94 Afinals of Horticulture. 



purple is quickly soluble in water, while Paris green contains 

 no soluble arsenic. Anal3^ses showed that arsenic from London 

 purple entered into the texture of the leaf, while that from 

 Paris green remains entirely upon the surface. Experiments 

 upon plum showed that spraying with London purple so strong 

 as I pound to 200 gallons produced no injury, and the state- 

 ment is made that the supposed injury to plum foliage by the 

 arsenites is really due to a fungus. He also found, as stated 

 before by Cook, that old peach leaves are more susceptible to 

 injury than young leaves. The immunity of the young growth 

 is due to its waxy covering. Injury late in the season is more 

 apparent than early in the season, because of the cessation of 

 growth. A convenient device for producing a spray by com- 

 pressing the end of rubber hose, is described and figured. 

 Woodworth* has made some valuable tests upon the effects of 

 arsenites upon plants. He confirms Bailey's statement that 

 young leaves are less likely to be injured than old ones, and 

 that 'fresh white arsenic produces less injury than any of the 

 other arsenites,' but when the same material is not freshly 

 mixed it is more injurious than the other arsenites. 'Paris 

 green is uniformly less injurious than London purple.' He 

 also finds that some varieties of the same species are more 

 susceptible to injury than others, and he thinks that 'varieties 

 could be produced by selection to which strong poisoning 

 would do no injury.' As a rule, the lower surface of the leaf 

 is more easily injured than the upper surface. Gillette has 

 also made some most valuable experiments with the arsenites f 

 with the view of discovering some method of lessening injury 

 to the foliage. He finds that the addition of milk of lime to 

 Paris green or London purple will almost entirely prevent such 

 injury. As peach is admittedly the most susceptible, the re- 

 sults of this experiment with London purple are most inter- 

 esting in comparison with Bailey's recommendation that it be 

 not used on peach : 



* Bull. 1 1, Ark. Exp. Sta. t Bull. lo, Iowa Exp. Sta. 



