3^ 



fungus. Remains of lettuce plants infected with the disease were 

 buried just beneatli the surface in pots of soil and thoroughly 

 exposed to the gas. After several hours they were taken out and 

 placed in the greenhouse, where the fungus immediately started into 

 growth and developed luxuriantly upon the soil, showing not the 

 slightest effect from the gas. One of our greenhouses was treated 

 with this gas at the following rate : i oz. of potassium cyanid, i oz. 

 of sulphuric acid and 3 oz. of water to 150 cu. ft. of space, with the 

 result, that no kind of fungi either in the soil or upon the plants was 

 affected. From these results it may be concluded that hydrocyanic 

 gas has considerable value for fumigating a house between crops 

 and killing insects and fungi where exposed to its action, but as a 

 fungicide to be used with living plants or for the control of the Drop 

 fungus, it has no value whatever. 



FORMALDEHYDE GAS. 



This gas was chosen for experiment on account of its rapidly 

 increasing use as a germicide and disinfectant. It results from the 

 imperfect combustion of wood alcohol, and is produced by burning 

 the latter substance in a lamp made especially for the purpose. 

 Several different makes of these lamps are in the market. In these 

 experiments a single burner '' Moffatt " lamp, presented by E. Lilly 

 & Co., Indianapolis, Ind., was used. Larger sizes and various 

 styles are made by the same company. Spores of Botrytis were not 

 entirely prevented from germination when exposed sixty minutes to 

 formaldehyde gas in the case used in the last experiment. Tube 

 cultures of the Drop fungus when exposed for several hours under 

 the same conditions were killed. A test was also made by burning 

 the lamp for tweJve hours in a portion of a greenhouse in which 

 there was a bench of carnations considerably affected by rust, the 

 space area being within the capacity of the lamp. Subsequent tests 

 showed that the rust spores germinated freely and apparently were 

 not at all injured. Beneath the surface of the soil the same results 

 appeared as with cyanid gas ; namely no effect. With exposure of 

 twelve hours in the small tight case it could not be seen that the gas 

 had the slightest effect beneath the surface. Plainly therefore this 

 gas has no practical value as a fungicide for these organisms. 



