FLOWER-GARDENING. 159 



place by the cellular substance only, and the union is so im- 

 perfect that a slight degree of violence suffices to dissever 

 them. 



346. 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. 



347. When, in such instances, the communication between 

 the stock and the scion is so much interrupted that the sap 

 can no longer ascend with sufficient rapidity into the branches, 

 the latter die ; as in many Peaches. 



348. This incomplete union between the scion and its stock 

 is owing to some constitutional or organic difference in the 

 two. 



349. Therefore, care should be taken that, when plants are 

 grafted on one another, their constitution should be as nearly 

 as possible identical. 



350. 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 

 constitutional difference is very decided. 



351. Hence it is only species very nearly allied in nature 

 that can be grafted on each other. 



352. As only similar tissues will unite (19), it is necessary, 

 in applying a scion to the stock, that similar parts should be 

 carefully adapted to each other ; as bark to bark, cambium to 

 cambium, alburnum to alburnum. 



353. The second is more especially requisite, because it is 

 through the cambium that the woody matter sent downwards 

 by the buds must pass ; and also because cambium itself, being 

 organizing matter in an incipient state, will more readily form 

 an adhesion than any other part. 



354. The same principles apply to buds, which are to scions 

 precisely what eyes (319) are to cuttings. 



355. Inarching is the same with reference to grafting, that 

 layering (324) is with reference to striking by cuttings. 



