Modified Parts. 



139 



FIG. 68. 

 Artichoke tuber. After GRAY. 



in two almost continuous rows 

 (see Fig. 17). In these cases, 

 the real nature of the roots 

 is not much masked. The 

 aerial roots of orchids and 

 the parasitic roots of Cuscuta, 



although modified for absorption under special conditions, 

 have still retained much of the appearance of typical roots. 

 The supporting roots of the 

 banyan, however, extending 

 to the ground, have the 

 general appearance of stems, 

 but their identity is 

 easily determined by 

 the method and 

 place of their ori- 

 gin on the branches. 

 112. Modified 

 Stems. Stems are 

 frequently modified 

 to grow beneath the 

 surface, and there 

 attain considerable 

 size for the purpose 

 of storage ; 

 the potato 

 and artichoke 

 are good ex- 

 amples. Al- 

 though grow- 

 ing beneath 

 the ground 

 like roots, and 



FIG. 69. 



Nelumbo lutea. v, a tuber which has survived the winter; x 

 and w, horizontal offshoots growing beneath the mud, serv- 

 ing the purpose of multiplication ; y, shoot growing deeper 

 preparatory to the thickening of some of its internodes for 

 the purpose of storage, as in v. The horizontal lines be- 

 neath the leaves indicate the surface of the water. 



