340 SCIENCE IN AFRICA 



cities of Nigeria, where the indigo dyeing vats are situated, indi- 

 cate the great age of this industry. 



Africa possesses several root crops pecuhar to the continent. At 

 least three species of Dioscorea, two of which exist in many varieties 

 at the present day, are derived from wild African species. This 

 culture is mainly confined to West Africa where doubtless these 

 cultigens originated. Besides yams, the Hausa or Madagascar 

 potato [Coleus dysentericus) is an African crop which is widely dis- 

 tributed. Plectranthus floribmidus, the Kafir potato, belongs to the 

 same family of plants. In Southern Nigeria there is a leguminous 

 root crop [Sphenostylis stenocarpa) , whose flowers resemble those of 

 the cow pea. 



Of crop-plants received from Asia, the banana, which was being 

 grown in the extreme west of Africa when Columbus first dis- 

 covered America, was first introduced from there to the New 

 World. In Hakluyt's voyages mention is made of the people of the 

 Guinea coast bringing presents of bananas and oranges to the 

 ships which traded there. The greater yam came from Asia, and 

 there are numerous plants of Asiatic origin which are found near 

 the east coast of Africa. East Africa also received an important 

 pulse crop from Asia, Phaseolus aureus, the green gram of India. 

 This is now widely distributed in East and Central Africa. 



There is no doubt that the slave trade greatly contributed to 

 the variety of crops which are now grown in Africa. It has been 

 stated that the Portuguese deliberately introduced maize, the 

 groundnut, the cassava, and the sweet potato from America into 

 what is now Angola; for they realized that the frequent famines 

 which occurred in that part of Africa greatly reduced the size and 

 value of their living cargo. Judging, however, by the numerous 

 varieties of these three crops which exist in Africa there must have 

 been numerous introductions to different parts of the slave coasts 

 and on numerous occasions. In fact the groundnut must have soon 

 become established, for it was first introduced to Jamaica from the 

 Guinea coast. The amazing thing about these American introduc- 

 tions is the rapidity with which they spread throughout the con- 

 tinent and the way the people adapted them to their methods of 

 cultivation. • 



