Feb. i9, i9i7 Arsenical Injury through the Bark of Fruit Trees 
303 
The results show that the washing may have slightly decreased the 
injury in some cases. This was not uniformly true, for with arsenic 
trioxid and ortho zinc arsenite the washed chemical caused fully as much 
injury as the unwashed, and with copper aceto arsenite and triplumbic 
lead arsenate the results were nearly alike. In fact diplumbic lead 
arsenate was the only chemical that showed a striking improvement as 
a result of washing. This is probably due, as suggested by Dr. Headden, * 1 
to a change in the composition of the lead arsenate from the diplumbic 
to the triplumbic as a result of washing. A close comparison of the 
results is fruitless, owing in part to the rather large experimental error 
of the methods here used. The essential fact is that both washed and 
unwashed chemicals of the purest brands obtainable do cause severe 
injury. 
EFFECTS OF ADDING DIME TO THE ARSENICALS 
It has frequently been recommended that lime be added to arsenical 
insecticides, especially copper acete arsenite, to lessen the possibility of 
injury when sprayed on foliage. To determine whether this would 
materially lessen the injury under the conditions of these experiments— 
namely, when the arsenicals are applied to the wounded bark—1 gm. of 
partly air-slaked lime 2 was mixed with the arsenical contained within 
each bandage. The following arsenicals, 10 gm. each, were used, two with 
lime and two without: 
Calcium arsenite, Baker. 
Copper aceto arsenite, Baker. 
Lead arsenate, diplumbic, Baker. 
Lead arsenate, diplumbic, Grasselli. 
Lead arsenate, triplumbic, Baker. 
Lead arsenate, triplumbic, Grasselli. 
Zinc arsenite, ortho, Baker. 
Zinc arsenite, “Ortho 40,” California 
Spray Co. 
Lime only. 
A comparison of the injury with and without lime shows little evidence 
that lime lessens the injury from any of the chemicals tested. It appeared 
at first glance to lessen the injury from Grasselli’s triplumbic lead arsenate 
and Baker's ortho zinc arsenite, but as it failed to do so with Baker's 
triplumbic lead arsenate and “ Ortho 40” zinc arsenite, we are led to 
believe that this apparently beneficial effect is largely a matter of coinci¬ 
dence. We are strengthened in this belief by the fact that several 
duplicate tests in this series differ‘so much from each other. The lime 
alone caused no injury. 
differences in varieties of apple, pear, and plum 
Field observations have led to the belief among horticulturists that 
there is a difference in varieties of apple with reference to the resistance 
of their foliage to injury by arsenical spray mixtures. The Ben Davis 
1 This suggestion was offered verbally by Dr. Headden in 1910. 
1 Quicklime was allowed to air-slake until it had taken a powdered form, but was still strongly alkaline to 
litmus paper. 
