The Relative Age of Endemic Species and other 
Controversial Points. 
BV 
J. C. WILLIS, M.A., Sc.D. 
I N a recent number of this journal there is a paper by Mr. H. N. Ridley 
(1) in which he expresses great dissatisfaction with the hypothesis of 
‘ age and area ’ which I have elsewhere (5, 6, 7) brought forward as being, in 
my opinion, a general rule which has governed the distribution of the 
Angiosperms (and some animals at any rate) about the globe. Mr. Ridley 
also sets forth the case from the Natural Selection point of view ; for there is 
no doubt that the adoption of my hypothesis involves a final abandonment 
of Natural Selection as seriously operative in this direction. Whatever it 
may, and doubtless does, effect in individual cases, its results are not 
sufficiently marked to show themselves in my figures, which deal with large 
numbers and the long run, and are similar to one another for all groups of 
plants. Mr. Ridley’s paper was evidently written before seeing my subse- 
quent paper on the flora of New Zealand (7), or much that it contains 
might have been omitted, or left for further consideration. 
I shall take Mr. Ridley’s points, as given in his summary, in order, 
paying special attention to the supposition often brought forward, that 
endemics are chiefly the relics of an old flora ; and shall also give further 
evidence for my hypothesis, which if once fully accepted, will make a great 
difference in the handling of questions of geographical distribution and 
evolution at least, if not in other lines of work. 
In the earlier portion of his paper Mr. Ridley seems to me to imply 
that my numerical results are accidental. But, as I have already pointed 
out, the probabilities against such a thing are inconceivably great. In the 
first place we have to note the very remarkable fact that the same accident 
would appear to have happened to all, and we have now the further case of 
New Zealand, where instead of the estimates of the Ceylon flora I have used 
actual longitudinal range in the islands, and where every family and genus 
(for even the genera with one or two species follow the grouping as accurately 
as those with more, which are quoted in the tables) behaves in the same 
way. Ceylon is quite put into the shade by the way in which the flora of 
New Zealand follows my hypothesis. 
[Annals of Botany, Vol. XXXI. No. CXXII. April, 1917.] 
