[Footnote 1: See page 34.]

These ribs and veins are the woody framework of the leaf, supporting the
soft green pulp. The woody bundles are continuous with those of the stem,
and carry the crude sap, brought from the roots, into the cells of every
part of the leaf, where it is brought into contact with the external
air, and the process of making food (_Assimilation_ 4) is carried on.
"Physiologically, leaves are green expansions borne by the stern,
outspread in the air and light, in which assimilation and the processes
connected with it are carried on."[1]

[Footnote 1: Gray's Structural Botany, p. 85.]

The whole leaf is covered with a delicate skin, or epidermis, continuous
with that of the stem.[1]

[Footnote 1: Reader in Botany. XI. Protection of Leaves from the Attacks
of Animals.]


2. _Descriptions_.--As yet the pupils have had no practice in writing
technical descriptions. This sort of work may be begun when they come to
the study of leaves. In winter a collection of pressed specimens will be
useful. Do not attach importance to the memorizing of terms. Let them be
looked up as they are needed, and they will become fixed by practice. The
pupils may fill out such schedules as the following with any leaves that
are at hand.

SCHEDULE FOR LEAVES.