the stem runs underground, _suckers_. The gardener imitates them in
the process called layering, that is, bending down an erect branch and
covering it with soil, causing it to strike root. When the connecting stem
is cut, a new plant is formed. Long and leafless stolons, like those of
the Strawberry are called _runners_. Stems creep below the ground as well
as above. Probably the pupil will think of some examples. The pretty
little Gold Thread is so named from the yellow running stems, which grow
beneath the ground and send up shoots, or suckers, which make new plants.
Many grasses propagate themselves in this way. Such stems are called
_rootstocks_. "That these are really stems, and not roots, is evident
from the way in which they grow; from their consisting of a succession of
joints; and from the leaves which they bear on each node, in the form
of small scales, just like the lowest ones on the upright stem next the
ground. They also produce buds in the axils of these scales, showing the
scales to be leaves; whereas real roots bear neither leaves nor axillary
buds."[1] Rootstocks are often stored with nourishment. We have already
taken up this subject in the potato, but it is well to repeat the
distinction between stems and roots. A thick, short rootstock provided
with buds, like the potato, is called a _tuber_. Compare again the corm of
Crocus and the bulb of Onion to find the stem in each. In the former, it
makes the bulk of the whole; in the latter, it is a mere plate holding the
fleshy bases of the leaves.

[Footnote 1: Gray's First Lessons, revised edition, 1887, page 42.]

2. _Movements of Stems.--_Let a glass thread, no larger than a coarse
hair, be affixed by means of some quickly drying varnish to the tip of the
laterally inclined stem of one of the young Morning-Glory plants in the
schoolroom. Stand a piece of cardboard beside the pot, at right angles to
the stem, so that the end of the glass will be near the surface of the