110 Botany

epidermis and cortex are the same as in dictyledons,
a well-marked pericycle is seen, and the vascular
bundles, which have no cambium, are scattered through
the ground tissue.
Aerial Stems. -- Erect stems are commonest. Pros-
trate stems spread over the ground and root at the
nodes; climbing stems make use of support to reach
the light without becoming thick; epiphytes grow on
plants without penetrating their tissues; parasites
penetrate and use the sap of the host; stolons, offsets,
and runners are branches rooting at the tip; a sucker
is a shoot rising from below ground.
Underground Stems- A rhizome is horizontal, and
gives off leaves above and roots below. A tuber is
the swollen tip of an underground stem, a bulb has a
conical axis enveloped in thick leaf bases -- two kinds
(tunicated and scaly). A corm is a short fleshy stem
sheathed in membranous leaves. Stools are partly
root and partly stem.
Vegetative reproduction may be by rhizomes,
stools, tubers, stolons, runners, offsets, bulbs, corms,
cuttings, buds, and grafts.
A bud is an undeveloped shoot usually leafy, some-
times flowering. Buds may be axiallary, terminal,
adventitious, accessory.
Roots and stems compared. A summary itself.
Reserve materials - Seeds contain proteins and
carbohydrates (starch, sugar, cellulose), or oil to
support the seedling.
Roots may contain starch, grape sugar, cane sugar,
or inulin, either to produce flower and fruit in the
second year, or to support that year's shoot. Stems
contain starch, sugar, or inulin to support the next
year's shoot. Leaves of bulbs contain carbohydrate,
in the onion to produce flower and fruit in the second
year, and in others to support that year's shoot. Fruit: