CHAPTER VI 



THE PALAEOTROPICS 



AFRICA AND CONTINENTAL ASIA 



As we have already seen, the tropical floras of the two hemi- 

 spheres differ far more from each other, than do those of the 

 boreal zones. 



In the eastern hemisphere (Palaeotropics), there are two 

 distinct floras, the African and Indo-Malayan, which occupy 

 widely separated regions, and are very different from each other. 

 The American tropics (Neotropics), form a single geographical 

 unit, and the flora is much more homogeneous. 



Tropical Africa 



Much the greater part of Africa lies within the tropics, the 

 Tropic of Cancer passing through the centre of the Sahara, while 

 the Tropic of Capricorn lies only about 12° north of the Cape of 

 Good Hope. In spite of the latitude, however, only a relatively 

 small part of Africa exhibits the climatic conditions usually 

 associated with the tropics. 



The topography of the great African continent is peculiar. 

 For the most part there is a gradual rise from the coast, sometimes 

 in broad terraces, to a great central plateau, with relatively little 

 land at sea-level. This is less marked in the equatorial regions of 

 the West Coast where there is a development of the rank forest 

 growth characteristic of the wet tropics, not shown to any greal 

 extent elsewhere in Africa. 



While the greater part of the continent consists of table lands. 

 the elevation of these is moderate (1,000—2,000 metres), and the 

 high mountains, like Kilimanjaro and the great Kamerun, are 

 generally more or less isolated masses rising from the much lower 



table land. 



This elevation of the general mass of the continenl of course 

 involves a decided lowering of the mean temperature of the plateau 



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