MINOR CROPS. 335 



There are several annual species as well as an annual selec- 

 tion of M. alba, namely, Hubbam Clover, wbicb makes rapid 

 growth under South African conditions, and has attracted a 

 great deal of attention lately. The Sweet Clovers contain a 

 bitter substance called cumarin, which renders them unpalat- 

 able to stock, a fact which has restricted their cultivation. 

 Once accustomed to it, though, stock thrive on it. 



Agriculturally, M. alba is much the most important. It 

 grows readily on a variety of soils, heavy and light, rich and 

 poor, well drained and poorly drained. In South Africa it 

 enjoys the reputation of doing well on poor sandy soils — a hap)i \ 

 fact, since being an excellent green-manuring crop, it might 

 well be utilised in renovating worn-out sandy soils. It is 

 drought and alkali-resistant to a high degree. A fine seed bed 

 is required, and 15 to 20 lbs. of seed are used per acre. American 

 experimentalists consider it, on account of its vigorous root 

 system and quick decay of the whole plant, to be one of the best 

 crops for green-manuring. The young growth is less bitter 

 than the older growth and it makes good grazing for stock that 

 will take to it. 



As a hay crop in South Africa it is difficult to see why sweet 

 clover should be superior to the erect growing types of cowpeas. 

 It is highly esteemed by bee-keepers. 



THE SWEET POTATO (Ipomcea batatas). 



The original home of the sweet potato is in the West Indies 

 and Central America. It belongs to the Convolvulace^ or the 

 Morning Glory family, and is a perennial with very much 

 thickened roots, which constitute the edible portion. It seldom 

 produces flowers and rarely, if ever, matures seeds. When in 

 favoured locahties, seeds are produced and planted, new varie- 

 ties may thus be originated. The classification of varieties is 

 based on the shape of the leaf, which is round, lobed or notched. 

 They may also be divided into two groups upon the basis of the 

 amount of w^ater and sugar present — (1) dry sweet potatoes are 

 ones in which the flesh is dry, mealy and yellow; (2) "yams" 

 are sweet potatoes of which the flesh is watery, rich in sugar, 

 soft and gelatinous when cooked. 



Climatic and Soil Eequirements. — For maximum pro- 

 duction it requires a fairly long growing season, free from frost, 

 such as is found along the southern coast belt of the Cape Pro- 

 vince and in the Lowveld areas of the Transvaal Province and 



