76 PRESIDENTIAL ADDRESS SECTION C. 



such conditions are peculiarly suited for the production of new 

 species is shown by the large number of endemics which occur here. 

 They are far in excess of any other part of Natal. They may be- 

 widespread along the range from north to south, but they do not 

 occur at lower altitudes. Species seem to migrate readily along 

 mountain ranges. This may be due also to the general environ- 

 mental instability. 



Plant Migration and the Affinities of the Natal Flora. 



An analysis of the flora of Natal, family by family, brings to- 

 light the fact that it consists of two main important elements: (1) 

 the Tropical and (2) the Temperate. The former might also be 

 termed the "coast element" and the latter the "mountain element." 

 The tropical element in the narrowest sense consists of species 

 which actually occur in the tropics to the North., About 34 per 

 cent, of the coastbelt flora is of this nature. From this purely 

 tropical element a much larger sub-tropical element has been 

 derived, including most of the species which are dominant over the 

 midlands. The sub-tropical element extends also into the Cape 

 Colony, though few real tropical species do so except as stragglers 

 in favoured localities. 



The purely tropical element is not confined to the coastbelt. 

 It is also found further inland in the main river valleys (see Mid- 

 land Dry A f alley Scrub described already). The species in this inland 

 tropical type are to a large extent distinct from those of the coast- 

 belt, as they are in the tropics to the North, but to a certain extent 

 there has been a migration inland, along the river valleys, of coast- 

 belt species, e.g., in the case of Dichrostachys nutans. 



The temperate element of the Natal flora, as already men- 

 tioned, is most characteristic of the mountains, particularly the 

 great Drakensberg, which connects through the Stormberg and 

 Karroo ranges with the South-Western Cape Colony and to the 

 north with the high tropical ranges, right across the Equator and 

 north to Abyssinia. The Macchia and Alpine vegetation of the 

 Drakensberg is not only very similar to that of the Cape, but it 

 is also in many ways closely connected with that of Kilimanjaro, 

 Kenia, etc. The Drakensberg forms part of what may be looked 

 upon as a great highway of migration from north to south or from 

 south to north. At altitudes of 8,000 feet and more, the enor- 

 mous numbers of Compositae, Ericaceae, Rosaceae (Cliffortia, 

 Leucosidea), various bulbous Monocotyledons, etc., is to be con- 

 trasted with the absence or great scarcity of such families as Acan- 

 thaceae, Amarantaceae, Euphorbiaceae, etc., which are so 

 abundant on the coastbelt. Tropical or sub-tropical species are, 

 however, common and often dominant on the foothills and lower 

 slopes of the Drakensberg below 8.000 feet. 



Within the limits of a single family, such as the Gramineae, 

 the same distinction may be drawn between Temperate and Tropical 

 elements. The genera Festuca, Poa, Avenastrum, Pentaschistis, 

 Danthonia are temperate in their affinities and are more or lessr 



