206 THE CHIEF SOUTHERN AGRICULTURAL CROPS 



drying properly, as the quality and market price are 

 very easily injured. 



A number of well-marked varieties are in cultiva- 

 tion. One known as the Creolla is probably most 

 generally planted; it is a hardy, productive, red- 

 seeded kind that thrives under a wide range of con- 

 ditions. Some of the more delicate, white-seeded 

 varieties have a finer flavor and command higher 

 prices in the market. 



Cacao is subject to a considerable number of rather 

 serious diseases. Thrips often do much damage to 

 the young pods. Two or three different fungi cause 

 serious pod rots, and other fungi cause cankers on the 

 stems that greatly weaken and sometimes kill the 

 trees. There is also a root-rot fungus in some re- 

 gions and in Surinam the industry has been almost 

 extinguished by the outbreak of a witches'-broom 



disease. 



Rubber 



Rubber is prepared from the milky juice of a num- 

 ber of species of trees and vines. Only two are of 

 much importance in the American tropics. These 

 are the Mexican rubber (^Castilloa elastica^ and the 

 Brazilian rubber (^Hevea Brasiliensis'). So far, the 

 commercial supply of rubber has mostly come from 

 wild forest trees. Wasteful methods of harvesting 

 which have rapidly exhausted the more accessible 

 sources of supply, and the immense increase in the 

 use of rubber in the arts, long since forcibly called 

 attention to the necessity of producing it by agricul- 

 tural methods. Much money has been expended in 

 making rubber plantations, especially in southern 



