FUNGICIDES. 375 



clover, and lupins had no injurious effect upon the seed, but 

 destroyed, almost completely, the spores of fungi. 



" Formalin" has been used as a preservative for food stuffs, 

 milk, butter, &c.; but since it combines with proteids and also 

 has an inhibitive effect upon enzymes, its use for this purpose 

 is not to be recommended. 



Fungicides. These are in nearly all cases plant poisons, 

 but are used under such conditions or in such dilute solution 

 that they do not injure the higher plants. Some of the more 

 hnportant fungicides are 



Copper salts, v. p. 365. 



Ferrous sulphate, v. p. 378. 



Mercuric chloride. This has been recommended and used 

 in America as a remedy for bunt or stinking smut in wheat. 

 The seed is treated with a O2% solution, conveniently made 

 by dissolving lib. of corrosive sublimate in 50 gallons of w r ater. 



Formaldehyde, v. p. 374. For prevention of bunt in wheat 

 or smut in oats a solution of lib. " formalin" in 50 or 60 

 gallons of water is recommended. The seed is to be soaked 

 for two hours in this solution, which would contain about 

 0-08% of formaldehyde. 



Potassium sulphide. The substance used is generally " liver 

 of sulphur," a dark brown fused mass of sulphide and various 

 poly sulphides of potassium. An American recipe for smut in 

 oats is to soak the grain for 24 hours in a 0*6% solution (i.e., 

 l^H). of potassium sulphide in 25 gallons of water) or for two 

 hours in a 2% solution. 



Hot water. It is possible, in the case of many seeds, to kill 

 the spores of fungi by means of hot water, without injuring 

 the seeds themselves. This is done by dipping them into 

 water at a temperature of about 56 and taking care that every 

 grain is wetted. Ten minutes' treatment is found to suffice 

 for destroying bunt in \vheat or smut in oats. If the grain be 

 soaked for three or four hours in cold water first, five minutes 

 in the hot water is sufficient. For smut in barley the tem- 

 perature should not be higher than 54-5. 



It is said that w r hen grain is treated with hot water or with 

 potassium sulphide there is an increase in the yield greater 



