286 
Journal of Agricultural Research 
Vol. VIII, No. 8 
EXPERIMENTAL METHODS 
We have endeavored, among other things, to reproduce as nearly as 
possible the conditions obtaining about the crowns of the trees as a 
result of spraying, especially with reference to the presence of the arseni- 
cals in immediate contact with the bark, and the moisture necessary for 
bringing them into solution. When crowns were to be treated, this was 
accomplished by carefully removing the earth without injuring the bark, 
applying the arsenical, and replacing the earth. The natural precipitation 
and the regular orchard irrigation were depended upon to furnish the 
necessary moisture. This method, while simulating closely the conditions 
brought about by orchard spraying, is obviously cumbersome. It is slow 
of application, frequent examination to note the course of the injury is 
difficult, and as each tree could be used for only a single treatment a good- 
sized orchard would have been required to furnish trees for all the tests 
we have made, the cost of which would have been prohibitive. We there¬ 
fore made considerable use of trunks and branches. 
When the trunks were treated, this was done by a method shown us at 
the Utah Experiment Station by Dr. E. D. Ball, to whom we are indebted 
for the suggestion. A funnel of white rubber sheeting was constructed 
about the trunk and sealed to it with tree tanglefoot (PI. 79). Inside 
this, the arsenical was placed, distilled water was added, and the whole 
covered with a hood of rubber sheeting sealed to the trunk above and 
loosely overhanging the funnel. This served to keep out rain water and 
permitted free access of air. This method is open to most of the objec¬ 
tions mentioned above and, furthermore, the rough, shaggy bark of the 
trunk makes it very difficult to keep the funnels from leaking. If one 
attempts to smooth this up by scraping there is considerable danger of 
making unnatural breaks in the corky bark. It is not unlikely that Dr. 
Ball used a more satisfactory wax than tree tanglefoot. As a matter of 
fact we used this method in only nine cases—those reported in Table VIII. 
The great majority of the tests recorded in this paper were made on 
branches of various sizes, and the chemical was held in contact with them 
by means of a bandage of absorbent cotton protected by a wrapping of 
surgeon's gauze, the whole being wet with distilled water. As the orchard 
had never been sprayed, it seemed desirable at the outset to prevent the es¬ 
cape of any of the arsenic from the bandage to the soil so that any injury 
that might occur could not possibly be attributed to absorption through the 
feeding roots. This end was attained in the early experiments by select¬ 
ing branches that showed a decided sag at some point and placing 
the bandage at the lowest part. A metal box was hung close under the 
bandage to catch any drip produced by rains. Later we tried wrapping 
the bandages in a dental rubber dam to prevent the drip, and omitting the 
boxes (PI. 80). In repeated tests the two methods gave results almost 
identical, so the boxes were discarded as they were more cumbersome, 
