892 
Spraying usually gives immediate 
but temporary relief. It is the meth- 
od, however, to which we must resort 
at present in order to control the 
large majority of plant diseases. 
The principle of spraying depends upon 
the fact that these fungi are more delicate 
and more easily killed by poisons than 
are the plants on which they grow. The 
object is to use some poisonous solution 
which will not injure the plant that you 
are “doctoring,” but will kill the fungus 
parasite, or if applied as a preventive, will 
prevent the fungus from entering the 
host plant. For instance, if a plant is 
covered with copper sulphate or some 
other poisonous solution the _ spores, 
which lodge on its leaves and stems, can- 
not grow and produce disease but will 
be killed by the poison. In this way 
plants are protected. In this connection, 
too, we can readily see the necessity for 
making the spraying thorough. Fungus 
spores lodging on exposed surfaces would 
germinate and grow directly into the leaf 
or stem, and actually undermine the 
neighboring surfaces, which might be 
thoroughly coated with the poison. So 
spraying in order to be effective must 
be done in such a way that every particle 
of surface of the susceptible part of the 
plant is covered. No possible exposed 
place should be left on the leaves or the 
fruit or the stems where the fungus could, 
perchance, enter. 
H. W. Barre, 
Botanist South Carolina Agricultural Experi- 
ment Station, Clemson College, S. C. 
Saving Trees by the Use of Cement 
How the Tree Surgeon Stays Decay with 
Cement Fillings 
In our minds disease and suffering are 
so closely associated that we ordinarily 
regard the allaying of pain as the funda- 
mental function of medicine and surgery. 
We are apt sometimes to overlook the 
economical gain to the community which 
the maintenance of health among its 
members implies. The economic factor is 
of course quite prominently displayed in 
veterinary practice, though here also 
there is pain to be alleviated. When we 
come to the vegetable kingdom the pure- 
ly “benevolent” motive for medication is 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
practically absent. This, perhaps, is the 
reason why we hardly class plant surgery 
in our minds in the same category as the 
treatment of human and animal ailments. 
But while there is thus a pronounced 
difference in the two fields, in most other 
respects they are very similar. 
The plant, like the animal, is a living 
thing, subject to the attacks of enemies 
in life and ultimately to death. Like the 
stricken animal, also, the diseased plant 
is ready to receive at the hands of man 
beneficent medical or surgical treatment. 
And in plant surgery, as in the practice 
of the art on the human being, a species 
of asepsis is essential for success. 
In the science of plant medication quite 
an important role is played by cement. 
This material has, in the practice of tree 
surgery, a definite, well defined purpose, 
and certain fixed methods of application. 
This does not mean that all trees should 
be treated alike. This is obviously im- 
possible. However, there are certain 
principles which must be incorporated 
into each cavity, and these principles are 
the same for each case. 
In order to understand the use of ce- 
ment in trees we must understand the 
purpose of the operation and something of 
the life’s processes of the tree. The in- 
side of a tree is practically dormant, ex- 
cept the few layers of woody fibers just 
under the bark. The sap ascends in these 
outer woody fibers, and enters the leaf, 
where it undergoes the chemical change 
which produces the “tree-food.” This 
tree-food descends just underneath the 
bark, building as it goes. It continues to 
descend and build until it reaches the 
tiniest roots. Thus we see a real circu- 
lation in the tree. The central tissues 
serve no purpose save that of physical 
support. If any other substance can take 
its place and accomplish the same result, 
the tree will continue to live and thrive 
indefinitely, provided the new center of 
the tree is sealed tight to the adjoining 
tissues and remains so. The real life ofa 
tree is represented by the bark, the cam- 
bium layer just behind it, two, three or 
four inches of sap-wood just behind the 
cambium, the leaves, and the roots. If 
these parts are vigorous, it makes little 
