286 



TROPICAL AGRICULTURE 



CHAP. 



and smooth above. The leaves are heart-shaped and 

 The tubers, alternate on the stem. The tubers grow to a large size, 

 weighing usually about ten pounds ; they are palmated in 

 shape, and they are so brittle as to be easily broken. They 

 are of a white or 5'^ellowish colour within, but the white kind 

 is liked best. These yams do not keep in good condition 

 for any length of time after their removal from the ground. 



Guinea Yam. Dloscorea aculeata. — In Jamaica this is 

 Habitat. sometimes called the Afou yam. It is largely cultivated 

 throughout the West Indies, but its native country is 

 Cochin China, and it comes also from Malabar. The stem 

 is round, prickly and much branched. The leaves are 

 broadly heart-shaped, and either alternate or opposite on 

 The tubers, the Stem. The tubers are very large, reaching a length of 

 two or three feet, a diameter of six or eight inches, and a 

 weight of from fifteen to twenty pounds. The interior is of 

 a white or yellow colour, and when cooked the flavour is 

 somewhat bitter. 



The tubers. 



Varieties. 



CUSH-CUSH Yam. Dioscorea triphylla. In Jamaica this 

 is sometimes called the Indian yam ; and, in Guiana, it is 

 known as the buck yam. The stem is roundish, th^ leaves 

 are opposite on the stem, and divided into three leaflets. 

 The tubers are roundish — indeed, something like a potato 

 in shape. They rarely exceed nine inches in length, and 

 three inches in diameter, but they are usually much smaller. 

 It is said to be the smallest and most delicate of all the 

 yams. The plant is prolific, sometimes bearing a dozen 

 tubers on the roots. There are two principal kinds, the 

 white and the red, the latter bearing tubers that are purplish 

 within. 



Sfs^^^^ Soil and Climate.— All the yams require a rich sandy 



loam, deep and friable, for the rich tubers will not be able 

 to develop properly in stiff heavy soils. The white yam, 

 however, will grow well on calcareous soils of a moderate 



