80 TRANSACTIONS OF THE ILLINOIS 



would be impossible to keep true by present methods any variety o£ 

 fruit by grafting or budding. The thousands of seedling stocks on. 

 which the Yellow Bellflower variety has been grown would surely 

 have spoiled the variety if each modified in the least the characteris- 

 tics of the cion grafted upon it. 



Having thus discussed the matter from the theoretical side, let 

 us examine for a moment the supposed proofs of the influence of the 

 stock and cion upon each other. I have searched with some care the 

 literature upon the subject, and find abundant examples cited as 

 demonstrations in favor of the phenomenon. But after carefully 

 weighing the evidence produced, there seems to laae but two cases in 

 which the observed change may not be due to simple nutrition on 

 the one hand, or uncongeniality of the union on the other. In all 

 these cases a cion taken from the supposedly modified tree would 

 produce the normal fruit. The two exceptional illustrations are, 

 first, the uniformity of roots of grafted apples, etc., in nursery rows, 

 and, second, the fact that cions taken from plants with variegated 

 foliage and grafted upon green-leaved stocks of same species, so mod- 

 ify the stock as to cause it to put forth leaves showing the charac- 

 teristic variation. 



In regard to the first, may not the rooting of the cion itself 

 perfectly account for the peculiarities of the roots as found in the 

 rows? Surely we need not go further for an explanation, if the 

 roots of nursery trees do mainly come from the cion. The first roots 

 are not to be accounted for in this way, but it certainly is true in 

 many cases, the cion's own roots ultimately equal or surpass those 

 of the stock. 



The second case is one of frequent occurrence, and upon nu- 

 merous kinds of plants. At first sight one would say this is an 

 excellent proof of the direct modification of the stock by the cion, 

 for the variegated twig from the plain-leaved stock may be used for 

 propagation with continued perpetuation of the peculiarity. But 

 such variegation is doubtless disease, and, unfortunately disease is 

 catching. We, therefore, simply prove that a disease is transmissible 

 by inoculation, instead of proving that the cion affects the stock. 



It therefore seems that we may at least render a Scotch verdict 

 upon the question, and say "not proved." At the same time, we 

 cannot deny the possibility of the occurrence, at least in some ex- 

 ceptional instances, of a radical constitutional change in either stock 

 or cion from an influence exerted by the one upon the other. If 

 such does ever occur in one direction as from the cion to the stock, 

 we should look for an equal influence the other way. 



