The Stem 107

or stem that has its roots established in the ground.
The important thing in both cases is to have the
cambium layer of bud or scion in contact with that of
the stock and to exclude all air carefully from the
point of juction. By this means new plants exactly
like that which produced the bud or scion may be
obtained, in which respect vegetative differs from
seed reproduction. In the latter, for instance, seedlings
raised from stones derived from the choicest peaches
and cherries may give rise to but worthless varieties.

ROOT AND STEMS
Both roots and stems have epidermis, cortex and
stele. In roots, the growing point is protected by a
root-cap, in stems by a sheath of leaves. In roots, wood
and bast are separate, being arranged alternately; in
stems they are united in vascular bundles. Stems
have nodes and internodes, and roots have not. Root
branches originate from the stele, while stem branches
spring from the cortex. Roots are, as a rule, positively
geotropic and hydrotropic, and negatively heliotropic,
while stems are positively heliotropic and negatively
geotropic and hydrotropic. Stems bear leaf buds,
while roots, as a rule do not. Root hairs, too, are an
entirely different thing, and perform a different work,
from the hairs of stems and leave.

RESERVE MATERIALS.
Reserve materials are always found in seeds, but
in some plants they accumulate also in the stems,
roots or leaves. Since the topic has already been, and
will again be discussed, it may be well to give a brief
summary, and this summary, if all tests be duly made,
will give all the assistance required. It may be men-
tioned as a preliminary, that, in testing for starch and
sugar, it is best to add the iodine first. Then, whether
starch is present or not, the Fehling's solution may be