Its Origin , Migrations , and Evolutionary Tendencies. 2 r 7 
higher altitudes there is an admixture of temperate species of Poa, Festuca , 
&c., but all the eastern grassveld remains on the whole subtropical. 
Mixed with the grasses throughout there are enormous numbers 
of herbaceous or shrubby species. The ‘ autumnal aspect societies which 
tend to replace the grasses, are again tropical in their affinities. On the 
other hand, the great mass of ‘ vernal aspect societies which are bulbous 
or geophytic as a rule in their growth forms, belong to such families as the 
Compositae, Papilionaceae, Geraniaceae, Asclepiadaceae, Liliaceae, Amaryl- 
lidaceae, Iridaceae, and, while constituting a special type of their own, the 
species being largely endemic, they have closer affinities with the temperate 
flora than with the tropical. They or allied species may occur on the 
mountains and elevated grassy plateaux of the tropics, but they are not 
characteristic of the tropical forest regions. 
It is interesting to note that these vernal aspect societies are charac- 
teristic of early stages of the plant succession, being gradually suppressed as 
succession advances. I have pointed out elsewhere that in a subtropical 
region, as succession advances, the vegetation tends to become more and 
more tropical, e. g. on the Natal coast-belt (3). 
The Temperate or Mountain Flora: Migration along 
Mountain Ranges. 
Reference once more to a physical map of Africa will show that the 
whole eastern side is a region of elevation. Some of the river valleys, 
e. g. the Zambesi and Limpopo, have cut rather far back through the moun- 
tain escarpment of the inland plateau, but otherwise highly elevated land is 
continuous from Abyssinia to the Drakensberg and westward across the 
southern end of South Africa to the Cape Peninsula. The south-western 
region of the Cape with its winter rainfall and dry summers has a ‘ Mediter- 
ranean flora ’ of warm temperate rather than tropical affinities. This 
temperate flora at increasingly high altitudes is continued eastward through 
the Drakensberg in Natal and the Transvaal and northward through 
Central Africa to Abyssinia. It is not only distinct ecologically but also 
floristically from that of the tropics and subtropical eastern side. 
The Compositae, Ericaceae, Proteaceae, Rosaceae (Cliff ortia), Gerania- 
ceae (Pelargonium), bulbous Monocotyledons, and many distinctive sections 
or genera in other families are most prominent in this mountain flora. The 
absence or rarity of such families as Acanthaceae, Capparidaceae, Anona- 
ceae, Menispermaceae, the majority of the Euphorbiaceae, large sections of 
the Leguminosae, the Sapindaceae, Melianthaceae, Sapotaceae, Cucurbitaceae, 
and many others so prominent on the coast-belt is equally striking. The 
majority of the species of the temperate or mountain flora are either herba- 
ceous or low-growing shrubs often gnarled and twisted. Mountain regions 
are regions of unstable topography and variable climatic conditions. Some 
