PHYSIOLOGICAL EFFECTS ON PLANTS 



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 i 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 

 1 8, 1899 : Abundance, General 

 Hand, Genii, Lombard, Ogon, 

 Shipper's Pride, and Spalding. 

 The trees varied in hight from 

 2 to 4 feet. Bach lot had one 

 hour's exposure, with 0.35, 0.45, 

 0.55, 0.65, 0.75, 1.25, 1.35, and 

 1.45 grammes of cyanide. The 

 results obtained are very strik- 

 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 



FIG. 3 OGON PLUM 

 TREE, FUMIGATED 



