480 Report of the Mycologist of the 



solution only 24 per cent, rooted, and of cuttings soaked the same 

 length of time in a 1-1000 solution none rooted, while untreated 

 cuttings under entirely parallel conditions, except that they had 

 not been soaked, rooted 76 per cent. Copper sulphate solution as 

 strong as 1-500 does not prevent the germination of rust spores. 



Potassium sulphide is the most promising fungicide tried for 

 soaking cuttings. As previously stated, cuttings soaked one-half 

 hour in potassium sulphide solution, 1-134, rooted a larger per- 

 centage and appeared more vigorous than check. And yet 1-134 

 is more than twenty times the strength required to prevent ger- 

 mination of rust spores. C ^. I : 



In the case of salt, a 1-20 solution was injurious, but a 1-40 

 solution for one hour did no harm. The strength required to 

 prevent spore-germination is not less than 1-45. 



For soaking cuttings it is best to discard all solutions which 

 will not prevent germination of rust spores. Otherwise, the 

 spores which cling to cuttings taken from infested houses might 

 germinate and start the disease, thereby counteracting the good 

 effect of soaking. 



It will be seen that rust appeared on cuttings which had been 

 soaked in potassium sulphide and also on those soaked in salt 

 solution. But this fact should not be considered proof that the 

 treatment had not killed the mycelium in the cuttings. In both 

 cases, forty-eight days intervened between the date of soaking 

 the cuttings and the date on which the plants were examined for 

 rust. This gives ample time for rust pustules to result from in- 

 oculation occuring after the cuttings were soaked. 



An Experiment on Curative Treatment of Rust. 



In order to determine what can be accomplished by curative 

 treatment of rust the following exepriment was made: 



The plants used were, at the beginning, about three inches in 

 height and potted in 2-inch pots. They were of three varieties; 

 viz., Daybreak, Michigan and No. 54, and had been })ropagatod 

 from rusty stock in a house where rust was plentiful. They were 

 divided into four lots and placed under treatment March 4. 



