262 HYBRIDISM. Chap. VIII. 



with different degrees of facility on the quince ; so do 

 different varieties of the apricot and peach on certain 

 varieties of the plum. 



As Gartner found that there was sometimes an innate 

 difference in different individuals of the same two spe- 

 cies in crossing ; so Sagaret believes this to be the case 

 with different individuals of the same two species in 

 being grafted together. As in reciprocal crosses, the 

 facility of effecting an union is often very far from 

 equal, so it sometimes is in grafting; the common 

 gooseberry, for instance, cannot be grafted on the cur- 

 rant, whereas the currant will take, though with diffi- 

 culty, on the gooseberry. 



We have seen that the sterility of hybrids, which 

 have their reproductive organs in an imperfect con- 

 dition, is a very different case from the difficulty of 

 uniting two pure species, which have their reproduc- 

 tive organs perfect ; yet these two distinct cases run 

 to a certain extent parallel. Something analogous 

 occurs in grafting ; for Thouin found that three species 

 of Kobinia, which seeded freely on their own roots, 

 and which could be grafted with no great difficulty 

 on another species, when thus grafted were rendered 

 barren. On the other hand, certain species of Sorbus, 

 when grafted on other species, yielded twice as much 

 fruit as when on their own roots. We are reminded by 

 this latter fact of the extraordinary case of Hippe- 

 astruni, Lobelia, &c, which seeded much more freely 

 when fertilised with the pollen of distinct species, than 

 when self-fertilised with their own pollen. 



We thus see, that although there is a clear and 

 fundamental difference between the mere adhesion of 

 grafted stocks, and the union of the male and female 

 elements in the act of reproduction, yet that there is a 

 rude degree of parallelism in the results of grafting and 



