Feb. i9,1917 Arsenical Injury through the Bark of Fruit Trees 
317 
have been made elsewhere, with varying results. The latter possibility 
has received some consideration from Grossenbacher (3, 4) especially, 
but we are still left in doubt as to the application of his work to condi¬ 
tions in the Rocky Mountain region. 
On the part of some investigators of crown injuries of fruit trees, there 
seems to be a tendency to take a very narrow view of the field and to 
ascribe to some one cause a number of troubles characterized by injury 
to the bark on or near the crown. That such conditions are caused by 
different agencies is well established, and it seems- highly improbable 
that we will make much headway by trying to discredit the work of 
others in support of a narrow hobby. 
CONCLUSIONS 
(1) The periderm on the smooth bark of apple trees is practically 
impervious to arsenical solutions. 
(2) If such solutions are admitted during the growing season, more or 
less injury will follow. 
(3) The solutions may be admitted through wounds, lenticels, or 
latent buds. 
(4) As the trees become older and rough bark is produced, the cracks 
made in its production will admit arsenical solutions to the inner tissues, 
which will be injured. 
(5) Roots and branches of equal size and with similar bark are about 
equally susceptible to arsenical injury. 
(6) If the injury is rapid, for example, the arsenic gaining entrance 
through a wound in the smooth bark, very definite longitudinal streaks 
will be produced in the bark and sapwood. 
(7) If the injury is slow, the arsenic gradually entering through 
cracks of the normal rough bark, such streaks are very little in evidence. 
(8) Paint applied to fresh wounds offers a partial, but not complete 
protection. 
(9) Of the arsenical compounds used as insecticides, calcium arsenite 
is the most injurious when admitted to the inner bark. 
(10) The injury is not necessarily due to impurities in the arsenical 
compounds. 
LITERATURE CITED 
(1) Baix, E. D. 
1909. Is arsenical spraying killing our fruit trees? In Jour. Econ. Ent., v. 2, 
no. 2, p. 142-148. 
(2) -Titus, E. G., and Greaves, J. E. 
1910. The season’s work on arsenical poisoning of fruit trees. In Jour. Econ. 
Ent., v. 3, no. 2, p. 187-197, pi. 12-16. 
(3) Grossenbacher, J. G. 
1909. Crown rot, arsenical poisoning and winter injury. New York State Agr. 
Exp, Sta. Tech. Bui. 12, p. 370-411, 8 pi. Bibliography, p. 409-411. 
( 4 ) — 
1912. Crown rot of fruit trees: Field studies. New York State Agr. Exp. Sta. 
Tech. Bui. 23, 59 p., 23 pi. 
