X. With a sharp razor, wet with water or with very weak
spirit if the material be fresh, or with strong spirit if it has been
previously hardened in alcohol, remove the extreme apex of
the punctum vegetationis^ taking care to cut accurately in a
transverse plane : mount in water or in weak glycerine, and
examine with a low power. If the section be thin enough, it
will be seen that a large cell of triangular outline occupies
the centre of the apical cone, while the cells immediately sur-
rounding it are arranged in more regular order than those at a
greater distance. This cell is the apical cell, and the cells
surrounding it have been derived by cell-division from it, by
mean of walls parallel to its three sides : they are called the



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PTERIS-RHIZOME 167

segmental cells, and it may readily be seen that these again
undergo subdivision. If the section be not sufficiently trans-
parent, it may be treated with very dilute potash and weak gly-
cerine, or, better, with " eau de javelle, ,> which will clarify the
tissues, and make the cell-walls more distinct.

The form of the apical cell, and of the segmental cells which
surround it, will be readily appreciated on comparison of Fig. 11.



Fig. 11. — View of a model of a three-sided pyramidal (or tetrahedral) apical cell, as
seen from above ; the walls d e,f g, h k f denote successive walls by which seg-
ments have been cut oflf from the growing apical cell : i is the apex of the
pyramidal cell, at which point the three youngest segmental walls cut one another.
(After Sachs.)



XI. From the apex of another plant cut median longitudinal
sections : mount in weak glycerine : a very little dilute potash
may be added if the sections are not transparent enough, or
they may be treated first with " eau de javelle," and then be
mounted in glycerine.

If any one of the sections has passed through the apical cone,
in a median plane, the apical cell will be seen presenting a
wedge-like appearance, and the cells around it will show, in the
regularity of their arrangement, that they have been derived
from segments successively cut off from the apical cell.
(Compare Fig. 1 2.) It may be concluded from the observation
of transverse and median longitudinal sections that the form of
the apical cell is that of a three-sided pyramid.



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PRACTICAL BOTANY



The structure and mode of origin of the young leaves should
also be observed in the median longitudinal sections.



The Root.

XII. Cut transverse sections of the root of the Male Fern,
selecting for that purpose the thickest part of an old root :
mount in glycerine, and observe—

I. The piliferons layer : certain cells of this superficial layer




Fig. 12.— Diagram showing the arrangement of cell-walls as seen in a median longi-
tudinal section through an apical cone with a pyramidal apical cell. A A, are
the segmental walls, which form part of the system of anticlinals ; a, a, walls by
which each segment is cut into two equal halves : these complete the anticlinal
curves ; P P t periclinals, which are not completed up to the apex. (After Sachs.)

have grown out as root-hairs, remnants of which may still be
seen.

2. The greater part of the section consists of the bulky,
brown-walled cortex, of which the outer parts are thin-walled ;
but, passing inwards, there is a sudden increase in thickness
of the wall, so as to form a dense ■clerenchymatous ring ; this
surrounds —

3* The entoderms, which consists of a single layer of cells



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NEPHRODIUM- SPOROPHYTE 169

flattened tangentially, and having the usual dot-like marking of
the radial walls : this may be difficult to observe, as the radial
walls are often pressed out of shape. Within this layer lies —

4. The pericycle, which usually consists of two layers of cells
with thin walls, and obvious protoplasmic contents. The
vascular tissues inclosed within these layers are arranged
according to the ordinary radial type : thus there will be
seen : —

5. Two groups of xylem abutting on the pericycle and
composed of tracheides of various size, the largest being near
the centre of the root ; as the root develops, the two originally
separate groups of xylem unite at the centre by formation of
fresh tracheides, and together form a flat band which traverses
the root longitudinally. Alternating with the groups of
primary xylem at the periphery of the vascular cylinder
are —

6. Two groups of phloem, consisting mainly of sieve-tubes
having the same characters as those of the stem. Scattered
among the vascular elements are cells of conjunctive paren-
chyma.

