146 TREES AS GOOD CITIZENS 



peel. Even when no crack is apparent, recoating will do 

 no harm, and it may prevent trouble from causes not 

 visible. If shellac is not used the protective coatings 

 must not reach the outer edges of the wound, where they 

 will come into contact with the cambium as the latter is 

 so sensitive to the chemical action of the material used 

 for protection it may be killed by contact with it. It is 

 a good rule not to allow the weatherproof applications to 

 come within half an inch of the outer edges of the wound, 

 except to cover shellac. The protective coating is applied 

 with a brush, and if coal tar is used it is usually necessary 

 to thin it by heating. Two coats should be applied, and 

 these should be repeated from year to year until the 

 wound is healed. 



In pruning it is well to start at the top of the tree and 

 work downward, as this not only simplifies the shaping of 

 the crown but also makes it easy to remove any limbs 

 or branches that may lodge in falling. In addition to 

 cutting close to the trunk or remaining limb, it is impor- 

 tant to make a clean wound, free from projections or 

 raggedness, as a rough surface will impede healing. Care 

 must be taken also to prevent injury to the surrounding 

 bark. Pruning saws are made especially for this work, 

 but a rather fine-toothed handsaw may be used. One 

 with seven teeth to the inch is good for most purposes. 

 Pruning saws come with teeth on one or both edges. 

 The two-edged ones should be avoided, as the back is 

 liable to do damage in close work. Pruning saws sup- 

 ported on a frame like a meat saw but with the blade on a 

 swivel are especially desirable. 



Great care must be exercised to keep a limb or branch 

 from splitting and breaking the surrounding bark. In 

 removing limbs of moderate size this is best accomplished 

 by sawing underneath first and finishing from above. In 



