MICHIGAN ACADEMY OF SCIENCE. 227 



TEMPERATURE. 



It was necessary to fix standard temperature for different parts of the 

 experiments. The cultures were grown at a temperature of 28° C. All 

 plantings were made into melted agar cooled to a temperature of 40° C. 

 Room temperature was used at the point at which spore suspensions 

 were exposed to the action of the fungicide. Attention should be called 

 to the fact that the precautions against the variations in the tempera- 

 ture of the spore suspension during tlie exposure, found necessary by 

 Anderson and McClintic are apparently unnecessary in this work. Ordi- 

 nary variations of a few degrees had no effect. The plates were incubated 

 at 28°. 



AGE OF CULTURES. 



The spores of the organisms tested were obtained from cultures on 

 potato agar slants. With G. rufomaculans 4-8 day cultures were tested. 

 Results indicated that there was no difference in the resistance of spores 

 from four-day cultures when compared with those obtained from cultures 

 of eight-day growth. Spores from eight- to fifteen-day cultures exhibited 

 a mucli greater resistance to the fungicides than those obtained from a 

 four- to eight-day incubation. Because of the slower growth and spore 

 production of E. parasitica it was found necessary to use cultures at 

 least eight days old. Cultures of this organism between eight and twelve 

 days' growth were tested but no difference in spore resistance could be 

 detected. A definite standard of five days' growth for G. rufomaculans 

 and ten days for E. parasitica, is recommended. 



FUNGICIDES. 



Copper sulj^hate was selected as the standard compound for the 

 determination of the fungicidal coefficient. This is a stable compound 

 not subject to variation and change due to exposure to air or when 

 greatly diluted. A one per cent solution was first used as approximating 

 the per cent of copper sulphate used in preparing Bordeaux mixture. 

 An extended series of preliminary experiments showed conclusively that 

 a stronger solution was necessary as a basis for dilution. A 10 per cent 

 solution was substituted. With E. parasitica as the test organism a 20 

 per cent solution was found necessary. 



Seven different commercial mixtures of lime sulpliur were used and 

 a dilution of 1-40 made the standard regardless of the Bcaume reading, 

 or chemical composition. The samples of the lime sulphur were secured 

 directly from the company in one gallon lots. In the booklets published 

 by the various companies it was found tliat the dilutions recommended 

 for spray were practically the same. 



