338 SCIENCE IN AFRICA 



though general information can be found in text-books of tropical 

 agriculture. The Royal Botanic Gardens, Kew, has published as 

 Additional Series XII of the Kew Bulletin a list of the cultivated 

 crop-plants of the tropics and subtropics grown in the British 

 Empire and the Anglo-Egyptian Sudan which shows their cultural 

 distribution (Sampson 1936). For West Africa, especially Nigeria, 

 Faulkner and Mackie (1933) devote several chapters to crops. 

 Leppan and Bosman (1923) deal with the crops of South Africa. 

 For French West Africa Perrot (1930) has written a large volume 

 on vegetable productions, both wild and cultivated. In 1935 ^^^ 

 Ministry for Colonies in Brussels produced a series of small pam- 

 phlets on the crops of the Belgian Congo, namely cotton, cacao, 

 rubber, palm-oil, other vegetable oils, copal, and fibres. Most of 

 these include a useful list of selected publications dealing with the 

 crops concerned. Reference is made to special publications in 

 the following pages, after the historical notes on Africa's crop- 

 plants. 



The order in which the various crop-plants are discussed is 

 based on a questionnaire used in the preparation by the Royal 

 Botanic Gardens of the list (Sampson 1936) mentioned above. 



ORIGIN OF CROP-PLANTS 



The cultivation of crop-plants in Africa dates back to pre- 

 historic times and the continent has made valuable contributions 

 to the crop-plants of the Old World tropics. There is little doubt 

 that the sorghum crop originated in Africa and that it has spread 

 from there to Asia, where it is grown from Asia Minor to Korea 

 and is perhaps the most valuable dry-land cereal of the more 

 tropical parts. To-day most of the races of sorghum with their 

 numerous varieties are confined to Africa, and it is a matter for 

 astonishment how these races have been maintained and evolved 

 in a country where agriculture is based on shifting cultivation and 

 only primitive methods of grain storage are known. 



Similarly the bulrush millets {Pennisetum spp.) have been evolved 

 in Africa and recent botanical research has shown that more than 

 one wild species of this genus were involved in their production. 

 There are numerous races in Africa and the crop is represented in 



