19 2 Wtllzs . — The Relative Age of Endemic 
Mr. Ridley does not fully realize that my figures, though it is definitely 
so stated in several places, refer to area occupied, not to commonness on the 
ground. On p. 552 he quotes the two Hedychiums as instances of VC 
species which have now died out at Peradeniya, showing a lack of 
apprehension of the real drift of my argument. To begin with, he quotes 
them both as VC, but if he will take the trouble to look again at Trimen's 
Flora, he will see that this is not quite correct. In the second place, it is not 
difficult to find them near Peradeniya, though not perhaps on the Kandy 
road, which is now practically a suburban street. The area occupied by 
these species remains as before, though evidently the operations of man have 
reduced their commonness within that area. But even if they were non- 
existent now in the places where man has introduced a change of conditions, 
that would not in any way affect my argument, which refers to action under 
constant conditions. The incoming of man may easily produce as great 
changes as a change of climate or other geological change, and I much regret 
that in my earlier statements of the law I did not lay more stress upon the 
many conditions that may modify its action, as for example by the use of 
such a covering phrase as ‘so long as conditions remain unaltered’, but 
somehow this seemed to me so obvious that it was unnecessary. If a power- 
ful magnet be placed near to the line of fall, it is obvious that an iron ball 
will not fall in exact accord with the law of gravity, but that fact does not 
alter the validity of the law. 
We may therefore dismiss from further consideration here all such 
cases as are brought up by Mr. Ridley showing the effects of man’s action 
in the spread of species, or in their destruction, and go on to a further 
objection raised against the species which Trimen labels VC. Mr. Ridley 
would apparently regard most of these as also introduced by man. This is, 
I think, somewhat sweeping. In my Catalogue I have marked by an 
asterisk those which Trimen or I think to have been possibly or probably so 
introduced, and they number 52 out of 285, showing rarities VC 12, C 25, 
RC 5, RR 2, R 4, VR 4, giving a mean rarity of 2-4. Subtraction of all 
of them makes no difference at all in my figures. But in order to satisfy 
Mr. Ridley, let us omit all the 285 VC’s, thus reducing the flora to five classes. 
Instead of 809 endemics with 3,518 marks, we get 790 with 2,709 ; instead 
of 492 Ceylon-Indians with 1,714 marks, we get 447 with 1,222, and instead 
of 1,508 wides with 4,579 marks, we get 1,287 with 3,071. These, calculated 
out, give rarities of 3-4, 2-7, and 2*3, in figures running from 1 to / only. 
These are just as useful for my deductions as those actually employed, and 
the omission of the whole 285 VC species makes no important difference. 
The same remarks as have been made upon the effects of the action of 
man apply to the effects of a change of climate, which in my New Zealand 
paper, p. 456, I mentioned as one of the factors causing modification. It is 
obvious that if a serious change of climate occurs — usually in consequence 
