160 PRACTICAL TREE REPAIR 



is often necessary that the treatment given them 

 be rapid and economical. If such a cavity is 

 shallow the best way to handle it is to employ the 

 open system, to be described in the next chapter, 

 in which no filling is used. 



Deeper holes, in which the open treatment 

 would involve too large an incision and the cutting 

 away of too much bark, must be filled. Although 

 in some cases complete removal of the decayed 

 wood is neither possible nor desirable (and of 

 those cases we shall have more to say in a later 

 chapter) , for the most part the general principles 

 of cavity work apply as well to small holes as to 

 large ones. 



The first step, then, is the removal of the de- 

 cayed wood. To do this thoroughly often in- 

 volves considerable difficulty. The mouth of the 

 hole must usually be enlarged, especially down- 

 ward, and it may be necessary, if the decay runs 

 far down the trunk, to cut in from below to get 

 at it. More than one such opening may be re- 

 quired. In that case, a considerable distance 

 should be left between the openings, for other- 

 wise the intervening patch of bark will die. 

 These holes must be cut only when it is absolutely 

 necessary, for every such opening increases the 

 risk of the entrance of water and of other troubles 

 with the filling. The excavation finished, the 



