23G DEGREES OF STERILITY. Cu.vp. VIII. 



ness of this almost universal belief among breeders. Hybrids 

 are seldom raised b}-- experimentalists in great numl)ers ; and 

 as the parent-species, or other allied hybrids, generally grow 

 in the same garden, the visits of insects must be carefully pre- 

 vented during the ilowering season: hence hyljrids will gener- 

 ally have to be fertilized during each generation by their own 

 individual pollen ; and this would probably be injurious to their 

 fertility, already lessened by their hybrid origin. I am strength- 

 ened in this conviction by a remarkable statement repeatedly 

 made by Giirtner, namely, that if even the less fertile hybrids 

 be artilicially fertilized with hybrid pollen of the same kind, 

 tlieir fertility, notwithstanding the frequent ill elFects from 

 manipulation, sometimes decidedly increases, and goes on in- 

 creasing. Now, in the process of ai'tilicial fertilization, pollen 

 is as often taken by chance (as I know from my own experi- 

 vncc) from the anthers of another tlower, as from the anthers 

 of the tlower itself which is to be fertilized ; so that a cross be- 

 tween two flowers, though probably often on the same plant, 

 would be thus etfected. Moreover, whenever complicated ex- 

 jieriments are in jirogress, so careful an observer as Gartner 

 would have castrated his hybrids, and this wovdd have insured 

 in each generation a cross with pollen from a distinct tlower, 

 either from the same plant or from another plant of the same 

 hj'brid nature. And thus the strange fact of an increase of 

 fertility in the successive generations of art tficicdhf -fertilized 

 hylirids, in contrast Avith 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 l)y a third most 

 experienced hybridizer, namely, the Hon. and Rev. W. Herbert. 

 He is as emphatic in his conclusion that some hybrids are per- 

 fectly fertile — as fertile as the pure parent-species — as are Kiil- 

 rcuter and Gartner that some degree of sterility between dis- 

 tinct species is a imiversal law of Nature. He experimented 

 on some of the very same species as did Gartner, The diflVr- 

 ence in their results may, I think, be in part accounted for by 

 Herliert'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 examjile, namcdy, that " every 

 ovule in a pod of Crinum capense fertilized by C. revolutuni 

 ])roduced a plant, which I never saw to occur in a case of its 

 natural fecundation." So that here wc have perfect, or even 

 more than commonly perfect, fertility in a first cross between 

 two distinct species. 



