oads of fruit and burdens of ice crush
the tree; wind storms play mischief; bad pruning leaves long stubs,
and rot develops; cankers produce dead ragged wounds; fire-blight
destroys the tissue; a poorly formed tree with bad crotches splits
easily; grafts fail to take, and long dead ends are left; the tree is
injured by pickers; vandals wreak their havoc. All these accidents
must be met and the damages repaired. The surgeon must be summoned.

We must first understand how a wound heals on a tree. Note any
wound,--knot-hole on the trunk, place where wood has been removed. The
exposed wound itself does not heal; it is covered and inclosed by
tissue built out from the edges or periphery of the wound. This tissue
is like a roll. It is the callus. Eventually the tissue meets in the
center, and the lid is thereby put on the place, and it is sealed. The
exposed wood has died, if it is the cross-section of a branch or a
deep wound, and it remains under the callus a dead body. If the wood
has not started to decay in the meantime, the place is safe, but too
often invasion has begun before the process is complete, the rot
disease finally extends to the heart of the tree, causing it to become
hollow. If the center of the wound falls in, the callus cannot cover
it, and an open sore remains. In these cavities birds may sometimes
build.

Therefore there are two points for the surgeon to consider in respect
to the wound itself--whether it is so placed on the tree that the
callus forms readily; whether the wound is kept healthy during
exposure.

All ragged tissue being removed, deep-wound surfaces should be kept
aseptic. For ordinary cases, white-lead paint with plenty of linseed
oil is a good protective from the germs of decay. On old wood, no
longer active, creosote is good, perhaps followed by coal-tar.
Usually, however, paint is quite sufficient. Small exposures usually
receive no dressing. When the fresh surface wood is exposed by removal
of bark, it is necessary to keep the tissue from drying out, and
antiseptics are usually not applied. Bandaging with cloth is the usual
practice, after the wound is cleaned and trimmed.

The repairs fall into two classes,--those that require merely removal
of injured parts and treatment of the wounds, and those that demand
the ingrafting of new wood.

We have learned, in the discussion of pruning, that long projecting
ends of severed branches do not heal. The branches to be removed
should be