LUTHER BURBANK 



of organic nature of a good deal of its orderly 

 character. 



And so it appears, so far as may be judged 

 from my experiments, that even when hybrids 

 between these divergent forms are produced, the 

 offspring are sterile, and the results of the hybridi- 

 zation are not perpetuated. 



Such, then, is the barrier that nature erects 

 in the interest of race preservation, between 

 species that have widely diverged. 



But, on the other hand, we have seen many 

 illustrations of the fact that when species a little 

 more closely related are hybridized, the result 

 may be not to produce sterility but to give added 

 virility to the offspring. 



We saw this illustrated, for example, when the 

 walnut of the eastern United States was crossed 

 with the black walnut of California. The hybrid 

 progeny not only showed tremendous individual 

 vitality, growing with great rapidity and to 

 enormous size, but they produced an altogether 

 extraordinary abundance of fertile fruit. 



The hybrid variety thus produced — named, it 

 will be recalled, the "Royal"— constitutes a new 

 race that can more than hold its own against the 

 parent forms. 



And the reason for this, seemingly, was that 

 the two species of walnut had not become suffi- 



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