44 PRACTICAL TREE REPAIR 



sound callus at any point, the callus must be cut 

 back correspondingly or the hole must be filled. 

 However, a healthy callus will bridge or fill up 

 quite a deep wound, provided it be so thoroughly 

 painted or tarred that no decay or boring insects 

 can get at the wood. 



In the case of very large bark wounds, where, 

 perhaps, the wood is checked and here and there 

 invaded by borers, and it is evident that the tree 

 cannot heal over the wound in many years, it 

 should either receive repeated coats of a very 

 heavy dressing, reinforced, perhaps, with cotton 

 padding, or it should be covered with zinc. If 

 the last course is decided on, after the wound is 

 cleaned and trimmed up the zinc is cut to fit it, a 

 paper pattern usually being made first. The zinc 

 should preferably come up rather close to the edge 

 of the wound, but should in no case overlap in the 

 least the cambium or the bark. Having the zinc 

 ready, paint the wound thoroughly, the back of 

 the zinc likewise, and nail the zinc in place with 

 shingle nails an inch or two apart. Its outer sur- 

 face must then be painted, an especially heavy 

 coat being flowed over the edges to make sure 

 that they are water-tight. Thin sheet copper 

 also does very well for this kind of work. The 

 use of sheet metal will be described more fully in 

 a later chapter. 



A slightly different class of wounds is caused 



