OUTLINE OF STRUCTURAL BOTANY 5 
ing at regular intervals, as at the leaf axils, are lateral roots 
(Fig. 2). 
ica 2 
Still other plants have roots swimming free in water on the sur- 
face of which the body of the plant floats. 
Many plants of the non-flowering class are devoid of roots, but 
with rare exceptions, as, for example, the floating grains constitut- 
ing the plants of Wolffa, flowering plants are 
provided with roots, terrestrial, aerial or 
aquatic. 
Although the roots of a plant have their 
origin in the radicle of the em- 
bryo they may exist in large 
numbers having the appear- 
ance of arising from as many 
distinct origins, but at the 
very base of the stem. Thus, 
among the plants of the great 
grass family, a group of roots 
seems to spring from the same 
Fic. 3—Fibrous rootslevel and to proceed downward 
of grass. 2 
with few or no branches. In 
fact these numerous roots have sprung from the 
radicle all at nearly the same level and have so 
far monopolized its structure that they prac- 
tically, though not theoretically, arise from the 
base of the stem. Roots of this kind, arising in 
numbers from apparently the same level are 
known as compound or fibrous roots, a form 
common among plants with parallel-veined 
leaves—(monocotyledonous plants) (Fig. 3). In 
ease of plants with net-veined leaves—dicotyle- 
donous plants)—the axis usually extends downward as a tap root. 
Fic. 4 
