18 



OBGANOGBAPHY. 



it is napiform (Lat. napis, turnip ; Fig. 5) ; when spindle- 

 shaped, or thick in the middle, and tapering to both ends, 



it is said to be fusiform (Lat. 

 ' -r?^ xssii^^b. i^. fii^^> spindle ; Fig. 6). 

 fe^^-a ®^^^^ft £zSk ^°* There may grow from 



the plantlet, when a seed 

 sprouts, several roots, instead 

 of a single one, as in the 

 Indian Corn, Wheat, Pea, etc. 

 (Fig. 1, etc.) In such case 

 they are called multiple 

 primary roots. Sometimes they become enlarged, as in 

 the Sweet-potato, Dahlia, etc., and thus serve as reservoirs 

 of plant food. They are then said to be tuberous (Fig. 

 7). In grasses and many other plants they are numerous 

 and thread-like, and are called fibrous roots (Fig. 8). 



11. Secondary roots may arise from the different parts 

 of the plant, — stem and branches, — whether above or 

 below ground. They are 

 called adventitious roots. 

 They are common in creep- 

 ing plants especially at the Ks-a-w m,i vu'iirA kxni 

 joints, and their production ■f 'mS.'^^ k'^-'-Af K/'v.^ 

 is favored by contact with 

 moist soil. In the Trumpet 



Creeper, Poison Ivy, etc., "' " " * ^-+ "' i^'Kv 



they assist the plant in climb- "^ 



ing, and, since they do not grow into the ground, they 

 are called aerial roots. 



12. Aerial roots are more common in moist tropical 



Fig. 4. A conical root. Fig. 5. A napiform root. Fig. 6, A fusiform root. 

 I Fig. 7. Tuberous roots. Fig. 8. Fibrous roots. 



