424 GRAFT-HYBRIDS. Chap. XL 



peciiHcirities. But we should bear in miu.d that in all the 

 varieties of the potato, the tubers differ much more than any 

 other part. 



The potato affords the best evidence of the possibility of 

 the formation of graft-hybrids, but we must not overlook the 

 account given of the origin of the famous Cyiisus adami by 

 M. Adam, who had no conceivable motive for deception, and 

 the exactly parallel account of the origin of the Bizzarria 

 orange, namely by graft-hybridisation. Nor must the cases 

 be undervalued in which different varieties or species of vines, 

 hyacinths and roses, have been grafted together, and have 

 yielded intermediate forms. It is evident that graft-hybrids 

 can be made much more easily with some plants, as the 

 potato, than with others, for instance our common fruit trees ; 

 for these latter have been grafted by the million during many 

 centuries, and though the graft is often slightly affected, it 

 is very doubtful whether this may not be accounted for, merely 

 by a more or less free supply of nutriment. Nevertheless, 

 the cases above given seem to me to prove that under certain 

 unknown conditions ^raft-hybridisation can be effected. 



Herr Magnus asserts with much truth that graft-hybrids 

 resemble in all respects seminal hybrids, including their 

 great diversity of character. There is, however, a partial 

 exception, inasmuch as the characters of the two parent forms 

 are not often homogeneously blended together in graft-hybrids. 

 They much more commonly appear in a segregated condition, 

 — that is, in segments either at first, or subsequently 

 ^through i-eversion. It would seem that the reproductive 

 elements are not so completely blended by grafting as by 

 sexual generation. But segregation of this kind occurs by no 

 means rarely, as will be immediately shown, in seminal 

 hybrids. Finally it must, I think, be admitted that we learn 

 from the foregoing cases a highly important physiological fact, 

 namely, that the elements that go to the production of a new 

 being, are not necessarily formed by the male and female organs. 

 They are present in the cellular tissue in such a state that they 

 can unite without the aid of the sexual organs, and thus give 

 rise to a new bud partaking of the characters of the two 

 parent-forms. 



