44 CONTACTS WITH DARWINISM III [ch. v 



More than thirty years ago the writer published a paper upon 

 the distribution of the Dilleniaceae (72), in which he adopted the 

 notion that mutation might at times be so large that there might 

 appear in one step a new species, or perhaps even a new genus. 

 Intermediate stages were not considered to be necessary, though 

 it was pointed out that in one or two cases intermediate forms, 

 perhaps hybrids, were found living side by side. 



By that time the author had completely discarded the theory 

 of natural selection as the chief driving force in evolution, re- 

 garding it primarily as a means of getting rid, promptly, of 

 anything that was seriously unsuited to the conditions under 

 which it had to live. There was, of course, no definite reason why 

 selection should not at times, under favourable circumstances, 

 produce new forms, but it seemed unlikely that such production 

 was at all common, or that it should produce forms of specific 

 rank. It could not be looked upon as operative in regard to the 

 bulk of the morphological characters which show us that evolution 

 has gone on, and which in consequence have always tended to be 

 regarded as in some way showing progressive adaptation. The 

 author had also abandoned the idea that there was such wonderful 

 morphological or structural adaptation in the flowering plants. 

 Each, of course, must be fairly well suited to the place in which it 

 grew, for if it were not, natural selection would soon dispose of it ; 

 but that was all, in most cases. Real adaptation was largely 

 internal as was clearly indicated (1) by the enormous range of 

 many species without any serious morphological change from one 

 region, or one set of conditions, to another; (2) by the great 

 numbers of plants that were to be found in the same conditions 

 (as nearly as made but little difference) and yet showed such great 

 morphological differences that they could be classified into many 

 different families and genera, though they might all come into 

 one ecological category, like the Podostemaceae or the plants of 

 a moor or a sand dune. The common plants of a moor in Britain, 

 for example, include Betula, Calluna, Carex, Cornus, Empetrum, 

 Erica, Kobresia, Listera, Molinia, Nardus, Potentilla, Scirpus, 

 and Vaccinium, covering a great range of the flowering plants, as 

 can be seen at a glance. Another indication (3) was the great 

 numbers of species of one genus that might at times be found in 

 similar conditions, like Mesemhryanthemums in South Africa, 

 while single species of other genera ranged over great differences 

 in conditions. 



The structural differences that showed in plants to such an 