XIII. Cut median longitudinal sections of the apex of a root
which has been hardened in alcohol : at most only one
absolutely median section can be obtained from a single root :
it will be found convenient to embed the apex of the root in
paraffin, or to hold it between pieces of pith or carrot.
Mount in glycerine, and examine first with a low power : choose
out those sections in which there is a symmetrical arrangement
of tissues around a single, large, apparently three-cornered
apical cell, which lies at some distance from the extreme apex.
(Compare Fig. 13.) Note —

1. That the orientation of the apical cell is constant, i.e. one
corner is directed towards the older part of the root, while the
side opposite that corner, i.e. the anterior face or base of the
cell, is perpendicular to the axis of the root.

2. That around the apical cell are regularly arranged seg-
mental cells, which have successively been cut off from it by
walls parallel to the sides of the apical cell. Of these—

a. Those successively cut off from the base form the root-



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170



PRACTICAL BOTANY



cap, dividing up by regularly arranged walls into a mass of
regular cells.

b. Those cut off from the sides of the apical cell form the
body of the root : these also divide by walls in regular suc-
cession. Observe carefully the arrangement of these walls, and
by comparison of several sections ascertain their order of




«•• 3Z t



Fig. 13.— Diagram illustrating the arrangement of cell-walls as seen in a median
longitudinal section through the apex of the root of a Fern. /. ///. &c. indicate
segments cut off from the sides of the apical cell, which go to form the body of
the root ; k, /, m, «, /, are successive segments from its base, which go to form
the root-cap. (After Goebel.)



succession, and their relation to the various tissues of the root
above described.

XIV. Cut successive transverse sections of the apex of a root
which has been hardened in alcohol : this may easily be done
if the root be held between pieces of pith, or better by em-
bedding in paraffin. If possible, keep all the sections in their
proper order of succession, and mount in glycerine. Examine
with a low power, and choose out those in which the large
apical cell is to be seen. Observe carefully—

1. The form of the apical cell, apparently three-sided :



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NEPHRODIUM— SPOROPH YTE 1 71

combining this result with that obtained by examination of
the longitudinal sections the form of the whole cell must be a
three-sided pyramid. (Compare Fig. II.)

2. The segments are arranged in regular order round it, and
are cut off successively from the three sides.

3. Note the mode in which the several segments are further
divided.

Next examine a section which has passed through the root-
cap immediately above the apical cell : this will include the
young segments cut off from the base of the apical cell by
transverse walls, and destined to form the root-cap. Note the
first divisions of these segments by walls arranged crosswise :
it may be seen that these walls do not coincide in position in
successive segments.

The Leaf.

XV. Cut transverse sections of a pinna of a leaf of the Male
Fern which has no sori upon it : mount in weak glycerine, and
observe with a low power that the outline of the section shows
the leaf to be of equal thickness throughout, except where
traversed by vascular bundles : at those points the pinna is
thickened, the lower surface projecting convexly.

Examine with a high power, and observe successively the
following tissues, starting from the upper surface : —

1. A regular epidermis with a, thin cuticle: the epidermal
cells contain chlorophyll : there are no stomata.

2. The mesophyll consists in its upper part of thin- walled
cells containing chlorophyll, and with small intercellular spaces ;
this passes by gradual transition into the lower part, where the
intercellular spaces are larger, and the form of the cells less
regular. Internal glandular hairs are frequently to be found in
the intercellular spaces of the mesophyll.

3. The lower epidermis, the cells of which also contain
chlorophyll : numerous stomata are present : note the form of
the two guard-cells as seen in transverse section, and their
position in relation to the epidermis.

4. Here and there vascular bundles! of circular appearance



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ijz PRACTICAL feof AKtf

in transverse section, will be found embedded in the mesophyll :
the larger of these correspond in position to the swollen ribs of
the pinna.

Note the endodermis as a continuous layer of cells, which com-
pletely surrounds the circular bundle, and within this the xylem
and phloem elements, similar to those of the stem : the bundles
show an approach to the collateral type, the xylem being
nearest to the upper surface of the leaf.

XVI. Cut tangential sections (or strip off the epidermis)
from the upper and the lower surface of the leaf: mount as
before, and compare them.

a. The epidermis of the upper surface will be found to
consist of cells with sinuous outline, and protoplasmic contents,
with chlorophyll : no stomata will be found.

b. The epidermis of the lower surface consists of cells
similar to the above : there are stomata with two guard-cells.

The Sporangia.

