FUNGICIDES 43 



added, bring to a boil, then pour out the hot solution, 

 straining it through a coarse cloth, and add sufficient 

 water to make exactly five gallons of the solution. This, 

 if correctly made, forms a thick, dark brown, translucent, 

 syrupy solution, which may be preserved as a stock 

 solution. 



For use in treating the sooty mould following the white 

 fly {Aieyrodes citri), dilute this stock solution in the pro- 

 portion of one part to seven parts of water. — Froc. Ninth 

 Ann. Meeting Flo7'ida State Hort. Soc, 1896. 



Fumigation with Hydrocyanic Acid Gas. — Fumiga- 

 tion may be accomplished by placing over the tree a tent 

 of some closely woven material, as 8-ounce duck or 

 drilling. This should be oiled and painted black if the 

 treatment is to be made in daylight. The edges of the 

 tent are held down by a few shovelfuls of earth. For 

 generating the gas, fused 98 per cent, potassium cyanide, 

 commercial sulphuric acid, and water are used, in the pro- 

 portion of I ounce (avoirdupois) of potassium cyanide 

 to I fluid ounce of sulphuric acid and 2 fluid ounces 

 of water. To give the proper concentration of gas, the 

 quantities to be used vary somewhat with the size of 

 the tree. It is estimated that each 180 cubic feet of 

 space enclosed in the tent will require about i ounce 

 of potassium sulphide and the other materials in pro- 

 portion. The water and sulphuric acid are placed 

 together in an earthen vessel in the order named,^ and 

 the vessel is placed under the tent. The potassium 

 cyanide is then dropped in, and the operator quickly 



^ To avoid explosions, the sulphuric acid should always be poured 

 slowly upon the water instead of pouring the water on the sulphuric 

 acid. 



