280 THE CHIEF SOUTHERN AGRICULTURAL CROPS 



Successive plantings are necessary in order to keep up 

 continuous shipments. Egg plants and peppers grow 

 and yield well for a long period, but the former are 

 subject to a stem blight or wilt that frequently 

 causes heavy losses. 



Among the distinctively tropical vegetables there 

 are three that deserve some especial mention from 

 their importance in the local markets and as a 

 source of home food supply, though as yet they are 

 unknown in Northern commerce. These are yams, 

 cassava, and malangas, or yautias. 



Yams (^Dioscorea) . — The true yams are the large, 

 irregular starchy tubers of tall-growiiig vines belong- 

 ing to various species of Dioscorea. Sweet potatoes 

 are often called yams in the Southern states, but this 

 is not the proper use of the word. Yams require a 

 moist, rich soil that is well supplied with vegetable 

 matter. They are planted in large hills or in rather 

 high ridges in order to secure perfect drainage, and 

 tall stakes are necessary for the vines to climb on. 

 Pieces of the tubers are planted for seed the same as 

 with the potato. It requires about twelve months 

 for the crop to mature. The tubers are large, often 

 weighing several pounds each. They are used in 

 the same manner as potatoes, but they are more 

 nutritious and constitute one of the most important 

 of the tropical food crops. The tubers keep indefi- 

 nitely while undisturbed in the ground, but they 

 cannot be kept long after digging. 



Cassava QManihot). — The sweet cassava, or 

 "yuca," as it is called in Spanish-speaking countries, 

 is another tropical food crop of much importance. The 



