2 l 2 
Agnes A r her. — On the Lctiv of Age and A rea, in 
palaeobotanical evidence which can scarcely be gainsaid. For the sake of 
brevity I will cite one instance only. Professor Berry, 1 by bringing together 
the evidence of Cretaceous and Tertiary fossils, has established that the 
genus Nelumbo, which is now represented by two species only, occurring 
respectively in Asia and America, had formerly a cosmopolitan range, 
including Greenland, Europe, and Africa. A number of the species which 
have been identified in the fossil state are now wholly extinct. A map 
showing the present and past distribution, which is included in Professor 
Berry’s paper, brings vividly home to the reader the losses which this genus 
has suffered. 
Having become convinced that Willis’s position, in regard to the extinc- 
tion of Angiospermic plants, was untenable, I sought to discover whether 
the validity of the Law of Age and Area must, in reality, stand or fall with 
the question of the dying out of species ; the conclusion I have reached is 
that Willis’s deductions regarding extinction depend upon a false assumption, 
and that they may be discarded without in any way affecting the truth of 
the law. 
It will be remembered that Willis bases his hypothesis in the first 
instance upon a consideration of the degree of rarity of the various species 
constituting the flora of Ceylon. 2 Following Trimen, he classifies the plants 
into a series of classes grading from ‘ Very Common ’ to ‘ Very Rare ’, and 
he uses the ingenious idea of awarding to each species ‘ marks ’ for rarity on 
a numerical scale. He writes, regarding the statistics based upon these 
classes, ‘ In what way the figures we have given are to be reconciled with 
any theory of the dying out of species I fail to understand ’. 3 When we 
scrutinize Willis’s degrees- of rarity more closely, we see that he uses the 
words ‘ common ’ and ‘ rare ’ in a slightly peculiar, 4 5 though legitimate, .sense, 
which he is careful expressly to define ; he lays special stress on the fact 
that ‘ my figures . . . refer to area occupied, not to commonness on the 
ground ’. 6 This being the case, it seems to me quite impossible to draw any 
conclusions for or against extinction from the figures in question ; the whole 
matter hinges upon a confusion of thought between ‘ common ’ in the sense of 
widespread, and i common ’ in the sense of numerically abundant. Willis 
apparently expects that those who differ from him on the question of 
extinction ought to be able to ‘ define a size of area above which species are 
to be regarded as growing, or below which as dying out’. 6 But what Tight 
have we to assume that the mechanism of extinction of a species is simply 
1 Berry, E. W. (1917 2 ). 2 Willis, J. C. (1915). 8 Willis, J. C. (1916). 
4 The contention that Willis uses the word ‘ common ’ in a sense unusual among naturalists, is 
supported by the fact that Darwin (Origin of Species, 6th ed., 1894, p. 40) defines the most common 
species as those that ‘ abound most in individuals ’, and also draws a distinction between ‘ wide 
range ’ and ‘ commonness 
5 Willis, J. C. (1917) (the italics are mine). 
Willis, J. C. (1918). 
