 113, 142, 143, 147, 153,
209

Zoospores, 26, 47, 50

Zygophyta, 48
Zygospores, 35, 39, 42

THE AMERICAN SCIENCE

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same

monstratim? to the class the f

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&** *~ "*w ---~~ &

of a few typical forms, then taught to compare these with
others, and finally led to the principles or inductions growing
out of the facts.

From A. E. Verrill, Professor of Zoology in Yale College : " The
general treatment of the subject is good, and the descriptions of
structure and the definitions of groups are, for the most part, clear,
concise, and not so much overburdened by technical terms as in sev-
eral other manuals of structural zoology now in use."

Briefer Course. i2mo. Pp. 334. $1.40.

The distinctive characteristic of this book is its use of the

■

object method. The author would have the pupils first examine
and roughly dissect a fish, in order to attain some notion of
vertebrate structure as a basis of comparison. Beginning then
with the lowest forms, he leads the pupil through the whole
animal kingdom until man is reached. As each of its great
divisions comes under observation, he gives detailed instruc-
tions for dissecting some one animal as a type of the class, and
bases the study of other forms on the knowledge thus obtained.

From Herbert Osborn, Professor of Zoology, lotva Agricultural
College : " I can gladly recommend it to any one desiring a work of
such character. While I strongly insist that students should study
animals from the animals themselves, — a point strongly urged by
Prof. Packard in his preface, — I also recognize the necessity of a
reliable text-book as a guide. As such a guide, and covering the
ground it does, I know of nothing better than Packard's."

From D. M. FiSK, Professor of ATatural History, Hillsdale College ;
" The ' Briefer Courses ' of Packard and Martin have been adopted,
and for these reasons : 1. They are brief ; the lessened mechanical
labor of mastering a text leaves time for more observation and for
comparison of authorities. 2. They are clear ; the work of cutting
away needless nomenclature has been done with skill. 3. They are
authoritative ; serious students can have confidence in even brief and
dogmatic statements, knowing they come from a master, and not from
a mere compiler. 4. They are fresh ; fossils are good in their places,
but a fossil text-book in science is a fraud on youth."

THE AMERICAN SCIENCE SERIES. 5

ZOOLOQY— Continued.

Elementary Course. {In press?)

In general method this book is the same with those just de-
scribed, but, being meant for quite young pupils, it gives more
attention to the higher organisms, and to such particulars as
can be studied with the naked eye. In everything the aim has
been to make clear the cardinal principles of animal life, rather
than to fill the pupil's mind with a mass of what may appear to
him unrelated facts.

BOTANY. By Charles E. Bessey, Professor in the Univer-
sity of Nebraska.

Advanced Course. Large 12 mo. Pp. 611. $2. 75.

Aims to lead the student to obtain at first-hand his knowl-
edge of the anatomy and physiology of plants. Accordingly,
the presentation of matter is such as to fit the book for con-
stant use in the laboratory, the text supplying the outline sketch

which the student is to nil in by the aid ot scalpel and micro-
scope.

From J. C. Arthur, Editor of The Botanical Gazette : "The first
botanical text-book issued in America which treats the most important
departments of the science with anything like due consideration.
This is especially true in reference to the physiology and histology of
plants, and also to special morphology. Structural Botany and clas-
sification have up to the present time monopolized the field, greatly
retarding the diffusion of a more complete knowledge of the science."

Briefer Course. i2mo. Pp.292. $1.35.

A guide to beginners. Its principles are, that the true aim of
botanical study is not so much to seek the family and proper
names of specimens as to ascertain the laws of plant structure
and plant life ; that this can be done only by examining and
dissecting the plants themselves; and that it is best to confine
the attention to a few leading types, and to take up first the
simpler and more easily understood forms, and afterwards those
whose structure and functions are more complex. The latest
editions of the work contain a chapter on the Gross Anatomy
of Flowering Plants.

From J. T. Rothrock, Professor in the University of Pennsylva-
nia : " There is nothing superficial in it, nothing needless introduced,
nothing essential left out. The language is lucid ; and, as the crown-
ing merit of the book, the author has introduced throughout the vol-
ume * Practical Studies,' which direct the student in his effort to see
for himself all that the text -book teaches."

6 THE AMERICAN SCIENCE SERIES,

CHEMISTRY. By Ira Remsen, Professor in the Johns Hop-

kins University,

Briefer Course. i2mo. Pp. 387. $1.40.

An introduction to the study of chemistry, following the
inductive method. To avoid overburdening the student's mind,
the author has presented a smaller number of facts than is
usual in elementary courses in chemistry, but he has at the same
time taken pains to select for treatment such substances and
such phenomena as seem best suited to give an insight into the
nature of chemical action. In other words, he has aimed to
make the book scientific, to lay stress upon the relations which
exist between the phenomena considered, and not to present
merely a mass of apparently disconnected facts. Another
feature of the work is that principles and laws are treated be-
fore the theories which are proposed to account for them.

The other books arranged for in this series are as follows :
PHYSICS. By Arthur Wright, Professor in Yale College.

{In preparation.)

GEOLOCY. By Raphael Pumpelly, late Professor in Har-
vard University. {In preparation.)

PSYCHOLOGY. By William James, Professor in Harvard
University. (In preparation?)

GOVERNMENT. By Edwin L. Godkin, Editor of the Nation*

{In preparation?)

■V

THIS B

K IS DUE ON THE LAST DATE
STAMPED BELOW

AN INITIAL FINE OF 25 CENTS

WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK
ON THE DATE DUE. THE PENALTY WILL INCREASE TO
50 CENTS ON THE FOURTH DAY AND TO $1.00 ON THE
SEVENTH DAY OVERDUE.

Book Slip~10m-8,,58(5916s4)458

Arthur, J»G.

Handbook of plant

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