74 SCIONS. 



takes place by the cellular substance only, and 

 the union is so imperfect that a slight degree of 

 violence suffices to dissever them. 



And in such cases the buds are fed by their 

 woody matter, which absorbs the ascending sap 

 from the stock at the point where the adhesion 

 has occurred ; and the latter, never augmenting 

 in diameter, is finally overgrown by the scion. 

 When, in such instances, the communication 

 between the stock and the scion is so much in- 

 terrupted that the sap can no longer ascend with 

 sufficient rapidity into the branches, the latter 

 die ; as in many Peaches. 



This incomplete union between the scion and 

 its stock is owing to some constitutional or or- 

 ganic difference in the two. 



Therefore care should be taken that when 

 plants are grafted on one another their constitu- 

 tion should be as nearly as possible identical. 



As adhesion of only an imperfect nature 

 takes place when the scion and stock are, to a 

 certain degree, dissimilar in constitution, so will 

 no adhesion whatever occur when their consti- 

 tutional differences are very decided. 



Hence it is only species very nearly allied in 

 nature that can be grafted on each other. 



As only similar tissues will unite, it is neces- 

 sary in applying a scion to the stock that similar 