XVII. Having examined the sori as directed on p. 156 with
the naked eye or with a lens, cut transverse sections through
pinnae of leaves which bear sort, taking care that the sections
shall pass through one or more of them : mount as before, and
examine with a low power. Note —

1. The structure of the pinna, as above described.

2. Opposite to, and seated upon a rib will be found the
membranous indusium, which, like an umbrella, covers over —

3. The sporangia, which are biconvex-lens-shaped, brown
stalked capsules, attached to the rib and filled with —

4. Numerous roundish, brown, unicellullar spores.
Observe more closely the structure of the single sporangium.

It is composed of—

i. The stalk, which is of considerable length, and usually
consists of three rows of cells. Stalked glandular bodies are
often found as lateral branches on the stalk of the sporangium
in this species.

ii. The capsule, which has the form of a biconvex lens, and
consists of a marginal series of cells with peculiarly thickened



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NEPHRODIUM— SPOROPH YTE 1 73

walls, which constitute the ring, or annulus ; and thinner-walled,
flattened cells, which together form the lateral walls of the
completely closed sporangium.

Place a number of mature, but not yet ruptured sporangia
upon a dry slide : warm them very gently over a spirit-lamp,
and observe quickly under a low power : note the sudden
explosive rupture of the sporangia, so as to eject and scatter
the spores : this is due to the straightening of the annulus or
ring. Similar results may be obtained by mounting in water,
and subsequently adding glycerine ; in fact, on the removal of
water by evaporation into the air, or by a reagent such as gly-
cerine, the curved annulus tends to straighten itself, and then
ruptures the thin wall of the sporangium.

Note sporangia in which the thin lateral walls have been
ruptured transversely, the ring having straightened itself out :
now breathe on the sporangia, and note that on being thus
moistened by the breath the annulus becomes more curved,
while on being left exposed to the dry air for a few minutes it
again becomes straight.

Examine single spores under a high power : they are
unicellular bodies, having a brown wall, with external band-
like outgrowths of the exospore or outer layer of the wall. All
the spores are alike (Homosporous).

The various stages of development of the sporangium may
be found in any sorus in which only the first sporangia have
come to maturity : treat the sections previously with weak
potash ; if this makes them too transparent, neutralize with
weak acetic acid, and mount in glycerine ; or the sections may
be treated at once with " eau de javelle," and then be mounted
in glycerine.



B.—THE GAMETOPHYTE, OR OOPHYTE.

I. Dry some of the leaves of the Male Fern, which bear sori,
on a piece of paper : the spores will then be set free by the
rupture of the sporangia, and they may thus be collected in
large quantities. Sow some of them on damp earth : keep



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174 PRACTICAL BOTANY

them moist, and sheltered from direct sunlight ; they will then
germinate, and after a few weeks the surface of the soil will be
found to be covered with small, green, flattened bodies, each of
which is an individual prothallus.

From time to time, pick off some of the young prothalli with"
a needle from the surface of the soil : by this means a series of
observations may be made which will illustrate successive
stages of development of the prothallus.

II. Examine a single, fully-grown prothallus with the naked
eye, and observe —

1. The form, .which is flattened, and more or less kidney-
shaped, with a depression of the margin, at the base of which
is the organic apex of the prothallus. Note that the central
part of the prothallus is often perceptibly thicker than the
periphery : this thicker part is called the cushion.

2. The position of the prothallus while growing : it is usually
oblique to the surface of the soil.

3. The root-hairs, which spring from the under surface of
the cushion, and run downwards into the soil.

4. The green-colour, due to the presence of chlorophyll :
the prothallus is thus capable, under suitable circumstances, of
carrying on the process of elaboration of fresh organic sub-
stances.

III. Wash a fresh, well-developed prothallus carefully in
water, so as to remove the soil from the root-hairs : mount it
whole in water, with the lower surface directed upwards, and
examine it with a low power. Observe again the chief points
seen above with the naked eye, which are now more plainly
visible, and note especially —

1. The form and structure of the cells in the lateral, thinner
portions of the prothallus ; they are polygonal, and have thin
cellulose walls, and protoplasm containing a nucleus and
numerous chlorophyll-corpuscles : the cells at the margin are
often extended as hair-like outgrowths.

