494 
Willis. — Endemic Genera of 
which they might have been supposed to have evolved. Not only so, but 
such spots were frequently to be found with no local species upon them. 
Only about a quarter of the whole number were confined to single spots, 
and more than half of those were restricted to the tops of single moun- 
tains (12). The remaining three-quarters occupied areas of larger and 
larger size, and in diminishing numbers as one went up the scale. The 
three diagrams here reproduced give the ranges of the species in half of 
vol. i of Trimen’s ‘Flora’, belonging to the three lowest of the six classes 
according to range into which he divided them. The VR (very rare) 
species are as a rule well localized, but the R (rare) and RR (rather rare), it 
will at once be observed, cover areas that overlap one another like the rings 
Diagram i. Distribution in Ceylon of the earlier VR, R, and RR species from Trimen’s ‘Flora ’. . 
in a shirt of chain-mail. Now a little consideration will soon show that 
from the point of view of evolution to suit local conditions this is a very 
remarkable state of affairs. 1 If A and B grow in overlapping areas, both 
must be growing in the coincident portion, and what keeps A from growing 
into the rest of B’s territory, B into A’s ? In reality the case is more 
complex, for if all the species were entered, there would be at least a dozen 
overlapping at any one point. It is all but inconceivable that local adapta- 
tion should be so minute as this, with soil essentially the same throughout, 
and the rainfall, &c., varying much from year to year. The species would 
have to be adapted to wide range in rainfall, and to very slight in a combina- 
tion of other factors. It was clear that the old ideas of particular adapta- 
tion were quite untenable. 
1 It is of course obvious that if a species newly evolved does not suit local conditions it will not 
survive, but this is a different point of view from supposing it evolved to suit them. 
