292 
Bews. — Plant Succession and 
ment of forest in the Drakensberg (4), extends from Natal to the Cape. 
The most important pioneer trees and shrubs iii Natal are included in the 
following list, which very nearly exhausts all those common to the Cape 
Peninsula and Natal : Rhus villosa , R. pyroides , R. lucida , Cunonia capen- 
sts, Olinia cymosa , Side roxy Ion inerme , Royena lucida , Celastrus buxifolius , 
C. acuminatus, Myrsine africana , Olca verrucosa , Celtis rhamnifolia, 
Kiggelaria africana , Scolopia mundii , Grewia occidentalism Noltea africana , 
Cliff ortia strobilifera, Psoralea pinnata , Plectronia vent os a, Halleria lucida . 
Myrsine melanophleos is a forest tree which, though it can withstand 
shade, also often acts as a pioneer, being rather widely adaptable. 
There are a few light-demanding climbers which extend from the 
Cape to Natal, e. g. Clematis brachiata, Scutia indicam Vitis capensis , 
Asparagus africanam A. aethiopieus, A. medioloides ; and a few parasitic 
species have the same wide distribution, e. g. Cassytha capensism Harveya 
coccincam H. purpurea, H. squamosa, H. bolusii , Melasma sessilijlormnm 
Thesium spRatum, Viscum obscurum. The wide distribution of these latter 
is not easy to explain either on ecological lines or by the age and area rule, 
for presumably they are younger than their hosts. 
It is interesting to find that the species which commonly take posses- 
sion after fire, e. g. Rubus pinnatusm Polygala myrtifoliam P. virgatam are 
again widespread types. They represent once more the initial stages 
of subseres. 
The result of this comparison of widespread species in South Africa 
appears to be that while they are seen to belong to widely different growth 
forms, and to show no possible phylogenetic relationship, yet with very few 
exceptions they agree in belonging to early stages of the plant succession. 
They act as pioneers which colonize either waste land or cultivated fields, or 
burnt-out forest, or they invade lakes and pools and vleis, or they colonize 
sand-dunes and open sea-shore habitats, or they belong to early stages of 
the main xerosere, and often play an important part in the establishing 
of grassland, or forest plant communities. The results, then, appear to 
justify the putting forward of the following hypothesis : 
Species with a zvide distribution are usually found in an early stage 
of the plant succession , 
The rule probably only applies to countries where there are great 
variations in climatic conditions, such as is the case in South Africa, where 
the climax types in drier parts so often represent the initial stages of 
succession in moister regions. This result is not to be considered as in any 
way contradictory to the age and area law already discussed. It is rather 
an ecological amplification of that law, and it is bound up with other 
principles of plant succession. 
Succession as a rule proceeds from extremes, where there is either too 
much or too little water, towards the mesophytic., and the highest stage of 
