296 
Bens . — Plant Stic cession and 
suited widespread over any area, than those species which belong to com- 
plex climax plant communities, where the surrounding vegetation is the 
most important factor for any particular species. This is especially true for 
the very mixed forests of Natal or any other subtropical or tropical region. 
Willis, in his various papers, seldom refers to the ecological side of the 
question, but one or two of his statements are significant. Thus, in his 
Ceylon paper, he says ( 15 , p. 13), c The number and proportion of endemics 
are far greater in the wet south-western zone, i. e. in the broken hilly 
country of Ceylon, than in the flat and uniform dry country which 
surrounds it to the north-east and south-east ’, and of course he has already 
shown that endemics are relatively restricted in their distribution. The 
fact that they belong to the moister parts agrees very well with what 
happens in South Africa, but in the moister parts the highest stages of the 
plant succession are able to develop, and it is to these complex plant 
communities that the endemics and species with restricted distribution 
.belong. 
Again, in his first New Zealand paper ( 16 ), Willis’s figures show that in 
the Cyperaceae, a family which is fairly uniform in its ecological behaviour, 
since most of its members belong to early stages of the (hydrosere) plant 
succession, both endemics and wides are widely distributed. Willis ex- 
plains this by stating that the family is very old in New Zealand, but it can 
be equally well explained by the theory outlined above. 
Summary. 
1. Willis’s ‘age and area’ law is discussed, and in general accepted, 
but it is pointed out that it can only apply to regions where conditions are 
fairly uniform, and in South Africa, where climatic variations are extreme, 
its operation is greatly modified. 
2 . Species (320 in number) which are widely distributed over South. 
Africa are compared, and it is found that such species usually are found in 
an early stage of the plant succession. They include many ruderal species 
which colonize waste land, &c., many aquatic and marsh plants which 
belong to early stages of the hydrosere, and the remainder are nearly 
all xerophytic, light-demanding species, which belong to early stages 
of the xerosere, and are often important pioneers in the establishing of 
grassland, scrub, or forest plant communities. 
3. On the other hand, some strictly pioneer species are not widely 
distributed. In many cases this is probably due to the more stable plant 
communities acting as barriers and retarding the spread of the pioneers. 
4. Certain large classes of species with a restricted distribution in 
South Africa are shown to belong to climax plant communities such as the 
coast-belt forest of Natal, as well as other forests. Reference is made 
to work recently completed ( 9 ) in which it is shown that in a subtropical 
