AGRICULTURAL BOTANY 



The Stem. --The stem of the plant, the part from 

 which all the other parts of the plant spring, is the 

 axis of the plant. Some stems stand erect and support 

 the whole plant, as in trees and shrubs ; others lie on 

 the ground or cling to some object for support, as vines ; 

 still others grow under- 

 ground, and thus seem 

 like roots, but that they 

 are really stems may 

 readily be discovered. 



Underground Stems. 

 Among the under- 

 ground stems of inter- UJSt.- 

 est to the farmer are 

 the potato, the quack 

 grass, and the wild morn- 

 ing glory. 



The potato is the 

 thickened end of an 

 underground stem. Its 

 true stem character is 

 shown by the buds, 

 eyes, it bears. An under- 

 ground stem like the 

 potato is called a tuber. 

 The sweet potato, on the contrary, is an enlargement 

 of the root. 



The underground stems of the quack grass and the 

 wild morning glory make these two plants great weed 

 pests. 



Note. Canada thistle has been considered a plant with an under- 

 ground stem, but the running root of this plant lacks nodes, scales, or 

 buds and is therefore properly a root. 



FIG. 55. Potato Plant. 



U si, underground stems; R, roots; the tubers are 

 the thickened ends of the underground stems. 

 (Much reduced. After Frank and Tschirch.) 



