1 84 PRACTICAL TREE REPAIR 



that not a speck of the wood is left exposed. In- 

 spect the dressing yearly. 



The open system is especially suited to the 

 treatment of small cavities in healthy trees. Such 

 a one is illustrated in the accompanying drawings. 



One of the first methods of dealing with wounds 

 and cavities was to cover them with sheet metal. 



Shallow decayed spot gouged out 

 and tarred, without filling 



The idea was not only to keep out the elements 

 and insects and fungi, but also to provide a sup- 

 port for the calluses growing from the sides of 

 the mouth of the cavity. It was at one time gen- 

 erally thought that tinning would prove the best 

 treatment for almost every type of cavity, but it 

 is now realized that its value is rather strictly 

 limited. These limitations follow directly from 

 the nature of the material and the way in which 

 it is applied, and a discussion of them will be de- 

 ferred until those points have been taken up. 



