€8 MASSACHUSETTS HORTICULTURAL SOCIETY. 



. Mr. Philbriok asked whether it could be easily decided what 

 fungus causes the disease and how it is disseminated. 



Professor Ma3'nard replied that two species of fungus are found 

 on the leaves of violets, but apparentl}' the disease is caused 

 mainly by one. The spores when mature are exceedinglj' minute — 

 so light as to be thrown off by the slightest motion of the leaf, and 

 remaining suspended in the air a long time they are widely distrib- 

 uted by the varying currents of the wind. 



Benjamin P. Ware asked if he understood the essayist ariglit, 

 that one pound of Paris green to three hundred aud fifty gallons of 

 water was generally the proper mixture to destroy insects without 

 injury to the foliage of trees. In his trials of this remedy he had 

 used only sixty gallons of water to one pound of Paris green, and 

 Jiad seen no injury come to the trees. 



Professor Mayuard said there are many reasons for variations in 

 experience — different conditions of seasons, the weather, the 

 quality of the Paris green, and the chemical character of the 

 water. He had found that one pound of Paris green to three 

 hundred and fifty gallons of water had given fairly good results 

 •on an average. In some cases injury had been done to the leaves 

 by that mixture, but numerous experiments, and analj^ses of the 

 compound as prepared at different times, had led to the adoption 

 of that formula. If the mixture stands a while unused, some of 

 the arsenic may be dissolved in the water and thus render it 

 unsafe. 



Mr. Ware said he had tried to get pure Paris green. Possibly 

 what he had used might have been adulterated, inasmuch as the 

 large quantity used did no harm to the trees, but it destroyed the 

 insects. He had supposed that Paris green was insoluble, and 

 that in the mixture it was only held in suspension. 



Professor Mayuard said that water might contain some 

 ammonia, which would tend to free a portion of the arsenic ; this 

 would dissolve readily in the water and the mixture would become 

 harmful. 



President Spooner referred to the Black Spot fungus {Actiiio- 

 nema rosoe, Fr.) which appeared on the rose leaves in the Durfee 

 Plant House, on the Agricultural College grounds at Amherst, 

 as reported in Bulletin No. 6 of the Hatch Experiment Station, 

 and asked about the sequel of the treatment with the eau celeste 

 compound. 



