BOTANY 171 



ment in thorn country and sweet bush grasslands, and concludes 

 that rotational grazing in paddocks and extensive mowing would 

 improve the veld and prolong the nutritive value of the natural 

 grass to such an extent that cultivated pasture would be unneces- 

 sary. H. B. Stent contributes valuable data on seasonal changes 

 in the chemical composition of pasture grasses. 



In Tanganyika the problems have been briefly stated by R. R. 

 Staples (1934), the pasture officer, and the annual reports of the 

 Department of Veterinary Science and Animal Husbandry for 

 1933, 1934, and 1935, have sections by him on pasture research 

 and also results of chemical analyses of grasses by M. H. French, 

 the biochemist. A reference herbarium for the difficult task of 

 identifying the local grasses is being collected by Capt. Hornby, 

 Director of the veterinary department, and Mrs. Hornby, with 

 the co-operation of the botanist at Amani. Introductions have 

 been made from South Africa, Southern Rhodesia, Australia, and 

 India, while grazing trials on acre paddocks of various indigenous 

 African grasses are in progress at Mpwapwa, the headquarters of 

 the veterinary department. 



Staples has recorded the grazing conditions in several districts 

 during the past few years, in order to gauge as accurately as possible 

 any vegetation changes in the pasture which may result from in- 

 creases in stock. Conditions in the Ngorongoro crater on the edge 

 of the Serengeti plains are of particular interest. Though little 

 more than one hundred square miles in extent, it is estimated to 

 carry upwards of eighty thousand head of game, besides some 

 twenty thousand Masai cattle for six months of the dry season. 

 All the kinds of game are maintained in excellent condition until 

 the very end of the dry season. As a pasture area the crater is of 

 special interest in that grazing seems to be the chief factor in main- 

 taining the dominance of the grasses. The astonishing carrying 

 capacity is partly due to fertile soil conditions, but above all to the 

 annual resting of the pastures when the game migrates in the wet 

 season, combined with heavy manuring by droppings. It is there- 

 fore a valuable natural demonstration of the benefits of resting and 

 manuring pastures. In Tanganyika an inquiry is also going for- 

 ward regarding the transpiration rates of plants, since local indica- 

 tions suggest that in the conservation of water-supplies it may be 



