•210 A NATURALIST IN MID-AFRICA. 



in marking out floral regions is a knowledge of the 

 facts connected with the beginning and duration 

 of the hot and rainy seasons. These will be found 

 at greater length in the preceding chapter. Our 

 knowledge of these simple facts in Central Africa 

 is chaotic as compared with our knowledge of the 

 plants of different regions. 



I am not going to subdivide Africa into a large 

 number of divisions. There is a German paper by 

 Dr. Buchwald, in which the continent is divided 

 into 38 districts, each of which is subdivided, so 

 that there are in all 109 subdivisions marked by 

 abbreviations. " B ' may stand for Berber, 

 Bongo, Baringo, Benue, Barombi, or Bachila, &c. 



The simplest way of grasping the facts, as I hold 

 them, is to start by imagining a subsidence of 3,500 

 feet all over the continent. If this took place the 

 Niger and Congo valley would be almost entirely 

 submerged. A ridge of high land, beginning in 

 Abyssinia and Lower Egypt, would pass due south 

 by Buwenzori and east of Tanganyika, and some- 

 where in the neighbourhood of the Stevenson 

 Road plateau would turn west along the water- 

 shed of the Congo and Zambesi to the sea in 

 Angola. The whole country to the west of this 

 would be submerged, except for little islands such 

 as the Cameroons and Kong mountains. This 

 submerged district is our first botanical region. 



The ridge — which is of course what I have 

 called the Central Watershed — or a branch of it, 



