Some plants have stems under the soil as well as above it. These
underground stems resemble roots but can be distinguished from them by
the rings or joints where will be found buds and small scale-like
leaves (Fig. 69). Quitch-grass or wiregrass, Burmuda grass, white
potato and artichoke are examples of underground stems.

Now study the habit of growth of these stems. Notice that:

Some plants grow erect with strong, stiff stems, for example, corn,
sunflower, maple, pine, elm and other trees. Many of these erect stems
have branches reaching out into the air in all directions. Stand under
a tree close to the stem or trunk and look up into the tree and notice
that the leaves are near the outer ends of the branches while in the
centre of the tree the branches are nearly bare. Why is this? If you
remember the work of leaves and the conditions necessary for their
work you will be able to answer this question. Leaves need light and
air for their work, and these erect, branching stems hold the leaves
up and spread them out in the light and air.

Notice that where several trees grow close together, they are
one-sided, and that the longest and largest branches are on the
outside of the group and that they have more leaves than the inner
branches. Why? Why do the trees in thick woods have most of the living
branches and bear most of their leaves away up in the top of the tree?

Some stems instead of standing up erect climb up on other plants or
objects by means of springlike tendrils which twist about the object
and so hold up the slender stem. On the grape vine these tendrils are
slender branches. On the sweet pea and garden pea they are parts of
the leaves. The trumpet creeper and English ivy climb by means of air