E. HoRTOX AND B. S. Salmon 275 



conidiophores persisted to the end of the experiment (14 days). Lime- 

 sulphur at this strength (0-08 per cent, polysulphide sulpliur) appeared 

 to be just breaking down in fungicidal efficiency. 



In the corresponding experiments the same brand of hme-sulphur 

 was used mixed with a solution of calcium caseinate. 



Experiment 14. Lime-sulphur, 1 : 99 (0-16 per cent, polysulphide 

 sulphur) and 1 per cent, calcium caseinate. The solution proved com- 

 pletely fungicidal within 24 hours after spraying; and the same was the 

 case when 0-5 per cent, calcium caseinate was used. 



Experiment 1.5. Lime-sulphur, 1 : 149 (0-11 per cent, polysulphide 

 sulphur) and 1 per cent, calcium caseinate. Complete fungicidal action 

 resulted. 



Experiment 16. Lime-sulphur, 1 : 199 (0-08 per cent, polysulphide 

 sulphur) and 1 per cent, calcium caseinate. On the tenth day after 

 spraying, a few of the mildew-patches had produced fresh, clustered 

 conidiophores, and others, scattered conidiophores; many of the patches 

 were dead. It was clear that at this strength the solution was not quite 

 fungicidal. 



A reference to the hterature of the subject seemed to show that 

 chemists were not in complete agreement as to what chemical compounds 

 constitute the spray-fluid universally known as lime-sulphur (compare 

 Van Slyke, Hedges, and Bosworth(i4); Tartar(i5); Ramsay (16); Thompson 

 and Whittier{i7); Bodnar(i8); Chapin(i9)). The following compounds, 

 which are known or suspected constituents, were tried singly: calcium 

 sulphate, sulpliite, thiosulphate, hydroxyhydrosulphide and polysul- 

 phide (probably pentasulphide). The result of each experiment is given 

 below. 



Materials used. Calcium sulphate. A saturated solution of this salt 

 was prepared by neutrahsing a boiUng solution of 2 grams of pure 

 sulphuric acid in 250 c.cm. of water with a slight excess of carefully 

 purified precipitated calcium carbonate, filtering the hquid and allowing 

 the filtrate to cool. The spray was prepared by mixing the filtrate with 

 enough calcium caseinate solution to give a 1 per cent, concentration of 

 the latter. 



Experiment 32. Calcium sulphate (saturated solution) and 1 per cent. 

 calcium caseinate. Clustered conidiophores were re-formed on all the 

 mildew-patches by the second day, and by the fourth day the patches on 

 the sprayed leaves were as " powdery " as those on the " control " leaves. 

 Calcium sulphite. A solution of 25 grams of crystalhsed sodium 

 sulphite in the minimum amount of water was added to a solution of 



