BOTANY l6l 



Rhodesia and reported to the Colonial Office on the use of air 

 photographs in botany and forestry (not published). Ecology 

 from the air has also been exploited by C. R. Robbins (1934); 

 although an air surveyor himself, he realizes the limitations of the 

 method, and has produced a valuable contribution. The official 

 ecologist in Northern Rhodesia, C. G. Trapnell, has obtained 

 valuable results working on the ground, and has also used air 

 photographs to advantage; his results are published as appendices 

 to the annual reports of the agricultural department for 1933 and 

 1934, and with J. N. Clothier (1937) he has published a detailed 

 account of the survey incorporating soil and vegetation maps. 

 These link up with that for Southern Rhodesia by Henkel. For 

 Nyasaland, Topham (1930) has considered the effects of agricul- 

 ture in relation to forests. 



Little has been published for Angola or Mozambique beyond 

 the systematic works referred to on page 155. Gossweiler has given 

 a short sketch of the botanical regions of Angola; and is also pre- 

 paring a very complete phyto-geographical map of Angola. 

 Burtt Davy (1931) has produced a brief account of the forest vege- 

 tation for the whole of this region. 



Central Tropics 



There is a considerable amount of literature bearing on the 

 ecology of Kenya and Uganda, but study has been seriously 

 hampered by the lack of a flora for the determination of species. 

 Most of the common weeds can only be determined by workers in 

 Africa to species which are manifestly composite, or even to genera. 

 The following work may be mentioned: Snowden (1933) has studied 

 altitudinal zonation on the Bufumbira volcanoes and the adjoin- 

 ing Kigezi district in Uganda. Burtt (1934) has carried out a 

 study of the same region, and several other writers have described 

 the altitudinal zonation of Ruwenzori, Elgon, Kenya, and other 

 mountains. Mildbraed's (1922) important account of the German 

 Central African Expedition of 1907-8 deals mainly with rain 

 forest, and Dawe (1906) has also studied the forest districts of 

 Uganda. J. W. Nicholson (1929), in considering the influence of 

 forests on climate and water-supply in Kenya, concludes that in 

 certain regions the total rainfall is likely to be affected by changes 



