THE ANNONACEOUS FRUITS 185 



The soil best suited to this species is probably a loose, fairly 

 rich, deep loam. It has done well, however, on shallow sandy 

 soils in south Florida. F. S. Earle has found in Cuba that 

 liberal applications of fertilizer will increase greatly the amount 

 of fruit produced. The formula used is the same as that 

 recommended for . the sugar-apple. Little attention has yet 

 been given to the cultural requirements of the plant. 



The soursop, grown from seed, comes into bearing when three to 

 five years old. The season of ripening in Mexico and the West 

 Indies is June to September ; in Florida it is about the same. 



Mature trees rarely bear more than a dozen good fruits in a 

 season. . Oftentimes there are produced numerous small, 

 malformed, abortive fruits which are of no value. These are 

 due to insufficient pollination, only a few of the carpels develop- 

 ing normally, the remainder being unable to do so because they 

 are not pollinated. The same phenomenon often occurs in the 

 eherimoya, and, less commonly, in the sugar-apple and bullock's- 

 heart. 



Seedling trees differ in the amount of fruit they yield. Only 

 the most productive should be selected for propagation. It 

 may be possible still further to increase their productiveness 

 by attention to pollination, and it has been shown that proper 

 manuring is a great aid. Since the fruits are commonly of 

 large size, it cannot be expected that so small a tree will produce 

 many ; still, the average seedling does not bear more than a 

 small proportion of the crop it could safely carry to maturity, 

 and the object of future investigations should be to obtain 

 varieties which will be more productive. 



In various parts of the world the tree is attacked by several 

 scale insects, and the fruits by some of the fruit-flies, notably the 

 Mediterranean fruit-fly. 



Propagation of the soursop is usually effected in the tropics by 

 seed. Choice varieties which originate as chance seedlings, 

 however, can only be perpetuated by some vegetative means. 



