PHYSIOLOGICAL EFFECTS ON PLANTS 13 



Eastern orchards were quite different from those in 

 California. With our experiments we did not begin 

 with the deciduous trees until the function of the foli- 

 age had been performed, namely, late in the fall, just 

 previous to the heavy frost. These experiments were 

 conducted in late September and early October. It 

 made little or no difference to us whether we scorched 

 or burned the leaves; our main point was to determine 

 what effect the treatment was going to have upon the 

 fruit or leaf development for the following season. 



The next practical application of the gas was its 

 use for the fumigation of nursery stock. As no pre- 

 cise experiments had been conducted in the Hast, the 

 writer began a series in March, 1897, upon young 

 apple, peach, nectarine, plum, and pear trees. They 

 varied in hight from four to five feet, were thoroughly 

 dormant, and badly infested with the San Jose scale. 

 They were placed in a room 4x7x7^ feet, prepared 

 for the purpose. A general, miscellaneous lot were 

 exposed thirty minutes in gas generated from 0.20 

 gramme of cyanide of potassium per cubic foot of air- 

 space inclosed. Another lot was exposed to gas from 

 0.20 gramme up, through the series formed by adding 

 0.05 gramme each time, until 0.50 gramme was 

 reached. All the trees of these lots were observed 

 very closely for two years. No injury was noticed, 

 and not a living scale was ever detected upon them. 

 The cyanide used in these experiments was the 98-99 

 per cent, pure, while that used at first in the California 

 orchards was the old 58 per cent. ; this must be taken 

 into account when considering the effects of the gas 

 on trees and amounts of chemicals used. 



