242 THE ORIGIN OF SPECIES 



generally be fertilized during each generation by pollen from the 

 same flower; and this would probably be injurious to their fertihty, 

 already lessened by their hybrid origin. I am strengthened in 

 this conviction by a remarkable statement repeatedly made by 

 Gartner, namely, that if even the less fertile hybrids be artificially 

 fertilized with hybrid pollen of the same kind, their fertility, not- 

 withstanding the frequent ill effects from manipulation, some- 

 times decidedly increases, and goes on increasing. Now, in the 

 process of artificial fertilization, pollen is as often taken by chance 

 (as I know from my own experience) from the anthers of another 

 flower, as from the anthers of the flower itself which is to be 

 fertilized; so that a cross between two flowers, though probably 

 often on the same plant, would be thus effected. Moreover, when- 

 ever complicated experiments are in progress, so careful an ob- 

 server as Gartner would have castrated his hybrids, and this 

 would have insured in each generation a cross with pollen from 

 a distinct flower, either from the same plant or from another plant 

 of the same hybrid nature. And thus, the strange fact of an in- 

 crease of fertility in the successive generations of artificially fer- 

 tilized hybrids, in contrast with those spontaneously self-fertilized, 

 may, as I believe, be accounted for by too close interbreeding 

 having been avoided. 



Now let us turn to the results arrived at by a third most ex- 

 perienced hybridizer, namely, the Hon. and Rev. W. Herbert. He 

 is as emphatic in his conclusion that some hybrids are perfectly 

 fertile — as fertile as the pure parent-species — as are Kolreuter 

 and Gartner that some degree of sterility between distinct species 

 is a universal law of nature. He experimented on some of the very 

 same species as did Gartner. The difference in their results may, I 

 think, be in part accounted for by Herbert's great horticultural 

 skill, and by his having hot-houses at his command. Of his many 

 important statements I will here give only a single one as an 

 example, namely, that "every ovule in a pod of Crinum capense 

 fertilized by C. revolutum produced a plant, which I never saw 

 to occur in a case of its natural fecundation." So that here we 

 have perfect, or even more than commonly perfect, fertility, in 

 a first cross between two distinct species. 



This case of the Crinum leads me to refer to a singular fact, 

 namely, that individual plants of certain species of Lobelia, Ver- 

 bascum, and Passiflora, can easily be fertilized by the pollen from 

 a distinct species, but not by pollen from the same plant, though 

 this pollen can be proved to be perfectly sound by fertilizing other 

 plants or species. In the genus Hippeastrum, in Corydalis, as 



