PHYSIOLOGICAL EFFECTS ON PLANTS 15 
ments showed that gas was most injurious to foliage 
on sunshiny days late in the fall between 9 A.M. and 
4 P.M.; that the dormant leaf and fruit buds treated 
with 0.20 gramme cyanide per cubic foot were not in- 
jured ; that burned leaves, that is, those injured by 
the gas, fall readily; that trees treated in the morning 
before 9 o’clock and in the afternoon after 4 o’clock, 
even in sunshine, have the leaves little affected; that 
trees treated at night with normal doses do not have 
the foliage hurt at all. 
On March 18, 1898, experiments were begun upon 
plum trees, using the same standard dose, just as the 
buds were unfolding, and observed no injurious effects 
whatever. June 3, 1898, eight young plum trees, 
from 8 to 10 feet in hight, were fumigated with 0.16 
gramme cyanide. The exposure varied from 5 to 12% 
minutes, in the sun at 80° F.; in every instance all 
the lice were killed and the foliage not injured. July 
8, 1898, three cherry trees were fumigated with 0.16 
gramme cyanide from 5 to 10 minutes. The trees 
were infested with the cherry slug. A five-minute 
exposure did not injure the foliage at all, but did not 
destroy over 60 per cent. of the slugs; on the other 
hand, 7% to 10 minutes destroyed all the slugs, but 
severely hurt the leaves. June 13, 1898, two pear 
trees, badly blighted, were fumigated with 0.20 
gramme cyanide per cubic foot, for 6 and 10 minutes 
respectively. We could see no bad effects on the 
leaves and no decrease in the blight. In April, 1899, 
after the buds had begun to open, some experiments 
were completed, using 0.20 gramme cyanide, upon 
pear trees. ‘The former tests had been made during 
