LKSSON 5.] 



MOKI'IIOLOGV OF KOOTS. 



31 



a tree exposes to the air, as 

 twigs. 



Gi). Tlie absorl)iiig surface of 

 it appears to be, on account ol 



compared with the surface of its 



much 



thuu 



I'oots IS very 



the rool-hain, 

 or slender fibrils, which abound on the Iresh and 

 new jiarts of roots. These may be seen with 

 an ordinary magnify ing-ghiss, or even by ihe 

 naked eye in many eases ; as in the root of a 

 seedling Maple (Fig. oH), where the surface is 

 thickly clothed with them. They are not root- 

 lets of a smaller sort ; but, when more magnified, 

 are seen to be mere elongations of the surface 

 of the root into slender tubes, which through 

 their very delicate walls imbibe moisture from 

 the soil with great avidity. They are com- 

 monly much longer than those shown in Fig. 

 5G, which represents only the very tip of a root 

 moderately magnified. Small as they are indi- 

 vidually, yet the whole amount of absorbing 

 surface added to the rootlets by the countless 

 numbers of these tiny tubes is very great. 



70. Roots intend- 

 ed mainh' for ab- 

 sorl)ing branch free- 

 ly, and are slender 

 or thread-like. When the root is prin- 

 cipally of this character it is said to be 

 Jibrous ; as in Indian Corn (Fig. 42), 

 and other grain, and to some extent in 

 all annual ])lanfs (11). 



71. Till- Kool as n Slorrlioiisr of Fonil. 

 In biennial and many peremiial herbs 

 (41), (he root answers an additional 

 purpose. In the course of the sea-^on it 

 becomes a storehouse of nourishment, 

 and enlarges or thickens as it receives 

 the accumulation. Such roots are said 



to be jieslnj : and difi'erent names are applied to them according to 



FIG. 57 58, M. FnriiiK of ne»liy ..r lliirkeni-d rcN.U. 



