164 DARAVmiSM chap. 



animals, and presumably from the same cause, too close inter- 

 breeding. 



Dean Herbert, avIio carried on experiments vnth great care 

 and skill for many years, found numerous cases of hybrids 

 which were perfectly fertile inter se. Crinum capense, fertilised 

 hj three other species — C. pedunculatum, C. canaliculatum, or 

 C. clefixum — all very distinct from it, produced perfectly 

 fertile hybrids ; while other species less difterent in appearance 

 were quite sterile with the same C. capense. 



All the s^iecies of the genus HipjDeastrum produce hybrid 

 offspring Avhich are invariably fertile. Lobelia syphylitica and 

 L. fulgens, two very distinct species, have produced a hybrid 

 which has been named Lobelia speciosa, and which I'eproduces 

 itself abundantly. Many of the beautiful jDclargoniums of 

 our greenhouses are hybrids, such as P. ignescens from a cross 

 Ijetween P. citrinodorum and P. fulgidu.m, which is quite 

 fertile, and has l^ecome the parent of innumerable varieties of 

 beautiful plants. All the varied species of Calceolaria, how- 

 ever different in appearance, intermix with the greatest readi- 

 ness, and the hybrids are all more or less fertile. But the 

 most remarkable case is that of two species of Petunia, of which 

 Dean Herbert says : "It is very remarkable that, although 

 there is a great difference in the form of the flower, esj^ecially 

 of the tube, of P. nyctanigenjieflora and P. phoenicea the 

 mules between them are not only fertile, but I have found 

 them seed much more freely Avith me than either parent. 

 .... From a pod of the above-mentioned mule, to which 

 no pollen but its own had access, I had a large batch of seed- 

 lings in Avhich there Avas no vaiiability or difference from 

 itself ; and it is evident that the mule planted by itself, in a 

 congenial climate, would reproduce itself as a species ; at least 

 as much deserving to be so considered as the various Calceo- 

 larias of different districts of South America."^ 



Darwin was informed by Mi\ C. Noble that he raises stocks 

 for grafting from a hybrid between Rhododendron ponticum 

 and E. catawbiense, and that this hybrid seeds as freely as it 

 is possible to imagine. He adds that horticulturists raise 

 large beds of the same hybrid, and such alone are fairly 

 treated ; for, by insect agency, the several individuals are freely 



^ AmaryllidacecE, by tlie Hon. and Rev. William Herbert, p. 379. 



