Studies on Fungicides — II 23 



are listed the results of three experiments on the effect of sulfur dust on 

 the conidia of Venturia tnaequalis. This gives an indication of the varia- 

 tion obtained between experiments performed at different times. 



SUMMARY 



1. The practicability, advantages, and limitations of laboratory tests 

 for fungicides are discussed. It is believed that such tests are reliable 

 and significant. 



2. A method for testing developed at the Laboratory of Plant Pathology 

 at Cornell University is described. Briefly, the technic is as follows: 

 Glass slides are sprayed or dusted with the fungicide to be tested, and 

 are then placed in inverted moist chambers. The spores of the fungus 

 are suspended in water, and drops of this suspension are placed on the 

 sprayed or dusted slides and on the check slides. The moist chamber is 

 sealed with water, giving a highly saturated atmosphere in which the 

 spores are left to germinate at the desired temperature. After a given 

 time, counts are taken to determine the percentage and the type of 

 germination. 



3. The necessity for standardization of the conditions for germination 

 and the factors relative thereto, such as the source and age of spores, type 

 of water, spore-suspension concentration, oxygen relations, temperature, 

 light, and time, is discussed. 



4. Details concerning methods of applying the fungicides and the 

 recording of data are presented. 



REFERENCES CITED 



Clark, J. F. On the toxic effect of deleterious agents on the germination 

 and development of certain filamentous fungi. Bot. gaz. 28:289- 

 327, 378-404. 1899. 



Doran, Wm. L. Effect of external and internal factors on the germina- 

 tion of fungous spores. Bui. Torrey Bot. Club 49:313-340. (Or, 

 New Hampshire Agr. Exp. Sta., Sci. contrib. 19:313-340. 1922.) 

 1922. 



Duggab, B. M. Physiological studies with reference to the germination 

 of certain fungous spores. Bot. gaz. 31:38-66. 1901. 



Kightlinger, C. V. Preliminary studies on the control of cereal rusts 

 by dusting. Phytopath. 15:611-613. 1925. 



Lee, II. Atherton, and Martin, J. P. A method for testing in vitro 

 the toxicity of dusl fungicides to fungous spores. Phytopath. 17:315- 

 319. 1927. 



