Spraying Apple Orohabds in a "Wet Season. 391 



sulpliate of copper and calcium. It seems that a sm^all amount of 

 copper is held in solution in this last form, one rich in the sulphate 

 of copper. 



"A number of experimentis have also been made to determine 

 which of the copper salts found in the Bordeaux mixture can be 

 dissolved by atmospherici agents. 



"The hydra^je of copper was separa/ted as already described, 

 and thoroughly washed. It was then put into a small amount of 

 distdlled water. Through this mixture a stream of dried carbonic 

 acid gas was passed for a few minutes and the liquid was again 

 filtered. The filtrate, when tested for copper, revealed consider- 

 able quantities of the metal. After a short time the solution 

 became turbid and soon deposited almost all the dissolved copper, 

 undoubtedly because of the rapid decomposition of the bicarbonate 

 which had formed at fii^it. 



" Similar experiments were made with the basic sulphate, after 

 it had been entirely freed from the sulphate of calcium and thor- 

 oughly washed. It was then treated with a solution of the 

 hydrate of potash. Cai'bonic acid gas was again applied, and in 

 this case it caused the solution of much greater amounts of the 

 copper. The filtrate in addition showed also a remarkable quan- 

 tity of sulphuric acid. The liquid again became turbid, but much 

 larger quantities of copper remained in solution. It seems to 

 me that this circumstance can be explained by admitting that 

 the carbonic acid gas acted upon the basic sulphate causing the 

 formation of the carbonate of copper, which in part remained 

 insoluble, and in part passed into solution on account of the pres- 

 ence of the gas, and the sulphate of copper. 



" Copper in the form of the sulphajte should be more ef&cacious 

 than when it is precipitated as a hydrate, but the conditions 

 which would cause a larger amount of it to be formed must stiUl 

 receive careful study." 



SUMMARY. 



1. The apple-scab fungus, Fusicladium dendriticum, attacks 

 apple trees very early in the season, even before the petals fall to 

 the ground. (Pages 362, 365.) 



