i8 



PRACTICAL TREE REPAIR 



region of the cut cambium layer all around the 

 wound. It will press firmly against the cut sur- 

 face, covering and protecting it. A cross-section 

 of this callus will show that it is structurally like 

 other parts of the trunk, a layer of bark enclosing 

 a thin layer of cambium, beneath which is the sap- 



Vertical section through a pruning wound and the first, fourth, 

 and seventh years subsequently, showing growth of callus 



wood, though the wood of a callus is harder and 

 more closely woven than ordinary wood. Every 

 year a new layer of wood will be deposited on the 

 callus by the callus cambium, and before many 

 years the wound will be completely covered. 



The callus does not, of course, actually coalesce 

 with the cut surface, but merely rolls over it. As 

 wood is added to the inner edge of the fold, the 

 bark which is under the lip, so to speak, is pressed 

 against the cut surface, and if the limb were sawed 



