FORMS OF ROOTS 



23 



In the dodder, as is shown in Fig. 16, the seedling parasite is 

 admirably adapted to the conditions under which it is to live. 

 Eooted at first in the ground, it develops a slender, leafless stem, 

 which, leaning this way and that, no sooner conies into perma- 

 nent contact with a congenial host than it produces sucking 

 roots at many points, gives up further growth in its soil roots, 

 and lengthens rapidly on the strength of the supplies of ready- 

 made sap which it obtains from the host. 



30. Forms of roots. The primary root is that which proceeds 

 like a downward prolongation directly from the lower end of the 



FIG. 17 FIG. 18 FIG. 19 



A tap root Fibrous roots Fleshy and clustered roots 



hypocotyl. In many cases the mature root system of the plant 

 contains one main root much larger than any of its branches. 

 This is called a tap root (Fig. 17). 



Such a root, if much thickened, may assume some such form 

 as that of the carrot, parsnip, beet, turnip, or radish, and is called 

 a fleshy root. Some plants produce a cluster of roots from the 

 lower end of the hypocotyl. Such roots often become thickened, 

 as in the sweet potato and the dahlia (Fig. 19). 



Eoots of grasses, etc., are thread-like, and known as fibrous 

 roots (Fig. 18). 



