hed form of the young stem. Their attention should also be drawn to the
root-hairs, which are well seen in Corn, Wheat, and Oats. They absorb the
liquid food of the plants. A secondary office is to hold the seed firmly,
so that the caulicle can enter the ground. This is shown in Red Clover,
which may be sown on the surface of the ground. It puts out root-hairs,
which attach themselves to the particles of sand and hold the seed. These
hairs are treated more fully in the lessons on roots.

[Footnote 1: The Power of Movement in Plants. By Charles Darwin. London.
John Murray, 1880.]

[Footnote 1: Reader in Botany. IV. Movements of Seedlings.]

5. _Leaves of Seedlings_.--Coming now to the question as to the number of
leaves at each joint of the stem, the Morning-Glory, Sunflower, and Bean
will present no difficulty, but probably all the pupils will be puzzled by
the Pea. The stipules, so large and leaf-like, look like two leaves,
with a stem between, bearing other opposite leaves, and terminating in a
tendril, while in the upper part it could not be told by a beginner which
was the continuation of the main stem. For these reasons I left this out
in the questions on the Pea, but it should be taken up in the class. How
are we to tell what constitutes a single leaf? The answer to this question
is that buds come in the _axils_ of single leaves; that is, in the inner
angle which the leaf makes with the stem. If no bud can be seen in the
Pea, the experiment may be tried of cutting off the top of the seedling
plant. Buds will be developed in the axils of the nearest leaves, and it
will be shown that each is a compound leaf with two appendages at its
base, called stipules, and with a tendril at its apex. Buds can be forced
in the same way to grow from the axils of the lower scales, and even from
those of the cotyledons, and the lesson may be again impressed that organs
are capable of undergoing great modifications. The teacher may use his own
judgment as to whether he will tell them that the tendril is a modified
leaflet.

[Illustration: FIG. 9. 1. Grain of Indian Corn. 2. Vertical section,
dividing the embryo, _a_, caulicle: _b_, cotyledon; _c_, plumule. 3.
Vertical section, at right angles to the last.]

6. _Monocotyledons_.--These are more difficult. Perhaps it is not worth
while to attempt to make the pupils see the embryo in Wheat and Oats. But
the embryo of Indian Corn is larger and can be easily examined after long
so