Studies on Fungicides — III 



57 



In a further series (4 and 5), the action of rain water was compared with 

 that of distilled water, the air being bubbled through the jars for 6 and 

 5 days, respectively. For this purpose fresh rain water was collected. 

 In these tests bordeaux mixture (4-4-50) was used. One bordeaux prepara- 

 tion was made as usual with distilled water, while in a second preparation 

 rain water was used instead. The set-up was similar to that of the former 

 series. There were four combinations — distilled-water bordeaux with 

 distilled water, rain-water bordeaux with distilled water, distilled-water 

 bordeaux with rain water, and rain-water bordeaux with rain water. A 

 second set in open petri dishes was maintained as before. Chemical 

 tests before and after showed no signs of free copper. The results of the 

 germination tests with the filtrates, using conidia of Sclerotinia america?ia, 

 are recorded in table 10. 



TABLE 10. Percentage Germination of Sclerotinia Americana Conidia in Filtrates 

 from Rain Water and from Distilled Water, on Bordeaux Mixtures Exposed to 

 Various Treatments 



Discussion. The results presented in table 9 show that the continued 

 passage of air through distilled water standing on bordeaux mixture or 

 copper-lime does not promote the solution of copper any more than where 

 the water is left undisturbed. The lower percentages of germination 

 obtained in experiment 3 cannot be explained. 



