The Garden. 87 



part of the blood, consisting chiefly of matter, the same or similar 

 to the white of an egg, which, being thus separated from the rest 

 of the blood, thickens by the heat of the body, as the white of 

 the egg does by boiling. If the lips of the finger cut according- 

 ly be kept close together by sticking plaster, they will become 

 united by means of this natural glue or serum in little more than 

 a day. Upon the same principle I once succeeded, as others 

 have done, in managing to unite the whole upper joint of a finger 

 which a boy had chopped oil' by machinery; and experiments 

 have been successful in causing the spur of a cock to unite and 

 grow upon his comb. 



" It is upon similar principles that the science of grafting is 

 founded; for if a young branch, like the boy's finger, be taken off 

 by a clean cut, and the cut extremities immediately joined, the 

 descending pulp will thicken like the watery part of blood, and 

 while it remains soft the sap from the cut end of the sap-vessels 

 will force its way through to their continuation above in the cut 

 slit, which, if the process be successfully managed, will grow as 

 well, or nearly, as if it never had been cut. 



" If, again, instead of applying the same cut scion to the part 

 it was cut from, a scion from another tree be applied, as if I had 

 applied to the boy's finger the tip of another boy's finger, chop- 

 ped off by the same accident, there seems no good reason to 

 doubt that a similar healthy joining might, by care, be effected. 

 In the case ^f animals, indeed, such joinings are rare, because 

 rarely tried, but in garden plants they are exceedingly common, 

 for the purpose of continuing esteemed varieties of valuable fruits 

 and flowers, accidentally produced by cultivation, as well as for 

 forwarding the fruiting of young trees, since seedlings require 

 years to arrive at a bearing state. 



" On examining the joining of a graft about a fortnight after it 

 has been made, I have found, as in a healing finger-cut, a number 

 of small roundish grains, in the form of a thin layer, produced 

 from the thickening of the pulp, and destined to form the hard 

 substance terrr^cl the callus, which in general projects a little 

 externally, and the scar differs in appearance from the other parts 

 of the bark. It is, however, only in the space between the pulp- 

 wood and the bark that the uniting substance is formed, and 

 therefore it is evident that the slip to be grafted must have this 

 part applied to the same part of the stock, and, if these difier in 

 thickness, at least to one side. 



" One of the most obvious principles of this process is, that 

 the sorts to be grafted should be alike, or nearly alike, because, 

 in that case, the arrangement of the sap and pulp-vessels being 

 similar, dieir cut ends will more readily apply mouth to mouth, 

 and less obstruction or interruption of the circulating juices will 

 take place. 



