12 THE ORIGIN OF SPECIES 



insured in each generation a cross with pollen from a 

 distinct flower, either from the same plant or from an- 

 other plant of the same hybrid nature. And thus, the 

 strange fact of an increase of fertility in the successive 

 generations of artificially fertilized hybrids, in contrast 

 with those spontaneously self-fertilized, may, as I be- 

 lieve, be accounted for by too close interbreeding having 

 been avoided. 



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

 most experienced 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 re- 

 sults 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 singu- 

 lar fact, namely, that individual plants of certain species 

 of Lobelia, Verbascum and Passiflora can easily be fer- 

 tilized by 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 



