PLANT AFFINITIES 



refuses also to accept its stem as a companion 

 organism when grafted or budded. 



However carefully the grafting experiment 

 may be performed in such a case, the uncon- 

 geniality between stock and cion is soon made 

 manifest. The surfaces do not unite; or if union 

 takes place there is but slight tendency to grow; 

 or the cion does not thrive, and is presently 

 blighted. 



There are all gradations — from actual poison- 

 ing in which there is no tendency whatever to 

 unite, to a partial or even temporarily complete 

 union, followed by separation even after years of 

 growth — according to the degree of antagonism. 



This chemical antagonism between the tissues 

 of the plants themselves affords the surest evi- 

 dence of the long periods of time during which 

 the two species have lived under more or less 

 divergent conditions, and have been occupied, 

 each in its own way, in the development of new 

 characteristics. Yet that such intimate differences 

 of constitution should obtain between species that 

 show many outward points of resemblance must 

 always be matter for surprise to the plant lover 

 whose attention is called to it for the first time. 



That this intimate record of grades of 

 cousinship should be permanently graven in the 

 protoplasm of the plant itself is one of the most 



[47] 



