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Peronospora infestans iu a clear glass jar, and allowed it to ferment. 

 After the lapse of two months a mold, or mildew, formed on its sur- 







4 



^cale 



face. Placing a small portion of this on a glass slide six inches long by 

 two inches wide I inclosed the latter in a jar containing about an 

 ounce of distilled water, and secured its contents with a ground-glass 



