J. V. Eyre, E. S. Salmon and L. K. Wormald :307 



of precipitated sulphur, a quantity of Solution XI was diluted with a 

 known volume of water and the correct amount of weak hydrochloric 

 acid added to neutralise the" liquid and precipitate the polysulphide 

 sulphur. This liquid was then made up to the same volume as that 

 of the diluted unaltered Solution XI. The liquid containing the very 

 finely precipitated sulphur was well shaken before being used and was 

 sprayed on mildewed leaves at the same nodes as leaves spra3'ed with 

 the clear No. XI solution. Both liquids were found to be equally 

 fu7igicidal. This experiment was repeated and the same result was 

 obtained. Although this suggests that the precipitated sulphur has 

 some action on the fungus it does not aflord satisfactory evidence that 

 the precipitated sulphur alone was responsible for the fungicidal action 

 because ammonium chloride was present in the Uquid after precipitation. 

 This amount of ammonium chloride, namely, 0-28 %, has been found 

 to have a .severe checking action on the fungus. (See Table 4.) Further 

 work in this direction is in progress. 



Summary. 



1. The rosi.«tance of the hop-mildew (Sp/iaerolhern HviiinU (DC.) 

 Burr.) to polysulphide solutions varies according to its stage of develop- 

 ment. The earliest stages after infection and antecedent to the produc- 

 tion of conidiophores are the most resistant, requiring approximately 

 a solution of double the concentration lethal for the "powdery" conidial 

 stage. The "powdery" conidial stage occurring on young leaves is more 

 resistant than the same stage on older leaves. 



2. Conclusive proof has been obtained that with polvsulphide 

 solutions neither the total sulphur content nor the sulphide sulphur 

 content gives an index of their fungicidal value. 



3. The percentage of polysulphide sulphur in polysulphide solutions 

 appears to be the factor determining their fungicidal value. 



4. The fungicidal value of such solutions does not depend upon the 

 nature of the polysuJphides present. 



{Received March 6th, 1919.) 



