M. Oil. Naudiu on Hyhridity in Plants. 233 



the two. In the latter case the hybrid posterity returns 

 entirely and exclusively to one only of the two producing 

 species. 



(6.) Are there any exceptions to the law of return of hybrids to the 

 parent forms? Do certain hybrids become fixed and give rise to 

 nevj species ? 



T have not been long enough engaged in the study of 

 hybrids to have formed any settled opinion on this question. 

 Many botanists of good authority believe that some hybrids, 

 if not all, can become fixed and pass to the state of constant 

 varieties, that is to say, true species, intermediate between 

 those of their parents ; this is in particular tlie opinion of 

 M. Eegel, who regards it as probable that in the group of 

 willows, roses, and many other genera rich in nearly allied 

 forms, the nomenclature of which is very embarrassing to 

 the botanist, there originally existed but a small number 

 of species (two or three), the fertile crossings of which have 

 given rise to equally fertile hybrids, which, in their turn, 

 crossing between themselves and their parents, have pro- 

 duced, age after age, those multitudes of forms which exist 

 at the present day. 



Such may be the case, but it is without proof, and the 

 hypothesis is entirely gratuitous. In my opinion the fact 

 may be explained otherwise in a much more natural and 

 probable manner, viz., by the inherent property of all 

 organisms (at least vegetable) to modify themselves to a 

 certain extent according to the influence of the surrounding 

 medium, in other words, by the innate tendency of what we 

 call species to subdivide into secondary species. How can 

 it be admitted, for example, that roses, which are dissemi- 

 nated over the whole extent of the Old World, from Ireland 

 to Kamschatka, from the Atlas and Himalayas to the 

 glacial ocean, which cover all North America, which are 

 often isolated in narrow spaces and different localities, can 

 have met each other to give rise to hybrid forms ? 



It would be hardly possible to conceive such a fact. 

 Have roses never been subjected to experiment to ascertain 

 how far they can mutually hybridise, and if their hybrids 



