The Distribution of Species in New Zealand. 
BY 
J. C. WILLIS, M.A., Sc.D. 
With a Diagram in the Text. 
I N two recent papers 1 I have dealt with the distribution of angiospermous 
species in Ceylon, and have endeavoured to show that it follows simple 
arithmetical rules, whether one is dealing with the endemic species or with 
those more widely distributed. From Trimen’s figures for the local dis- 
tribution of the flora, which are very full and accurate, I have shown that 
both ‘ wides ’ (as for brevity’s sake I term the widely distributed species) 
and endemics are arranged in graduated series, the former being most 
numerous at the ‘very common ’ 2 end of the scale, the latter at the ‘very 
rare ’ 3 end. In both cases the numbers decrease towards the other end 
of the scale, i. e. they decrease in opposite directions. 
Not only do the grand totals show these graduated results, but each 
family and genus of reasonable size shows the same, and so do the smaller 
genera and families when added together into small groups. From this fact 
of the exactly similar behaviour of all groups I have drawn the conclusion 
that natural selection cannot be responsible for the actual distribution. 
Being of differentiating nature, it could not make all the plants behave 
alike. 
In the papers referred to I have, shown that if the flora of Ceylon 
be divided into three groups — endemic species, those confined to Ceylon 
and Peninsular India, and those with wider distribution than this — the first 
are the rarest, the second next most rare, and the last the commonest, rare 
in this connexion being understood to mean occupying less area. Accept- 
ing then the view that the wides are the oldest in Ceylon , 4 as well as the 
commonest, while the endemics are the youngest and rarest, the Ceylon- 
Indian species intermediate in both respects, I have deduced the conclusion 
1 The Endemic Flora of Ceylon. Phil. Trans., B, vol. ccvi, 1915, p. 307. The Evolution of 
Species in Ceylon, with reference to the dying out of Species. Ann. of Bot., vol. xxx, 1916, p. 1. 
2 Widely distributed in Ceylon. 3 Strictly local in Ceylon. 
4 In the present and preceding papers I have given a good deal of evidence in favour of this 
view, but in a subsequent paper I propose to put it all together in one piece, as this appears to be 
a view which is unacceptable to many. 
[Annals of Botany, Vol. XXX. No. CXIX. July, 1916.] 
