elm. Trees like the sugar maple will not stand this treatment at
all. The willow is a tree that will stand the process very readily
and the Carolina poplar must be cut back every few years, in order
to keep its crown from becoming too tall, scraggy and unsafe.

[Illustration: FIG. 114.--A Limb Improperly Cut. Note how the stub is
decaying and the resulting cavity is becoming diseased.]

Covering wounds: The importance of immediately covering all wounds with
coal tar cannot be overstated. If the wound is not tarred, the
exposed wood cracks, as in Fig. 115, providing suitable quarters for
disease germs that will eventually destroy the body of the tree.
Coal tar is by far preferable to paint and other substances for
covering the wound. The tar penetrates the exposed wood, producing
an antiseptic as well as a protective effect. Paint only forms a
covering, which may peel off in course of time and which will later
protrude from the cut, thus forming, between the paint and the wood,
a suitable breeding place for the development of destructive fungi
or disease. The application of tin covers, burlap, or other bandages
to the wound is equally futile and in most cases even injurious.

[Illustration: FIG. 115.--Result of a Wound not Covered with Coal Tar.
The exposed wood cracked and decay set in.]


SPECIAL CONSIDERATIONS

Pruning shade trees: Here, the object is to produce a symmetrical crown
and to have the lowest branches raised from the ground sufficiently
high to enable pedestrians to pass under with raised umbrellas. Such