THE EDITOR'S ALPHABET OF GARDENING. 



141 



" The principle upon which this is done, is to prevent the oxygen of the at- 

 mosphere from getting to the fluid pulp at the joining, where it would unite 

 with the carbon and form carbonic acid gas, and thereby rob the pulp of its 

 solidity.* The exclusion of light is necessary on the same account, for a similar 

 reason, as in the case of a finger-cut, the oxygen would unite with the carbon 

 and prevent the thickening of the matter from the blood. On the same account, 

 moisture, by supplying oxygen, would be injurious; and dryness might act 

 both by exhausting the pulp and by causing the edges of the bark to shrivel 

 and gape, which would facilitate the entrance of the air with its oxygen. 



" It must be obvious from this simple principle, (not that I am aware of ever 

 before stated it with reference to grafting), that no composition, whatever 

 may be said of its peculiar power of healing, can act in any other way than 

 this ; no more than the farrago of plasters and salves for healing flesh-wounds 

 and cuts, which are only good in so far as they keep the lips of the wound 

 together, and exclude oxygen and light. 



" Grafting by Approach, or In-arching. 



tf This is to grafting what layers are to striking, the graft-slip not being cut off, 

 but taken from a plant growing near the stock upon which it is suffered to 

 remain till the joining is completed. Mr. T. A. Knight employed this mode 

 not only for the purpose of filling up from itself the parts of a wall-tree defi- 

 cient in bearing wood (a), but also of improving the quality of fruits. It might 

 be advantageously used in a similar way to fill up the gaps in quick-set and 

 other hedges, where beauty of appearance is considered of consequence. 



" Slip, or Scion Grafting. 



" The slips taken off from one plant and joined to another, have the parts to 

 be joined cut in various manners, according to the sort of plant, the size of the 

 parts, and other circumstances. These will be better understood from the 

 figures below than from mere verbal description. 



* This is explained in the first part of the work under " GARDEN CHEMISTRY." 



