Feb. 19,1917 Arsenical Injury through the Bark of Fruit Trees 287 
required more frequent watering, and were applicable only to branches 
having the right kind of sag, which in time became difficult to find. 
In those bandages that were not covered with rubber the conditions of 
moisture and aeration were closely similar to those often found about the 
crowns a few inches beneath the surface of the ground. They were wet 
with distilled water every day, but owing to our atmospheric conditions, 
that favor rapid evaporation, they were, as a rule, nearly or quite dry 
an hour or more before the daily watering. Those that were wrapped 
in rubber were wet continuously and the aeration was not so good, but 
many comparative tests gave results almost identical by the two methods, 
or as nearly identical as the duplicates were by either method alone. We 
were, therefore, led to believe that excessive moisture and imperfect aera¬ 
tion did not materially influence the injury, which had usually begun in a 
few days and was complete within two or three weeks from the time of 
treatment and probably before the bark would make any abnormal growth 
due to lack of air or excessive moisture. 
In the few cases where roots a little distance from the crown were 
treated it was by the same methods as described for the branches. Root 
treatments required so much labor, however, that only enough were made 
to assure us that the susceptibility of roots is not greatly different from 
that of branches. This work was further complicated by the difficulty 
of finding roots of suitable size that did not bear rootlets which, when 
broken off by digging, presented unnatural openings for the entrance of 
arsenical solutions. 
This work, was all carried on in the college Orchard at Bozeman, where 
some branches could be injured and removed without serious damage to 
the remainder and where, by good fortune for this work, a few rows of 
trees were to be removed entirely and were available for the most severe 
treatment of crowns, trunks, and large branches. 
The tests were made almost entirely upon apple trees, though pear and 
plum were tried in a few cases. Where the latter were used, they are 
specifically mentioned; otherwise, the results described in the following 
pages apply entirely to the apple. 
ARSENICAL COMPOUNDS USED 
In carrying on work of this kind much difficulty is encountered in 
determining the exact composition of arsenical compounds regularly 
put upon the market or even in getting made to order all the different 
compounds wanted, free from mixture with other arsenicals. There is a 
great tendency on the part of insecticide companies to prepare mix¬ 
tures, especially of the diplumbic and triplumbic lead arsenates. We 
were fortunate, however, in securing, on special order from the J. T. 
Baker Chemical Co., of Phillipsburg, N. J., most of the more important 
arsenicals apparently quite pure. 
