242 ON THE ORIGIN OF SPECIES 



we need not be surprised at some difference in the 

 result. 



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

 species were invariably fertile when intercrossed. But 

 it seems to me 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, derived from hostile witnesses, who 

 in all other cases consider 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 fertilised thirteen flowers of the one with the 

 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 fertilisation is by so much 

 the less easy as their differences are greater. How far 

 these experiments may be trusted, I know not ; but the 

 forms experimentised on, are ranked by Sagaret, who 

 mainly founds his classification by the test of infertility, 

 as varieties. 



The following case is far more remarkable, and 

 seems at first quite incredible ; but it is the result of 

 an astonishing number of experiments made during 

 many years on nine species of Verbascum, by so good an 

 observer and so hostile a witness as Gartner : namely, 

 that yellow and white varieties of the same species of 



