364 SCIENCE IN AFRICA 



not be a profitable crop until the local peoples learn to drink it 

 themselves; there is in fact a growing internal trade in coffee 

 already established in the Gold Coast, and at the Njala agricul- 

 tural station in Sierra Leone trials of coffee are now in progress 

 with the same object in view. Coffee has been studied at the 

 agricultural station of Bingerville in the Ivory Coast, and R. Por- 

 teres (1934) has discussed a disease there which involves atrophy 

 of the flower. It is ascribed to deficiency of fertile elements in the 

 soil, but the best method of control has not yet been decided. 



The botanical studies on coffee carried out by the Dutch authori- 

 ties in Java, particularly in connection with vegetative propagation 

 and selection, will doubtless prove of value to Africa. 



Tea is a crop of growing importance in East Africa. As yet 

 there is no special headquarters for research, but it is proposed to 

 make a study of this crop particularly at the new Mlanje experi- 

 mental station in Nyasaland. The lines on which work will prob- 

 ably be carried out are described by Dr. W. Small (1932). Mr. 

 Hadlow (1934) has written a brief history of tea planting in that 

 colony. The importance of understanding the relationship be- 

 tween the plant and the soil is fully realized, and the subject has 

 been studied locally during the last few years in relation to both 

 coffee and tea. The alkalinity and acidity at various depths (pH 

 gradient) is the chief factor: thus coffee in suitable neutral soil 

 (from volcanic rocks) grows roots to ten feet depth, but in acid soils 

 only to a few inches. Tea on the other hand prefers acid soils, and 

 Dr. Harold H. Mann (1933), when reporting to the Tanganyika 

 Government on the prospects of tea growing, pointed out that a 

 considerable redistribution of tea and coffee plantations is re- 

 quired. The acid soil of the Usambara Highlands, for instance, 

 where coffee has been struggling for the last thirty years, is highly 

 suited to tea, but useless for arabica coffee unless grafted on robusta 

 stocks. 



An excellent piece of work by H. H. Storey and R. Leach 

 (1933), the plant pathologists at Amani and in Nyasaland res- 

 pectively, concerns the disease known as tea yellow-leaf or tea- 

 yellows, which has affected the crop in Nyasaland over wide areas, 

 and is of particular interest from the ecological point of view. The 

 general appearance of the disease was that of a fungal pest or a 



