295 
Plant Distribution in South Africa . 
monospord) are among the number. A very large proportion of the total 
number of species, however, are geophytic herbaceous forms, which are 
scattered among the grasses of the grassveld, and next to nothing is really 
known about their distribution. Many of them are certainly widely dis- 
tributed, e. g. those named in my work already referred to, but these also 
obey the general rule given above, for they are vernal plants and increase 
when the plant succession is sent back by grass burning or overstocking, 
i. e. they belong to an early stage of the succession. 
Over the whole dry interior, the Karroo, the sand veld, and the 
western regions, the vegetation is mostly of a semi-open primitive type, 
and, though practically the whole of these great areas is insufficiently 
explored to enable any exact information to be given as to the distribution 
of the different species, yet many of them are at least known to be wide- 
spread, though at the same time they may be endemic. 
The south-western or Cape region, where the climax stage of the 
plant succession, except in a few forest areas, is Macchia, is of peculiar 
interest in many ways. The number of endemic species is extraordinarily 
high. Some of them range all over the region, others are very rare indeed, 
at least as far as is known, but again much more information is necessary 
before any very definite statement can be made. The climatic con- 
ditions over the area are on the whole fairly uniform, and interesting results 
should be obtainable by applying the age and area law to this region. 
So far I have confined my attention to South Africa, in this attempt 
to throw some further light on the question of plant distribution by apply- 
ing ecological, and particularly successional, principles. At present I do not 
propose to enter into further details with regard to South Africa, or to 
attempt to apply the same methods to other countries, though there is much 
information scattered through ecological literature which has a bearing 
on the question. Thus Smith, in his Presidential Address to the British 
Ecological Society (13), dealt, inter alia , with the reasons why some grasses 
are widely distributed in Britain. It is interesting to find that he laid 
stress on their possessing high powers of surviving critical periods, 
especially winter and drought, but certain colonizers he notes as being 
restricted in distribution. Of course it is not claimed, even for South 
Africa, that pioneer species are necessarily widespread, though widespread 
species usually appear early in the succession. The climate of Britain, too, 
is very uniform as compared with that of any part of South Africa, and 
where the ecological sorting out depends more on edaphic than on climatic 
conditions, it is uncertain whether my rule will apply. The important 
thing, however, seems to be that any widespread species must have the 
environmental conditions which suit it also widespread. Early species 
in the succession, which have to be adapted chiefly to the inorganic environ- 
mental factors, are more likely to find those conditions to which they are 
