71 



of the four experiments above mentioned — one with the California 

 wash and one with the Oregon wash — were begun March 3, and 

 the other two (in which also both washes were used) were begun 

 March 5. The tent experiment was begun on the 21st of the 

 month. Almost daily observations on the lots treated were con- 

 tinued until March 25; that is twenty-two days for the first two 

 lots, twenty days for the third and fourth, and five days for the lot 

 under tents. A careful examination was made May 12, ten weeks 

 after the first trees were sprayed, and a final inspection August 20, 

 more than five months after the time of treatment. 



The experiments consisted of a single application of the insec- 

 ticide in every case, with varying subsequent treatments of the 

 different trees with water. Frequent counts of dead and living 

 scales were made for all of the trees, no attention being paid 

 in these counts to old dead scales, but only to those whose size 

 and immature character showed that they belonged to the new 

 generation of the preceding fall. Counts of dead and living scales 

 were made in all cases either before or shortly after the application 

 of the insecticide spray. It was in this way ascertained that an 

 average of about fifty per cent, of the immature scales were al- 

 ready dead on these trees before the insecticide was applied; and 

 that the action of the insecticide was scarcely perceptible within 

 the first twenty-four hours. 



Experimental Trees Used. 

 P^orty-three trees were used in all the experiments, twenty-five 

 of them apple-trees and eighteen peach. They varied in height 

 from twelve to eighteen feet; in spread of top from eight to twenty 

 feet; and in diameter of trunk from four to nine inches. The av- 

 erage height was fourteen feet, and the average, spread, thirteen. 

 The general condition of these trees varied from "very poor" to 

 "excellent," six of them being described as "very poor," eight as 

 "poor," sixteen, as "fair," ten, as "good," and three, as "excel- 

 lent." Some of the peach-trees were more than half dead, and many 

 of them in such a condition that the owners were about to remove 

 them. The dry weather of the preceding summer had killed the 

 young growth even on otherwise healthy trees, and in some cases 

 much of the older wood had also died from drouth. All the trees 

 were, of course, infested with the San Jose scale, eighteen of them 

 badly so, and the others to a medium degree. 



Weather of the Period. 

 The weather of the experimental period was the ordinary vari- 

 able weather of an Illinois March, the temperature at seven o'clock 



