The South-east African Flora: Its Origin, Migrations, 
and Evolutionary Tendencies. 
BY 
J. W. BEWS, M.A., D.Sc., 
Professor of Botany in the Natal University College. 
Introduction. 
F EW regions are more favourably situated than South-east Africa for 
the study of plant distribution and its bearing on questions of evolu- 
tionary history. It is being recognized that one of the main problems 
in connexion with the phylogeny of the Angiosperms is the relationship 
between the tropical, subtropical, and temperate floras as well as the origin 
of various ecological types. Now in South-east Africa within a com- 
paratively small area there occur (i) a purely tropical flora, which is a 
southerly extension of the tropical flora of Central Africa on the coast-belt ; 
(2) a derived subtropical flora, adapted to drier and cooler climates, which 
becomes increasingly prominent towards the south on the coast-belt and 
occupies most of the region of rising altitude (1,500 feet and upwards) away 
from the sea ; and (3) a mountain or temperate flora, which occupies the 
higher altitudes (8,ooo ft. and over it) on the Drakensberg and other moun- 
tain ranges, descends to sea-level in the south-western region of the Cape, 
and connects through the mountains of Central Africa with the temperate 
flora of the Northern Hemisphere. The relationship between the first two 
types is very close. The purely tropical species are in a very large number 
of cases closely allied to the frost-resisting or more xerophytic subtropical 
species, and the tropical -subtropical vegetation may be grouped together as 
one element of the South African flora. The various modifications of it in 
reaction to changed ecological conditions, e. g. succulence, spinescence, and 
other forms of xerophytism, herbaceous growth- forms with capsular fruits 
and many other types, afford abundant opportunity for one line of research. 
A comparison of the coast-belt species with their nearest allies in the mid- 
lands of Natal from the morphological and physiological standpoints is 
in progress, and the results already obtained are extremely interesting. 
The temperate or mountain flora is a very distinct element. Of course 
it mixes to a certain extent with the tropical -subtropical element, but, in the 
[Annals of Botany, Vol. XXXVI. No. CXLII. April, 1922.] 
