TREES AS GOOD CITIZENS 
162 
removed. To leave decayed or diseased tissue will spoil 
the whole job. 
Repair begins by digging out the diseased or decayed 
wood. For this purpose the operator should be equipped 
with a knife, gouge, chisels and mallet. He should not be 
alarmed at the growth of the cavity brought about by his 
abode f 
How a cavity is caused and how to treat it. 
a. —Stub left after pruning. 
b. —Decay starting in stub. 
c. —Decay well advanced. 
d. —Cavity formed in trunk. 
e. —Section of trunk showing cavity. 
f. —Cavity cleaned out and ready for closing. 
digging, for it is necessary to remove the affected tissue, 
no matter how large the resulting hole may become. To 
make sure that the last trace of decay or disease is taken 
out, the digging should extend into healthy wood. On 
the outside, the rolls of bark which have grown up at the 
edges of the cavity should be pared off to a point even with 
the natural shape of the trunk. 
When the cavity has been cleaned, exposing a smooth 
surface of sound wood at all points, the cambium and 
adjacent parts should be painted with shellac; then the 
walls should be sterilized with copper sulphate or creosote 
applied with a brush. This should be followed by at least 
