154 THE HOP. 



5. Under the assumption that sulphur has some 

 specific action upon the fungus, various soluble com- 

 pounds containing the ingredient are employed, chiefly 

 the sulphides of sodium, calcium, and potassium 

 ("liver of sulphur"). These substances are, undoubt- 

 edly, of considerable use in checking and destroying 

 molds of all kinds. They are readily soluble in water, 

 and are generally applied in the ordinary washes of 

 soft soap and quassia at the rate of i^ or two pounds per 

 100 gallons of wash. A wash of this description, fol- 

 lowed by an application of powdered sulphur, is per- 

 haps the most effective and safe means known at present 

 for an attack of mold. The alkaline sulphides in solution 

 do not keep well, unless air is excluded from the ves- 

 sels in which they are kept. Practically all mold 

 washes have, as a basis, one or more of the above sul- 

 phides in conjunction with substances like glycerine, 

 which tend to keep the wash upon the leaf till it has 

 done its work, and which also prevent too rapid oxi- 

 dation of the active ingredient. Although the prepara- 

 tion of washes is not difficult, a certain amount of 

 chemical and botanical knowledge is essential to avoid 

 damaging the plants, and until this is obtained it is 

 perhaps the wisest plan to obtain chemicals or 

 washes prepared ready for use from experienced 

 manufacturers. 



Many other substances, notably preparations of 

 copper (Bordeaux mixture, "Fostite," talc and finely 

 powdered copper sulphate), have a more certain effect 

 in destroying mold, but the application to hops is 

 scarcely feasible on account of their somewhat poison- 

 ous properties. 



There are various definite chemical and physical 

 differences between the cells and cell-walls of the hop 

 leaf and the substance of "mold" fungus, and it should 

 be possible to construct a wash or fungicide dependent 

 upon these differences. This, however, remains to be 



