t 8 Bews. — Some General Principles of Plant Distribution as 
C. buxifolius is a widespread rather variable pioneer species all over South 
Africa, and is of considerable importance in the establishing of thorn-veld 
and scrub, though s%me of its more mesophytic varieties occur in the 
forest. C. peduncularis , which is without spines, is a large forest-tree 
common in eastern forests. C. acuminatus , like C. buxifolius , is widespread, 
usually outside but sometimes inside forest, and several other species behave 
in the same way. Some of the species have become adapted to coast sand- 
dune conditions, e. g. C. maritimus , or coast forests, e.%. C. cordatus. 
According to Sim’s information regarding distribution (31), C. undatus in 
forest and scrub would appear to take the place of the pioneer C. albatus , 
which is closely allied (31, p. 1 8(5) and occurs on exposed rocky krantzes. 
The relationship between the species of ElaCodendron is exactly the 
same as in the case of Celastrus and other large genera of trees and shrubs. 
A number of species are light-demandingpioneers, low-growing and shrubby, 
while others, like E. croceum (Saffron Wood) or E . sphaerophylhnn , are large 
mesophytic forest-trees. 
Ampelideae. 
The numerous species of Vitis ( Cissus ) are nearly all eastern, V. capensis 
being the only species which reaches the Cape Peninsula, though several 
others reach the eastern parts of the south-western region. The head- 
quarters of the genus is, of course, in the tropics, and again various steps of 
invasion into South Africa can be studied, as can be done also with members 
of the family Sapindaceae ; but a still better field is afforded by the next 
example. 
A nacardiaceae. 
The genus Rhus illustrates better our various principles than probably 
any other genus, and it deserves further study from this as well as other 
standpoints. Not only is the genus very well represented in South Africa, 
but it extends through tropical Africa, North Africa, the Mediterranean, 
Arabia, India, the Himalayas, China, North America, Mexico. Schonland 
(29) says about it, ‘ No less than eleven species occur on the Cape Peninsula 
alone, yet the close analysis to which the sect. Gerontogeae , Engl., which 
includes our own species of Rktts, has been subjected by Diels, leads him, 
and I think rightly, to the conclusion that this section has branched from 
the type ( stamm ) of the genus, presumably during early Tertiary in the 
southern portion of the eastern part of the northern hemisphere. Originally 
it probably included forms the organization of which was adapted to 
moderately dry and sunny localities. When, in the course of the Neogene, 
the geological revolutions in western Asia and Europe caused migrations on 
a large scale, and at the same time more intimate relations were established 
between East Africa and the Indian region, Rims took part in the general 
invasion of Eurasian types into Africa and there commenced in numerous 
regions a more diverse development than in its original home.’ 
