HYBRIDISM 43 



ditions, might be expected to produce varieties, which 

 would be little liable to have their reproductive powers 

 injuriously affected by the act of crossing with other 

 varieties which had originated in a like manner. 



I have as yet spoken as if the varieties of the same 

 species were invariably fertile when intercrossed. But it 

 is impossible to resist the evidence of the existence of 

 a certain amount of sterility in the few following cases, 

 which I will briefly abstract. The evidence is at least 

 as good as that from which we believe in the sterility 

 of a multitude of species. The evidence is, also, de- 

 rived from hostile witnesses, who in all other cases con- 

 sider fertility and sterility as safe criterions of specific 

 distinction, Gartner kept during several years a dwarf 

 kind of maize with yellow seeds, and a tall variety with 

 red seeds growing near each other in his garden; and 

 although these plants have separated sexes, they never 

 naturally crossed. He then fertilized thirteen flowers of 

 the one kind with pollen of the other; but only a single 

 head produced any seed, and this one head produced 

 only five grains. Manipulation in this case could not 

 have been injurious, as the plants have separated sexes. 

 No one, I believe, has suspected that these varieties of 

 maize are distinct species; and it is important to notice 

 that the hybrid plants thus raised were themselves 

 perfectly fertile; so that even Gartner did not venture to 

 consider the two varieties as specifically distinct. 



Girou de Buzareingues crossed three varieties of 

 gourd, which like the maize has separated sexes, and 

 he asserts that their mutual fertilization is by so much 

 the less easy as their diflerences are greater. How far 

 these experiments may be trusted I know not; but the 



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