110 BOTANY 
epidermis and cortex are the same as in dicotyledons, 
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 sealy). 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 axillary, 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: 
