A Study of Meadow-Crop Diseases in New York 



85 



In one experiment a spore suspension in distilled water was atomized 

 on two-months-old timothy seedlings in pots in the greenhouse, and the 

 pots were placed in a moist chamber for forty-eight hours. Seven days 

 later small light-brown spots had begun to appear on inoculated leaves. 

 Within two days the spots had become more typical, showing the light 

 straw-colored center and the purple margin. 



Although no definite data are at hand on secondary cycles, the spores 

 doubtless are carried by rain and wind from plant to plant during the 

 growing season, giving rise to new lesions. 



Control 



Since the fungus has been shown to germinate practically as well at 3° 

 as at 25° C. if time enough be allowed, it should serve as a most satisfactory 

 organism with which to test the common opinion that the action of sulfur 

 depends upon its volatilization at high temperatures. Barss' statement 

 (1926) that " hot weather is believed to be essential in getting a thorough 

 control with sulfur dust since the heat causes the sulfur to volatilize and 

 give off fumes which kill the fungus and its spores " has been cited already 

 under the discussion of powdery mildew of clover. To test this hypothesis, 

 spores of H. phlei were germinated in contact with sulfur in two experi- 

 ments each in duplicate at various temperatures to see if the toxicity of 

 the sulfur varied with the temperature. The results of these two experi- 

 ments appear in table 23. 



