M. Ch. Naudin on Hyhridity in Plants. 231 



but if, on the contrary, it be not admitted, they would be 

 perfectly inexplicable. 



Let us suppose in the Toadflax hybrid of the first genera- 

 tion, that disjunction takes place both in the anther and 

 contents of the ovary ; that some grains of pollen entirely 

 belong to the paternal species, others to that of the mother ; 

 that in others disjunction has not, or, at least, only just 

 commenced. Again, let us suppose that the ovules are, to 

 the same degree, separated both in the direction of the 

 male and female parent ; what will result when the pollen 

 tubes descend into the ovary to fertilise the ovules ? If 

 the tube of a pollen grain, which has returned to the male 

 parent, meet an ovule separated in the same direction, a 

 'perfectly legitimate fecundation will be produced, from which 

 will result a plant entirely returned to the paternal species. 

 A similar combination effected between a pollen grain and 

 ovule, both returned to the female parent, the product will 

 return in the same manner to the species of this last ; if, 

 on the contrary, combination is effected between an ovule 

 and pollen grain, separated in opposite directions, they will 

 perform a true crossed fecundation, like that which gave 

 origin to the hybrid itself ; and there will again result a 

 form intermediate between two specific types. The fer- 

 tilisation of an ovule non-separated, by a pollen grain 

 separated in either direction, would give a quadroon hybrid ; 

 and since disjunctions, as much in the pollen as in the 

 ovules, can take place in all degrees, every sort of possible 

 combination will result as chance may direct. We have 

 seen these multitudinous forms produced in the Toadflax 

 hybrids, and Petunia from the second generation. 



The retrogression of a hybrid in its course of return to 

 one of the parent species is also easily explained by this 

 hypothesis. I mentioned several examples when speaking 

 of the third generation of Linaria purpureo-vulgaris. Thus, 

 for example, among eighty plants sprung from an individual 

 of the second generation, which seemed to be entirely re- 

 turned to L. purpurea, fresh hybrids appeared, which came 

 back to the intermediate form of the first hybrid, and 

 other individuals still more sensibly approached to L. 

 vulgaris. The reason is, that the purple- flowered hybrid of 



