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. 