2. The cells composing the cushion are of similar structure,
but are aggregated in a mass more than one layer of cells in
thickness : many of the cells will be seen to have grown out as
root-hairs.



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NEPHRODIUM— GAMETOPHYTE . 175



3. The depressed apex of the prothallus, which is occupied,
not by a single wedge-shaped cell, as is the case in early stages
of development, but by a closely aggregated series of marginal
cells, with thin cell-walls, and every appearance of recent and,
repeated cell-divisions.

4. The antheridia, which are hemispherical outgrowths,
situated chiefly on the posterior and lateral portions of the
under side of the prothallus.

5. The archegonia, which are situated on the cushion near to
the organic apex of the prothallus ; jthe multicellular neck of the
archegoniun projects from the surface of the prothallus as an
elongated cylindrical structure.

Under the low power select one mature antheridium, and,
without moving the slide, adjust the higher power so as to
observe the structure of the same antheridium in detail. It will
then be seen that it consists of —

a. A wall, composed of a single layer of narrow cells ; this
completely surrounds —

b. The spermatocytes, or mother-cells of the spermatozoids,
which are small, and not very numerous.

Other antheridia may be found which have already burst the
outer wall : in these the contents of the mother-cells may perhaps
be seen escaping from the ruptured antheridium as spiral
apermatosoida, endowed with active movements. If a prepara-
tion showing motile spermatozoids be treated with a weak
solution of iodine, the movements will cease with the death of
the spermatozoids, which will assume a brown staining, while
the cilia attached to the anterior ends of them will then be
clearly seen.

Select under the low power one mature archea-onium, and
then observe it in detail under the higher power. If the neck
be vertical, which would under the circumstances be the natural
position, since the prothallus was mounted with the lower surface
uppermost, there will then be seen, on focusing down upon it,
four rows of cells composing the wall of the neck, and surround-
ing one cell, the canal-cell.

IV. Harden some prothalli with alcohol, or with picric acid
and then with alcohol. The preparations described below may



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176 • PRACTICAL BOTANY

also be made from fresh material, but the results will not be
nearly so good as if one of the above methods of fixing and
hardening be adopted.

Hold a prothallus thus prepared between pieces of pith, or
embed as directed on p. 173 : then cut sections perpendicularly
to the surface of the prothallus, so as to pass through the cushion,
following the organic axis from base to apex. Mount in
glycerine, and examine first with a low power.

The lower surface may easily be recognized by the presence
of root-hairs : on this lower side, chiefly near to the apical end
of the section, which is characterized by its small cells with
thin walls, will be found archegonla: these may be recognized
by the multicellular neck, which projects beyond the surface of
the section. In some cases the canal of the neck may appear
of a deep brown colour : this is the case in old archegonia
which have not been fertilized, and they should be disregarded.
Select one archegonium of full size and healthy appearance, and
examine it under a high power.

Observe that it consists of —

A. The central aeries of three cells, which may be distin-
guished as —

a. The canal-cell ; this is oblong in form, and its walls are
subject to mucilaginous degeneration : it occupies the channel
of the neck, and has been above alluded to as being visible
when the neck of the archegonium is seen from above.

b. The small ventral canal-cell, which lies immediately
below the oblong canal-cell, and is of rounded form.

c. The oosphere, or ovum, which is of relatively large size,
and roughly spherical form : it is embedded in the tissue of the
cushion, and consists of a dense mass of granular protoplasm.

B. The neck, which is composed of cells arranged in four
rows, constituting together a cylinder or tube, one layer of
cells in thickness : this projects from the surface of the pro-
thallus, and incloses the cells (a) and (6) of the central series,
while (c)j the ovum, is embedded in, and surrounded by, cells
of the cushion.

At the end of the section more remote from the apex
may be found antheridia. Select one fully developed, and



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ASPIDIUM— YOUNG SPOROPHYTE 177

it will be seen to consist essentially of an outer wall one
layer of cells in thickness : this incloses a central mass of
cells, the contents of which may be seen to be rounded off, and
to have assumed the form of a closely coiled spiral : these are
the spermatocytes or mother-cells of the spermatozoids.

