THE SELF-FERTILIZATION OF PLANTS. 391 



fallacies. By introducing the remark, that the grafting 

 acts powerfully on the reproductive system, he wishes 

 to insinuate the idea that the phenomena incident to 

 grafting, are not inconsistent with the view he pre- 

 viously propounded, to wit, that the good from cross- 

 ing is due to some peculiarity in the sexual constitu- 

 tion. The fallacy lies in this, that in either of his two 

 propositions, cause and effect are transposed, when 

 compared with the relation the good effects and their 

 cause bore to each other in the other proposition. His 

 first proposition is to the effect that some peculiarity 

 in the sexual constitution is the cause, and the good 

 observed is the effect. His latter proposition, however, 

 is to the effect that the good observed is the cause, 

 and the peculiarity in the sexual constitution is the 

 effect ! 



On page 437, Vol. ii., Animals and Plants, &c, he 

 speaks of the " facts which render it, to a certain degree 

 probable, that when the tissues of two plants, belong- 

 ing to distinct varieties, are intimately united," in Graft- 

 ing, " the characters of the two forms are united." 



On page 180, Vol. ii, Animals and Plants, &c, he 

 gives many instances of the good derived from Grafting. 



It is a matter, of supreme consequence, to understand 

 the reason of the lessened fertility, and of the sterility, 

 among individuals of the same species ; for, it is by the 

 test of sterility, that botanists determine what are and 

 what are not species. Where this is not the test, with 

 them, structural difference is ; and the consequence has 

 been, that the classification of species of plants is most 

 absurd. How can they safely make sterility, per se, a 



