SPONGIOLES. 63 
than there is now demand for. Such buds are, therefore, merely adventitious. 
On this account it would seem that those roots, commonly so called, which do 
naturally and uniformly produce buds, are with propriety described by modern 
writers as subterranean stems; as the root-stalk of the sweet flag (Calamus), the 
bulb of the tulip, or the tuber of the potato. 
141. The summit of the root, or that part which connects it to 
the ascending axis, is designated as the collum, or neck. 
a. Strictly speaking, this is the only stationary part of the plant. Occupying 
the centre of motion’ between the ascending and descending axis, every enlarge- 
ment that takes place upon its upper surface arises into the air, while all below it 
descends into the earth. 
142. The parts of the root which require especial notice, are 
the caudex, fibrils, and. spongtoles. 
a. The caupEx (stock) is the main body of the root. 
6. The riprizts are the finer branches of the root, sent off 
from the caudex. ‘These are the true roots. 
c. The sponGioues are the tender and delicate extremities of 
the fibrils; and, since the latter lengthen only by accretions 
made to these extremities, these are their growmmg points. 
143. The form of the root is much diversified in different 
plants, but the principal varieties which have received distinct- 
ive names, are the following :— 
144. Ramose (branching). This root consists of ramifications 
sent off from the main root, like the branches of a tree, but in 
no determinate order. Such are the roots of most trees and 
shrubs. (Fig. 20.) | | 
a. There is a strong analogy between the roots of a tree and its branches. In 
many instances they may be made to perform, each the functions of the other; 
that is, the tree may be inverted, and the branches will become roots and the roots 
put forth leaves like the branches. The willow and the maple may be thus 
inverted without injuring their vitality. 
b. A branch may often be made to put forth roots instead of leaves. If a 
branch (offset) of the willow or currant (Ribes) be inserted into the ground, cither 
by the lower or the upper end, or by both at once, it will take root and flourish. 
Other trees, as the mulberry (Morus) may be multiplied by layers. A branch is 
bent and inserted into the ground by the apex. When it has taken root it is 
severed from the parent stock, and becomes a perfect tree. 
c. The roots of a tree extend in all directions, and to considerable distances. 
This distance is at least equal to the extent of the branches, and often much 
greater. Those of the a embrace an area of 300 feet diameter, of the poplar, 
6 
