CHAPTER VII 



THE FILLING OF CAVITIES 

 MATERIALS AND TOOLS 



THE treatment of cavities is the part of tree 

 repair which presents the greatest technical 

 difficulties, as well as the largest opportunities for 

 the application of the principles of the nature and 

 growth of trees and of the spread of decay. The 

 causes of cavities in trees have already been 

 stated. The many ways in which they are dan- 

 gerous have also been touched on in several con- 

 nections. Perhaps the clearest way to state the 

 potential peril which lies in every cavity is to say 

 that all cavities grow. Slowly, but steadily, every 

 cavity grows larger and larger, until the exchange 

 of sap between roots and leaves is so far cut off 

 that the tree dies, or until the supporting frame- 

 work of the tree is so far eaten away that the tree 

 is broken down by the wind. Every cavity is 

 therefore a stage in the steady course from the 

 bark wound to the hollow, shattered tree. Other 

 factors may bring about the death of the tree be- 

 fore the cavity gets in its work, but the cavity is 



102 



