8 HYBRIDISM. [Chap. IX. 



asserts that a hybrid from Calceolaria integrifolia and 

 plantaginea, species most widely dissimilar in general 

 habit, •'' reproduces itself as perfectly as if it had been a 

 natural species from the mountains of CliilL" I have 

 taken some pains to ascertain the degree of fertility of 

 some of the complex crosses of Ehododendrons, and I 

 am assured that many of them are perfectly fertile. 

 Mr. C. Noble, for instance, informs me that he raises 

 stocks for grafting from a hybrid between Ehod. 

 ponticum and catawbiense, and that this hybrid " seeds 

 as freely as it is possible to imagine." Had hybrids 

 when fairly treated, always gone on decreasing in fertility 

 in each successive generation, as Gartner believed to be 

 the case, the fact would have been notorious to nursery- 

 men. Horticulturists raise large beds of the same 

 hybrid, and such alone are faudy treated, for by insect 

 agency the several individuals are allowed to cross 

 freely with each other, and the injurious influence of 

 close interbreeding is thus prevented. Any one may 

 readily convince liimself of the efficiency of insect- 

 agency by examining the flowers of the more sterile 

 kinds of hybrid Rhododendrons, which produce no 

 pollen, for he will find on their stigmas plenty of pollen 

 brought from other flowers. 



In regard to animals, much fewer experiments have 

 been carefully tried than with plants. If our systematic 

 arrangements can be trusted, that is, if the genera of 

 animals are as distinct from each other as are the genera 

 of plants, then we may infer that animals more widely 

 distinct in the scale of nature can be crossed more 

 easily than in the case of plants ; but the hybrids 

 themselves are, I think, more sterile. It should, 

 however, be borne in mind that, owing to few animals 



