PHYSIOLOGICAL EFFECTS ON PLANTS 19 
condition of the Spy in general appearance was about 
the same as the others, and the buds had just begun to 
swell. The injury, evidently, 
was not due to the gas, as sub- 
sequent tests with normal doses 
showed that no injury to North- 
ern Spy resulted. 
Figure 1 shows one of the York 
Imperial apple trees in this ex- 
periment, fumigated an hour in 
gas representing nearly six times 
the normal strength. The photo- 
graph was taken July 31, 1899. 
The growth was good and the 
tree was in perfectly normal con- 
dition when the experiment was 
closed. 
Plum trees.—Twenty plum 
trees of the following varieties 
were fumigated April 17 and 
18, 1899: Abundance, General 
Hand, Genii, Lombard, Ogon, 
Shipper’s Pride, and Spalding. 
The trees varied in hight from 
2 to 4 feet. Each lot had one J 
hour’s exposure, with 0.35, 0.45, 
Wass 010550: 75,7 1025; 1.35, aud 
1.45 grammes of cyanide. The 
results obtained are very strik- 
FIG. 3—OGON PLUM 
TREE, FUMIGATED 
ing; for instance, there was no damage whatever to 
any varieties until 0.65 gramme was reached, when the 
Spalding had terminals slightly injured, while General 
gparty of the Bureau of Entemelagy, 
U.S, Department of Agriculture, 
