Tult ENE ENSA ae aoe eT E S 
FROM THE STANDPOINT OF AN IDEALIST. 443 
geographical conditions opened to him a prospect of removing a serious 
difficulty that might have been fatal to the general theory ; and that was 
the difficulty of conceiving the early stages in the differentiation of a type 
in response to the first stages of the diversification of uniform conditions. 
Since characters become more constant and adaptivity to present conditions 
becomes less marked as one proceeds up the scale from the species to the 
family, it was obvious that if the hypothesis was to stand a different order of 
things had to be postulated for the development of the larger groups, an 
order of things in which instability of characters was associated with 
uniformity of conditions. The responses of our great family types to the 
changes in environment are negligible. Yet the distant age of the Creta- 
ceous that witnessed the deployment of the Angiosperms, much as we know 
them now, must have been preceded by an era of great instability of floral 
characters—characters on which the taxonomist has based his families and 
his groups of families, and characters that have been more or less fixed 
during the ages that have since elapsed. 
Obviously one was here face to face with a different order of things, but 
some time elapsed before further progress could be made in the elaboration of 
the theory. Having abandoned the position that uniformity of conditions and 
immutability of type went together, a position that was the logical sequence 
of the differentiation hypothesis as at first conceived, one had either to adopt 
the opposite view or throw over the theory. It was nota dilemma peculiar 
to the differentiation theory, since the mutationist and the Darwinian 
evolutionist experience a similar difficulty when they deal with the genesis 
of the larger groups, the development of the family requiring the instability 
of characters which are mainly constant under present conditions. The way 
out of the difficulty was suggested on reading the account by Dr. Willis 
of the extreme uniformity of conditions in which the Podostemacee and 
Tristichacez live in mountain-torrents and rushing streams around the 
tropics, a description of a state of things approaching the primeval state 
as far as uniformity is concerned. He describes the great morphological 
changes of the floral and vegetative organs under such conditions, modifica- 
tions characterized as without any adaptive significance and as the result of 
free mutation in every direction (Proc. Roy. Soc. vol. Ixxxvii. pp. 546, 548 ; 
1914). He speaks of “the most astonishing variety of morphological 
structure" under conditions of life “absolutely uniform " (bid. p. 533) 
On the results of the investigation of these families for many years he builds 
a powerful argument for the Mutation theory, and one can scarcely doubt 
that in time he will adopt a standpoint not essentially different from that of 
the Differentiation hypothesis. But what one is concerned with here is the 
association of extreme uniformity of conditions with extreme instability of 
type. It isa picture of the abnormal side of plant-life. 
In explanation of the remarkable mutations of the floral organs displayed 
