BOTANY. 221 



A. Westerly Wet region, Niger-Congo ; very hot 

 with April to October rains and below 3,500 feet. 



B. Easterly Wet region, Zambesi and other 

 valleys ; very hot, with October to April rains, 

 below 3,500 feet. 



C. Central ridge which is above 3,500 feet and 

 fairly dry, with October to April rains. 



Of this last the following sub-districts are all 

 above 4,500 feet and are each occupied both by a 

 low-level flora, 4,500 to 6,600 feet, which is in a 

 fairly dry and warm climate, and a high-level flora 

 above 6,600 feet which has extremely wet and 

 rather cold conditions of life. 



1. Abyssinia. 2. Euwenzori. 3. Central Water- 

 shed. 6. Shire highlands. 8. Kenia. 9. Masai 

 highlands. 10. Kilimandjaro. 



When better known probably both (4) Stevenson 

 Road (including south-east Tanganyika), and (5) 

 Angola will be found also to contain a high-level 

 of the wet and cold-loving Alpine forms. (11) 

 Usambara is in the same condition. Of the two 

 remaining districts, the (7) Victoria region lies 

 between 3,900 and 4,500 feet and has rather a dif- 

 ferent rainfall, while (12) Somaliland and Taru is 

 a desert with extreme drought. 



The question remaining is therefore to know 

 how all this came about. Here we are met on the 

 threshold by a barrier at present insurmountable. 

 There is no definite knowledge of the condition of 

 Africa in miocene times. 



