iooi ami nun chops, no. 



173 



taproot it has clustered roots which are enlarged. The 

 enlarged portions of the roots arc called tuberous 

 roots. Fig. <; (pigs H>) shows the enlarged roots of 

 the sweet potato. The enlarged portions are provided 

 With small rootlets which draw food from the soil. 

 Thr taben ol the Irish potato, on the other band, are 

 not true roots; they are the 

 enlarged parts of under- 

 ground steins. Fig. 

 shows the tuber of the Irish 

 potato, and you will notice 

 that the tubers, unlike the 

 tuberous roots of the sweet 

 potato, have no rootlets. 

 Iloth of these crops arc per- 

 ennials; but sinee they are 

 grown for their tubers a 

 fresh crop must be planted 

 each year, and as cultivated 

 crops they are practically 

 annuals. Sweet potatoes 

 "arc sometimes grown for 

 cattle food, but Irish potatoes are used almost exclu- 

 sively for human food. The soil best suited to the 

 sweet potato is a warm, well-drained, sandy loam, 

 rop will not do wejl in a heavy or wet soil. The 

 Irish potato require! for its best development richer 

 soil than the sweet potato. For both crops the soil 

 most be well drained and < ultivated, and well supplied 

 with moisture, though not wet. The sweet potato does 

 best in a temperate or warm climate, and makes but 



Fig. 28.— Tubers and root* of 

 the Irish potato. (Original draw- 

 ing from photograph.) 



