DISEASES OF PLANTS 
or no difference whether the center is 
wood or stone. 
The bark is a protection for the tree. 
Where the bark remains intact, the woody 
fibers of the inside are preserved for 
generations and for centuries, unless some 
outside agency kills the tree. Destroy any 
part of the bark by any means whatso- 
ever, and when the protection is gone the 
wood decays. Once decay secures a start, 
its progress is rapid. It continues until 
checked by artificial measures or until the 
tree becomes so weak that it is blown 
over in a windstorm. The tree may ap- 
pear to be in a perfectly healthy con- 
dition even with the entire inside rotted 
away, simply because the vital parts 
(three or four inches on the outside) are 
the last to be destroyed. Decay attacks 
and disintegrates the dormant tissues 
first, and gradually works outward. Ce- 
ment in trees fulfills the three-fold pur- 
pose of stopping decay, serving as a struc- 
tural support, and providing a surface 
over which the bark may heal. 
Is cement work in trees a success? In 
other words, is tree surgery a real or fan- 
cied good? Does it save the trees? That 
depends on the vitality of the tree, and 
the ability of the man who undertakes 
the work. A man may be so nearly ex- 
hausted and so low in vitality that all the 
doctors in the land could not save him. 
A tree may be the same. If it is weak 
and far spent the chances are against it. 
If it is vigorous and healthy, the chances 
are all in its favor if the man who oper- 
ates knows how. The only real test of a 
tree’s vitality is the appearance and dens- 
ity of the foliage. A rich-green abundant 
foliage indicates health, and vice versa. 
And still almost the entire inside may 
have rotted away! 
Tree surgery, or that part of it pertain- 
ing to the filling of cavities, is aptly com- 
parable with dentistry. The three funda- 
mental principles of each are the same. 
The dentist must remove all decay and 
prevent more, prepare the cavity so that 
the filling will stay permanently in place, 
and exclude all foreign substances. The 
tree surgeon must do the same things, al- 
though the means to that end may differ 
somewhat. To remove the decay from a 
893 
cavity requires chisels and gouges of va- 
rious lengths and sizes. The smaller 
cavities are not exceedingly difficult, al- 
though they require the same exacting 
care. The larger a cavity becomes the 
harder the task of removing the decay. 
It must be followed in the cracks and 
crevices and away up and down through 
limbs and trunk as far as it goes. It is 
sometimes burned out, although this 
measure is very dangerous unless applied 
by a man who thoroughly understands its 
use. When the decay is removed, it is 
wise to apply corrosive sublimate or a 
similar solution to destroy any remaining 
fungi. The walls of the cavity must then 
be thoroughly waterproofed to protect the 
wood. The waterproofing material must 
be durable, penetrating and adhesive. 
This is the first step and is very similar 
to the first principle applied by the den- 
tist. 
Perhaps the most difficult and trying 
part is in preparing the cavity so that the 
filling will stay permanently in place. 
This requires more than a knowledge of 
cement and its use. It requires more 
than a scientific knowledge of trees. 
It requires both these and more. 
The operator absolutely must know the 
practical methods of tree surgery, and 
have acquired almost instinctive skill 
with his hands by long practice. Cement 
improperly put into a tree is far worse 
than none. The law does not permit un- 
trained men to practice upon the human 
body or even that small part of it called 
the teeth. Why should untrained men 
operate on trees which are just as much 
alive as human beings? 
The cavity must be thoroughly braced if 
it has any size. No man can set down in 
words the manner in which this should 
be done, because it depends absolutely 
upon the size, shape and general condi- 
tion of the cavity and the strength of the 
woody shell. The operator must deter- 
mine the weakest side or point and brace 
it with great care. He must know what 
stress must be borne by the tree and in- 
sert steel ribs or truss rods to reinforce 
the trunk. All this must be done with a 
full appreciation of the fact that there 
will be some sway to the tree. Often- 
