BOTANY. 223 



excavations : The Niger and Congo valleys would 

 be occupied by the ancestral Coast Jungle Flora of 

 India which would rapidly multiply its species as 

 the valleys broadened and deepened, and finally 

 occupy, as they do now, the whole Niger-Congo 

 area, with pioneers in the valleys of Kuwenzori and 

 the Malagarasi. The Nile would deepen the Victoria 

 region and the steppe forms would colonise it. 



The Zambesi, Rovuma, and other rivers on the 

 east, are very insignificant as compared with the 

 Nile and Congo, and I think it is safer to assume 

 that they were colonised at a much later date 

 when the Coast Jungle Flora was nearer its 

 present condition. At any rate, it is simpler to 

 suppose that these valleys are inhabited by plants 

 whose ancestors came originally round the eastern 

 coast, via Zanzibar, and which now reach even as 

 far south as the coast of Natal. 



This may seem a gigantic and baseless specula- 

 tion, but I think it is possible. If true, it would 

 at any rate account for certain facts which are to 

 my mind absolutely proved, but cannot be ex- 

 plained on any other hypothesis ; namely, first, the 

 strange fundamental difference between the Niger- 

 Congo Soudan area, and the Zambesi and Zanzibar 

 district, and, secondly, the distribution of the 

 steppe flora and the Alpine flora. It may at 

 any rate be considered a working hypothesis ; 

 though ultimately it can only be tested by 

 increasing knowledge of the geological facts. 



