PRUNING SHADE TREES 145 



surface with a coat of shellac. This should be applied 

 with a brush to the edges of the wound, covering the bark 

 and at least half an inch of the wood. This should be done 

 as soon as the cut is dry enough to hold the shellac, and 

 within three or four minutes at the most after the 

 cutting. The shellac serves to prevent loss of moisture, 

 and since the cambium, or inner bark, will die if it is 

 allowed to dry out, the coating is an essential step. 

 Wounds more than half an inch in diameter require 

 artificial protection during the process of healing. This 

 protection is given by painting with shellac and following 

 this by coating the center of the wound with coal tar, 

 creosote or lead paint. The shellac forms one of the best 

 protecting covers for the sensitive tissue between the 

 bark and the wood where growth takes place, and which 

 is called cambium layer or cambium. It is the least 

 injurious to this vital but sensitive part of the tree of all 

 of the substances now known. As it is not permanent 

 when exposed to weather, especially moisture, it needs 

 to be coated with one of the other substances mentioned. 

 The shellac need not be applied to the whole wound if the 

 cambium is thoroughly covered, including an inch of the 

 adjacent wood. 



If the wound is large, it 'should be sterilized by applying 

 antiseptic after the application of the shellac. There are 

 several preparations of this nature, and among these one 

 of the best is creosote, which has a particular value in 

 destroying the germs of decay and preventing destruction. 

 The creosote is applied with a brush and should cover all 

 of the exposed wood not covered by the shellac. On top 

 of the shellac and creosote the surface should then be 

 covered with a thick coating of coal tar to keep out 

 water. This waterproof coating should be renewed from 

 year to year, whenever there is a tendency to crack or 



10 



