TREES AS GOOD CITIZENS 
146 
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 
