[Illustration: FIG. 22.]

[Illustration: FIG. 23.]

_Gray's First Lessons_. Sect. IV. VII, §4. _How Plants Grow_. Chap. I,
51-62; I, 153.




V.

STEMS.


The stem, as the scholars have already learned, is the axis of the plant.
The leaves are produced at certain definite points called nodes, and the
portions of stem between these points are internodes. The internode,
node, and leaf make a single plant-part, and the plant is made up of a
succession of such parts.

The stem, as well as the root and leaves, may bear plant-hairs. The
accepted theory of plant structure assumes that these four parts, root,
stem, leaves, and plant-hairs, are the only members of a flowering plant,
and that all other forms, as flowers, tendrils, etc., are modified from
these. While this idea is at the foundation of all our teaching, causing
us to lead the pupil to recognize as modified leaves the cotyledons of a
seedling and the scales of a bud, it is difficult to state it directly
so as to be understood, except by mature minds. I have been frequently
surprised at the failure of even bright and advanced pupils to grasp this