REPAIR OF SHADE TREES 165 



cates the greatest need. The bolting should be done, of 

 course, before the cavity is filled. 



In considering cavities and their treatment, it is impor- 

 tant to remember that large cavities offer serious problems 

 and give chances for complications, and that for this 

 reason it is generally best to leave them unfilled or open 

 but if it seems best to have them filled, it will be wise to 

 place the work in the hands of an expert rather than to try 

 to repair them without the special knowledge and experi- 

 ence which are so essential. 



