80 



Principles of Plant Culture. 



114. The Stem is, generally speaking, the part of the 

 plant that supports the leaves. In exceptional eases, 

 as in the potato (Fig. 34) and quack grass, a part of 

 the stem grows beneath the ground, on which the leaves 

 usually do not develop {underground stems) ; and in a 

 few plants, as in some cacti, the stem performs the 

 whole office of leaves. The stem may be strong enough 

 to support its own weight, as in 

 trees and shrubs, or it may de- 

 pend upon other objects for its 

 support, as in vines, 



115. Nodes and Internodes. 

 Unlike the root, the stem is de- 

 veloped in successive sections, 

 comparable in part to the stor- 

 ies of a building. Each section 

 or story consists of one or more 

 leaves, attached to the distal* 

 end of a portion of the stem. 

 The part of the stem to which 

 the leaf or leaves are attached is 

 called a node and the part be- 

 low the node, or in the stem as 

 a whole, the part between the 

 nodes, is called an internode. 

 The nodes are distinctly marked in the younger stems 

 of most plants by a slight enlargement or by leaf-scars, 

 if the leaves have fallen (Fig. 35). The nodes are 

 centers of vital activity and are points at which lateral 



N— 



Fig. 35. Nodes (N) ; A, 

 ot the box elder, Acer 

 negundo ; B, of the wild 

 grape, Vltls rlparia. 



* Distal means farthest from the point at which growth started. 

 It is opposed to proximal, which means nearest the point of origin. 



