346 SCIENCE IN AFRICA 



mineral matter and protein. They suggest that it could be added 

 with great advantage to the dietaries of mine labourers in South 

 Africa. 



In Nigeria the use of green manuring is being widely inculcated, 

 and Mucuna aterrima and Calopogonium mucunoides have been found 

 most generally suitable for this purpose. The latter also has 

 proved of great value as a cover crop in plantation agriculture in 

 Sierra Leone, French West Africa, and the Belgian Congo. In 

 the Southern Provinces of Nigeria experiments have been made 

 with various pulses with a view to isolating varieties which will 

 serve both as cover crops and green manures, but none has so 

 far been found which will form a really dense cover capable of 

 preventing soil wash and strangling weeds. 



OIL-SEEDS 



The groundnut [Arachis hypogaea) is an early introduction from 

 South America and must soon have become established as an 

 important addition to the crops of the country, for it is recorded 

 that this crop was introduced into Jamaica from West Africa at 

 the time of the slave trade. Many varieties to which names are 

 given are recognized by the people. As an export crop the ground- 

 nut is of most importance in the semi-arid regions of West Africa, 

 where methods of cultivation and the selection of improved strains 

 have been studied in both French and British dependencies. These 

 plants are comparatively easy to work with, since, being self- 

 fertilized, there is no need for precautions in the process of selection. 

 In northern Nigeria there are two types of groundnuts commonly 

 cultivated, one with an upright growth and the other spreading. 

 By the simple expedient of selecting the best plants over a period 

 of five years the upright kind has produced an increased yield of 

 25 per cent, and the spreading kind of 16 per cent. As there is 

 not very much variation in the quality of groundnuts, efforts are 

 directed mainly to producing greater yields. This is especially 

 the case in those areas where groundnuts are grown for purposes 

 of local food supplies rather than for export. 'Rosette' disease is a 

 serious pest in many parts [see Chapter X). The Gambia, lying 

 as it does in the midst of the groundnut region of Senegal, relies 

 almost entirely on exports of this crop : improved methods of cul- 



