PLANT AFFINITIES 



In response to a further query, I named for 

 my visitor, among plants that often hybridize in 

 a state of nature, the various species of the genus 

 Rubus, including the blackberry, raspberry, the 

 tribe of wild roses and crabapples; the California 

 lilac, the various members of the oak tribe, the 

 willow, the strawberry and the huckleberry; nor 

 are these all the list might be almost indefinitely 

 extended. 



Indeed, it is my firm conviction that hybrid- 

 izing between natural species is a phenomenon of 

 almost universal occurrence. 



I believe that no other equally plausible 

 explanation has been given of the appearance 

 of seeming spontaneous varieties or mutations 

 that furnish the material for the operation of 

 natural selection, and are thus the basis of 

 organic evolution. 



It is true that such a suggestion as this 

 would have seemed heretical not very long ago; 

 but vast numbers of experiments in hybridizing 

 different species, and even representatives of 

 different genera, in my orchards and gardens 

 have afforded a mass of evidence that no one 

 can ignore. So to-day it is coming to be recognized 

 more and more generally that the hybridizing of 

 wild species is Nature's conventional method of 

 producing variability, and, as it were, testing out 



[35] 



