831 



The phenomena of union possible in grafting may be traced to the 

 heaUng processes of three classes of wounds which I have called bark 

 wounds, surface wounds and cleft wounds. 



The injuries termed bark wounds (as evident from the earlier chapters) 

 are those produced by a complete removal of the bark, so that the wood is 

 exposed without, however, losing any of its parts. The form of grafting 

 in which this peeling process forms the main part of the injury belongs to 

 the type of budding. Here, at the time of the greatest cambial activity, the 

 bark is raised for a certain distance from the wood of the stock and the 

 scion (bud) is inserted into the exposed place. This scion consists of a 

 single eye with a small bark shield {budding with bark), or of an eye which 

 has been cut out with some wood from the parent branch {budding with 

 ivood) or of a piece of an entire twig which can be inserted in different 

 ways and is shoved under the bark of the stock with its cut surface against 

 the wood cylinder {bark grafting). 



Under the term "surface wound" are included all the injuries in which 

 a piece of the wood is taken away together with a complete removal of a 

 part of the bark. The surface wound looks and behaves differently, accord- 

 ing to whether this wound surface is produced by a longitudinal or a cross- 

 cut. If the piece is cut from the axis longitudinally, the elements of the 

 bark and wood are exposed lengthwise. The rain water runs off easily 

 from this surface wound, while in a cut across the trunk it collects in little 

 troughs and can much more easily cause the decay of the wood. A hori- 

 zontal surface wound is always much more dangerous for the axis than one 

 running vertically. On this account in general practice diagonal cuts are 

 usually made, instead of horizontal ones. 



The kinds of grafting, in which surface wounds come into play chiefly, 

 or exclusively, belong to the type of "Copulation." The simplest form of 

 this consists in the setting of a scion in a diagonally cut surface, produced 

 by the cutting off of the tip from the stock where it is of the same thickness 

 as the scion. Most nearly related to this is the single and double saddle 

 graft. The scion and stock can be united also by actual longitudinal surface 

 wounds, if the stock is cut at the side in only one place without loosening its 

 tip. The scion either remains attached to the parent plant and, likewise, is 

 cut only at the side (ablactation), or cut off from the branch, as in other 

 forms of grafting, it is fitted to the stock by lateral paring. In order that 

 the scion may fit more closely in a lateral position, its lower end is cut to a 

 wedge and this end is forced into a cleft at the base of the surface wound 

 of the stock. In many plants (Camelias) the scion is not infrequently cut 

 to a short wedge and this wedge is forced into a lateral cleft in the stock, 

 produced by a short diagonal downward cut into the wood (insertion). 

 When the grafting fails, stock thus cut suffers least of all and after a short 

 time can be used again. 



The injury from which the trunk suffers most is the cleft wound. The 

 form of grafting with such wounds is cleft grafting. This was at first used 



