358 SCIENCE IN AFRICA 



kilogrammes of selected seed were produced at the various experi- 

 ment stations and nurseries. Records of yields in different areas 

 are collected by agricultural officers and should lead to valuable 

 conclusions regarding the suitability of different soils. Research 

 is carried on at stations at Bambesa for the Uele region and Ganda- 

 jiha for the Sankuru. The work of these stations includes selection, 

 multiplication of selected seed, study of cultural methods, control 

 of degeneration and of plant diseases and experiments in the rota- 

 lion of food or other crops with cotton. At Bambesa the entomo- 

 logists have studied pink boll-worm, Dysdercus, Helopeltis, and jassids 

 and have established that 'shedding' is caused by a capsid bug 

 (TNEAC 1934, A.R.). At Gandajiha the U.4 type has been found 

 more satisfactory than local varieties. Studies on Helopeltis, the 

 cause of stem canker, have been published by R. Steyaert and 

 J. M. Vrydagh in 1933, and by the latter in 1936. Among other 

 pests of cotton Dysdercus has been discussed by A. Buxhe (1936), 

 and the pink bollworm by Vrydagh (1932), H. Bredo (1934 and 

 1936) and Mme. D. Soyer (1932). The two last-named have 

 considered particularly the effects of disinfection by heating.^ 



Sisal {Agave sisalana) is a product mainly of Eastern Africa. 

 Owing to its xerophytic character this plant can be grown in 

 areas such as the Tanga plains and the floor of the rift valley, 

 where the rainfall is not sufficient for other perennial crops such 

 as coffee or tea. In Mozambique, where sisal has recently become 

 one of the chief exports, production is confined mainly to the 

 central regions and the area north of the Zambesi. 



Sisal has been tried in some parts of West Africa, notably on the 

 comparatively dry Accra plains of the Gold Coast, where, how- 

 ever, though successfully grown, it could not be recommended for 

 native cultivation, owing to the high capital expenditure involved 

 in the extraction of the fibre. Exports of sisal from French West 

 Africa have increased in recent years; the principal centres of 

 production are in the Sudan, but it is grown also in Senegal, the 

 Ivory Coast, and Guinea. Considerable progress has been made 

 at Amani in breeding sisal and other species of fibre Agave, and 

 since the opening in 1934 of the new Sisal experimental station 

 at Mlingano in Tanganyika, material has been transferred there 



* See also Chapter X, p. 284. 