The dehiscence of the antheridia, the escape of the sperma-
tozoids, and their movement, should be observed with particular
attention in fresh prothalli mounted in water ; also the opening
of the apex of the neck of the archegonium ; in both cases the
process depends upon a mucilaginous degeneration of cell-walls
of the inner cells, and a subsequent swelling by taking up
water, and consequent rupture of the outer walls. Further, the
movements of the living spermatozoids may be followed, and
the act of fertilization observed : the spermatozoids pass through
the mass of mucilage which fills the neck of the archegonium,
and finally coalesce with the ovum.



C.—THE YOUNG SPOROPHYTE, OR FERN-PLANT.

I. The result of the process of fertilization of the ovum by
the spermatozoids is the development of a new Fern-plant (the
Sporophyte), and in cultures which have been continued for
some months such young Fern-plants may be clearly seen
attached to the prothalli, but one prothallus produces only one
young Fern-plant.

Select a prothallus to which a young Fern -plant is thus
attached, and wash from it the soil which adheres to it.
Examine it with a lens, and observe—

1. That the prothallus itself is similar in form and structure
to those before observed.

2. That the young Fern-plant is firmly attached to its under
surface by a lateral protrusion (foot).

3. That the young Fern-plant consists of the following
parts : —

a. A root, which turns downward into the soil.

b. A lateral protrusion, the foot, which maintains a close

N



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178 PRACTICAL BOTANY

physiological connection between the pro t hall us and the Fern-
plant.

c. A first leaf, or cotyledon, with an elongated petiole, and
bifurcating, expanded, upper part : this usually grows upwards
through the depression at the apex of the prothallus.

d. Between the base of the cotyledon and the foot is the apex
of the stem, which continues its growth, and produces new
leaves.



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BRYOPHYTA

A.— MUSCI

POLYTRICHUM COMMUNE, L.

A.— GENERAL EXTERNAL CHARACTERS

1. Observe in well-grown specimens of this Moss taken in
spring or early summer —

i. The erect stem, 1 which may attain a considerable length,
branching but rarely :

2. The leaves, 1 of relatively small size, and simple form ;
their arrangement is on a complicated plan : at the base of the
stem note —

3. A dense mat of rhisoids of brownish colour.

At the apex of some specimens will be found merely a bud,
composed of young leaves of the vegetative type ; other
specimens will bear at their apex —

4. Perigonia, or pericheetia; cup-like rosettes of leaves,
which assume a bright reddish or orange colour, and protect
the antheridia; other specimens again may bear at their
apex —

5. The mature sporogoninm or spore-capsule, of which the

1 Though the terms "stem" and " leaf" are used here, it must be distinctly borne
in mind that the members thus named, being parts of the oophyte generation
are not homologous with, but at most only analogous to the stem and leaf
of vascular plants, which art parts of the sporophyte generation.

N 2



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180 PRACTICAL BOTANY

head or theca is supported on a long stalk, or seta. Note in
specimens which are not too ripe —

a. The calyptra, a dry fibrous hood, covering the apex of the
sporogonium : beneath this is —

b. The lid-like operculum with its terminal beak : this lid
may be easily detached, disclosing —

c. The pale-grey epiphraffm, which appears as a transverse
membrane, attached at its margin to the capsule by a number
of short teeth of the peristome.

d. At the base of the theca observe a swelling called the
apophysis,

e. By carefully removing the leaves from the apex of a plant
which bears a sporogonium, it may be seen that the base of the
seta is enveloped by a closely fitting sheath, the veil or ▼aginula,
the origin of which will be explained later.



B.— MICROSCOPIC INVESTIGA TION.
Oophyte Generation.

II. Cut transverse sections of a mature stem of Polytrichum:
mount some in glycerine, others in chlor-zinc-iodine, or in
iodine solution : examine them first under a low power, and
observe in those mounted in glycerine —

i. The outline of the section, which is usually more or less
clearly triangular.

2. The dense reddish-brown band of peripheral sclerenchyma,
which passes over gradually into —

3. A broad, thinner-walled band of tissue, which may be
termed the cortex : this finally surrounds —

4. A central mass of firm, yellow-walled tissue.

Examine these several tissues in detail, under a high power,
and observe that —

1. At the extreme outer limit is a thin cuticle, with small and