6 



adults, doubtless tlie earliest to enieige, were already bejjiniiinjj to die 

 si)ontaueously. The experiment was eontiuued tor eigbt days, when all 

 the curculios of the first lot were dead, and nearly all of the other 

 poisoned lots, a fourth of the eueck having also perished. 



London imrple cxpenment, May 17, 1889. 



EFFECT ON THE FOLIAGE. 



It is well known to fruit-growers that the leaves of the peacli are 

 n)ucli more sensitive to the scorching effect of the arsenical poisons 

 than those of the ai)ple or plum, and it is important to know just how 

 strong a mixture of the common arsenical insecticides that tree will 

 bear under favorable, and also under unfavorable, conditions. My 

 experiments on this point are incomplete, but they are given here for 

 what they are worth: 



First. Two branches of a iieach tree were sprayed May 18 with Lon- 

 don purple mixtures, a pound to 100 and a jjound to -!()0 gallons, re- 

 spectively. A week later no noticeable difference could be made out 

 between the condition of the two branches, the tips of the leaves in 

 both being somewhat deadened and dry. May 20 identical apjdica- 

 tions were made, with no apparent effect on the foliage by May 22. 

 Heavy rains followed, and no further observations were made. 



June two other branches were sprayed as before. A heavy rain 

 followed June 8, and more upon the 9tli. On the 10th the effects of 

 the i)oison were somewhat apparent on both branches, reddish discol- 

 orations occurring where the fluid had gathered in drops and also along 

 the margins of the younger leaves. Further rains occurred on the IGth 

 and 17tb. On the 18th the discolored spots had increased in size, 

 those on the branch sprayed with the stronger solution being somewhat 

 larger and more numerous. No leaves had fallen, but those worst 

 affected were easil}' detached, and doubtless would have fallen event- 

 ually. This loosening of the leaves was evidently due, not to damage to 

 the petiole, but to premature ripening of the leaf,* consequent on the 

 chemical injury to the blade. June 8 two other branches were sprayed 



* Ascertained by studying sections of the petiole. 



