1. There is an astonishing amount to be learned from naked branches,
and, if pursued in the right way, the study will be found exceedingly
interesting. Professor Beal, in his pamphlet on the New Botany,[1] says:--
"Before the first lesson, each pupil is furnished or told where to procure
some specimen for study. If it is winter, and flowers or growing plants
cannot be had, give each a branch of a tree or shrub; this branch may be
two feet long. The examination of these is made during the usual time for
preparing lessons, and not while the class is before the teacher. For the
first recitation each is to tell what he has discovered. The specimens are
not in sight during the recitation. In learning the lesson, books are not
used; for, if they are used, no books will contain a quarter of what the
pupil may see for himself. If there is time, each member of the class is
allowed a chance to mention anything not named by any of the rest. The
teacher may suggest a few other points for study. The pupils are not told
what they can see for themselves. An effort is made to keep them working
after something which they have not yet discovered. If two members
disagree on any point, on the next day, after further study, they are
requested to bring in all the proofs they can to sustain their different
conclusions. For a second lesson, the students review the first lesson,
and report on a branch of a tree of another species which they have
studied as before. Now they notice any point of difference or of
similarity. In like manner new branches are studied and new comparisons
made. For this purpose, naked branches of our species of elms, maples,
ashes, oaks, basswood, beech, poplars, willows, walnut, butternut,
hawthorns, cherries, and in fact any of our native or exotic trees or
shrubs are suitable. A comparison of the branches of any of the evergreens
is interesting and profitable. Discoveries, very unexpected, are almost
sure to reward a patient study of these objects. The teacher must not
think time is wasted. No real progress can be made, till the pupils begin
to learn to see; and to learn to see they must keep trying to form the
habit from the very first; and to form the habit they should make the
study of specimens the main feature in the course of training."
[Footnote 1: The New Botany. By W.J. Beal. Philadelphia, C.H. Marot, 814
Chestnut St., 1882. Page 5.]
HORSECHESTNUT (_Æsculus Hippocastanum_).
We will begin with the study of a branch of Horsechestnut.[1] The pupils
should examine and describe their specimens before discussing them in the
class-room. They will need some directions and hints, however, to enable
them to work to any advantage. Tell them to open both large and small
buds. It is not advisable to study the Horsechestnut bud by cutting
sections, as the wool is so dense that the arrangement cannot be seen in
this way. The scales should be removed with a knife, one by one, and the
number, texture, etc., noted. The leaves and flower-cluster will remain
uncovered and will be easy to examine. The gum may be first removed by
pressing the bud in a bit of paper. The scholars should study carefully
the markings on the stem, in order to explain, if possible, what has
caused them. The best way to make clear the meaning of the scars is to
show them the relation of the bud to the branch. They must define a bud.
Ask them what the bud would have become the next season, if it had been
allowed to develop. It would have been a branch, or a part of one. A bud,
then, is an undeveloped branch. They can always work out this definition
for themselves. Conversely, a branch is a developed bud, or series of
buds, and every mark on the branch must correspond to something in the
bud. Let them examine the specimens with this idea clearly before their
minds. The lesson to prepare should be to write out all they can observe
and to make careful drawings of their specimens. Ask them to find a way,
if possible, to tell the age of the branch.
[Footnote 1: The pupils should cut their names on their branches and keep
them. They will need them constantly for comparison and reference.]
At the recitation, the papers can be read and the points mentioned
thoroughly discussed. This will take two lesson-hours, probably, and the
drawing may be left, if desired, as the exercise to prepare for the second
recitation.
[1]The buds of Horsechestnut contain the plan of the whole growth of the
next season. They are scaly and covered, especially towards the apex, with
a sticky varnish. The scales are opposite, like the leaves. The outer
pairs are wholly brown and leathery, the succeeding ones tipped with
brown, wherever exposed, so that the whole bud is covered with a thick
coat. The inner scales are green and delicate, and somewhat woolly,
especially along the lapping edges. There are about seven pairs of
scales. The larger terminal buds have a flower-cluster in the centre, and
generally two pairs of leaves; the small buds contain leaves alone, two or
three pairs of them. The leaves are densely covered with white wool, to
protect them from the sudden changes of winter. The use of the gum is to
ward off moisture. The flower-cluster is woolly also.
[Footnote 1: All descriptions are made from specimens examined by me.
Other specimens may differ in some points. Plants vary in different
situations and localities.]
The scars on the stem are of three kinds, leaf, bud-scale, and
flower-cluster scars. The pupils should notice that the buds are always
just above the large triangular scars. If they are still in doubt as to
the cause of these marks, show them some house-plant with well-developed
buds in the axils of the leaves, and ask them to compare the position of
these buds with their branches. The buds that spring from the inner angle
of the leaf with the stem are _axillary_ buds; those that crown the stems
are _terminal_. Since a bud is an undeveloped branch, terminal buds carry,
on the axis which they crown, axillary buds give rise to side-shoots. The
leaf-scars show the leaf-arrangement and the number of leaves each year.
The leaves are opposite and each pair stands over the intervals of the
pair below. The same is observed to be true of the scales and leaves
of the bud.[1] All these points should be brought out by the actual
observation of the specimens by the pupils, with only such hints from the
teacher as may be needed to direct their attention aright. The dots on the
leaf-scar are the ends of woody bundles (fibro-vascular bundles) which, in
autumn, separated from the leaf. By counting these we can tell how many
leaflets there were in the leaf, three, five, seven, nine, or occasionally
six or eight.
