14 



PRACTICAL TREE REPAIR 



who is doing tree repairing. If an accident occurs, 

 his first thought is of the cambium. If he is mak- 

 ing an incision or filling a cavity, one eye must be 

 constantly on the cambium. He must learn all its 

 wills and won'ts, what it does and how it does it, 

 what can be done to it and what can not. 



Cam- 

 bium 



Sap 

 >A/ood 



Heart- 

 Wood 



Cross section of the trunk of a tree 



For the cambium is the only growing part of the 

 tree (besides the young leaves and the tips of twigs 

 and roots) and if growth is to be made the cam- 

 bium must make it. It is the vital, growing cam- 

 bium which each year lays on a thin, strong layer 

 of new wood over the whole surface of the frame 

 of the tree, which builds out a tough shield of bark 

 to protect itself and the wood beneath it. It is the 



