100 THE METHOD OF DARWIN. 



on plants, guided, to a certain extent, by the 

 experience of breeders of animals, I became 

 convinced many years ago that it is a general 

 law of nature that flowers are adapted to be 

 crossed, at least occasionally, by pollen from 

 a distinct plant." It was a direct deduction 

 from his theory of natural selection that, since 

 they are adapted for cross-fertilization, cross- 

 fertilization must be advantageous to them. 

 Hence it was perfectly natural that he should 

 like to verify it. "It often occurred to me," 

 he said, "that it would be advisable to try 

 whether seedlings from cross-fertilized flowers 

 were in any way superior to those from self- 

 fertilized flowers. But as no instance was 

 known with animals of any evil appearing in 

 a single generation from the closest possible 

 interbreeding, that is, between brothers and 

 sisters, I thought that the same rule would 

 hold good with plants, and that it would be 

 necessary, at the sacrifice of too much time, to 

 self-fertilize and intercross plants during sev- 

 eral successive generations, in order to arrive 

 at any results. I ought to have reflected that 

 such elaborate provisions favoring cross-fertili- 

 zation as we see in innumerable plants would 

 not have been acquired for the sake of a dis- 

 tant and slight advantage, or of avoiding a 