[Footnote 1: Bud-scales are modified leaves and their arrangement is
therefore the same as the leaves. This is not mentioned in the study of
the Horsechestnut bud, because it cannot be proved to the pupils, but the
transition is explained in connection with Lilac, where it may be clearly
seen. The scales of the bud of Horsechestnut are considered to be
homologous with petioles, by analogy with other members of the same
family. In the Sweet Buckeye a series can be made, exhibiting the gradual
change from a scale to a compound leaf. See the Botanical Text-Book, Part
I, Structural Botany. By Asa Gray. Ivison, Blakeman, Taylor and Co., New
York, 1879. Plate 233, p. 116.]
[Illustration: FIG. 13.--Horsechestnut. I. Branch in winter state: _a_,
leaf-scars; _b_, bud-scars; _c_, flower-scars. 2. An expanding leaf-bud.
3. Same, more advanced.]
_The Bud Scale-Scars_. These are rings left by the scales of the bud and
may be seen in many branches. They are well seen in Horsechestnut. If the
pupils have failed to observe that these rings show the position of former
buds and mark the growth of successive years, this point must be brought
out by skilful questioning. There is a difference in the color of the more
recent shoots, and a pupil, when asked how much of his branch grew the
preceding season, will be able to answer by observing the change in color.
Make him see that this change corresponds with the rings, and he will
understand how to tell every year's growth. Then ask what would make the
rings in a branch produced from one of his buds, and he can hardly fail to
see that the scales would make them. When the scholars understand that the
rings mark the year's growth, they can count them and ascertain the age
of each branch. The same should be done with each side-shoot. Usually the
numbers will be found to agree; that is, all the buds will have the
same number of rings between them and the cut end of the branch, but
occasionally a bud will remain latent for one or several seasons and then
begin its growth, in which case the numbers will not agree; the difference
will be the number of years it remained latent. There are always many buds
that are not developed. "The undeveloped buds do not necessarily perish,
but are ready to be called into action in case the others are checked.
When the stronger buds are destroyed, some that would else remain dormant
develop in their stead, incited by the abundance of nourishment which the
former would have monopolized. In this manner our trees are soon reclothed
with verdure, after their tender foliage and branches have been killed by
a late vernal frost, or consumed by insects. And buds which have remained
latent for several years occasionally shoot forth into branches from the
sides of old stems, especially in certain trees."[1]
[Footnote 1: Structural Botany, p. 48.]
The pupils can measure the distance between each set of rings on the main
stem, to see on what years it grew best.
_The Flower-Cluster Scars_. These are the round, somewhat concave, scars,
found terminating the stem where forking occurs, or seemingly in the
axils of branches, on account of one of the forking branches growing more
rapidly and stoutly than the other and thus taking the place of the main
stem, so that this is apparently continued without interruption. If the
pupils have not understood the cause of the flower-cluster scars, show
them their position in shoots where they are plainly on the summit of the
stem, and tell them to compare this with the arrangement of a large
bud. The flower-cluster terminates the axis in the bud, and this scar
terminates a branch. When the terminal bud is thus prevented from
continuing its growth, the nearest axillary buds are developed.[1] One
shoot usually gets the start, and becomes so much stronger that it throws
the other to one side. The tendency of the Horsechestnut to have its
growth carried on by the terminal buds is so strong that I almost feel
inclined to say that vigorous branches are never formed from axillary
buds, in old trees, except where the terminal bud has been prevented from
continuing the branch. This tendency gives to the tree its characteristic
size of trunk and branches, and lack of delicate spray. On looking closely
at the branches also, they will be seen to be quite irregular, wherever
there has been a flower-cluster swerving to one side or the other.
[Footnote 1: The first winter that I examined Horsechestnut buds I found,
in many cases, that the axillary shoots had from a quarter of an inch to
an inch of wood before the first set of rings. I could not imagine what
had formed this wood, and it remained a complete puzzle to me until the
following spring, when I found in the expanding shoots, that, wherever
a flower-cluster was present, there were one or two pairs of leaflets
already well developed in the axils, and that the next season's buds were
forming between them, while the internodes of these leaflets were making
quite a rapid growth. Subsequently, I found the leaflets also in the buds
themselves. I found these leaflets developed on the tree only in the
shoots containing flower-clusters, where they would be needed for the
future growth of the branches. I suppose the reason must be that the
flower-cluster does not use all the nourishment provided and that
therefore the axillary buds are able to develop. It would be interesting
to know what determines the stronger growth of the one which eventually
becomes the leader.]
There is one thing more the pupils may have noticed. The small round dots
all over the young stem, which become long rifts in the older parts, are
breaks in the epidermis, or skin of the stem, through which the inner
layers of bark protrude. They are called lenticels. They provide a passage
for gases in and out of the stem. In some trees, as the Birch, they are
very noticeable.
After discussing the subject thoroughly in the class-room, the pupils
should rewrite their papers, and finally answer the following questions,
as a species of review. I have thus spent three recitations on the
Horsechestnut. The work is all so new, and, if properly presented,
so interesting, that a good deal of time is required to exhaust its
possibilities of instruction. If the teacher finds his scholars wearying,
however, he can leave as many of the details as he pleases to be treated
in connection with other branches.