LUTHER BURBANK 



been accepted, there was wide diversity of opinion 

 as to many of its important details. It could 

 scarcely be said that there was any prevalent doc- 

 trine as to what forces in nature caused the ob- 

 served variation between wild forms of plant and 

 animal life upon which the operation of natural 

 selection is based. 



The "survival of the fittest" was an accepted 

 doctrine, but the origin of the fittest was an un- 

 solved enigma. 



A suggestion that new forms might arise by 

 hybridizing existing species had occurred, doubt- 

 less, to many minds. But this idea was combated 

 or annulled by the prevalent notion that the off- 

 spring of true species are necessarily infertile. 



It is true that a few plant breeders, notably 

 Dean Herbert and Andrew Knight, had advocated 

 the idea that hybrids between true species may be 

 fertile, and, indeed, had even seemed to demon- 

 strate the truth of this view some three genera- 

 tions earlier. But the influence of the celebrated 

 experimenter, Carl Friedrich von Gaertner, had 

 served to give vogue to the opposite opinion. 



Darwin had argued for the fertility of some 

 natural hybrids, but he had not been able to make 

 out a case that by any means carried conviction 

 to the generality of biologists and botanists; and 

 the current opinion was that the comparatively 



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