18 CONTACTS WITH DARWINISM I [ch. ii 



they are worldwide in their distribution, which must therefore 

 have gone on in early times. Has natural selection been gradually 

 diminishing in its effects? 



The characters given in the " family " list are very important in 

 the distinctions between families, but they also appear very 

 frequently in distinctions between tribes, less often between 

 allied genera, and still less often between two allied species. It is 

 evident, therefore, that they can be rapidly produced, and do not 

 necessarily need a long and gradual evolution from species up- 

 wards. It is difficult to see how this can be so, unless they can be 

 the subject of single sudden changes, which as they are usually 

 divergent is not difficult to imagine. 



It is very difficult to apply the Darwinian explanation, that 

 distribution is due to superior adaptation, to a genus like Senecio, 

 for most of its species are, compared to the genus, quite local. If 

 there be any marvellous adaptation, then, to account for the 

 enormous distribution, it must be generic, and no one has ever 

 been able to make even a suggestion as to what it may be, or 

 wherein it is shown. The generic characters are purely morpho- 

 logical, with less functional adaptation even than the specific. 



The writer, as personal assistant to that best and kindest of 

 men. Sir Francis Darwin, who had helped his father in so much of 

 his work, was, of course, brought up in the arcana of natural 

 selection, and accepted it with enthusiasm. His first research was 

 upon adaptational lines, but he was not satisfied with the adap- 

 tational explanation of things, and when soon afterwards, in 

 1896, he went to Ceylon to succeed Dr Trimen, his views under- 

 went a complete change. The leisure time of the first six years was 

 devoted to a detailed study in both Ceylon and India of that 

 remarkable family of water plants the Podostemaceae (51-55), 

 containing about forty genera with 160 species, found in all the 

 tropics, with overlap into cooler regions. All live upon the same 

 substratum of water-worn rock (or anything firm, like timber, 

 that may be caught in the rock) in rapidly flowing water. They 

 are annuals, flowering immediately that the spathe comes above 

 water in the dry season, and then dying. If accidentally laid bare 

 by an unusual fall of water in the vegetative season, they soon 

 die without flowering. All the food comes from the water, and 

 they have no competition for place, except among themselves. 

 Enormous quantities of minute seed are produced, which have no 

 adaptation at all (except in Farmeria) for clinging to their place 

 in the swift current. At most one in a thousand or two may be 



