MEMOIR 143 DECEMBER, 1932 



CORNELL UNIVERSITY 

 AGRICULTURAL EXPERIMENT STATION 



STUDIES ON THE DOWNY MILDEW OF ONIONS, 



AND THE CAUSAL ORGANISM, 

 PERONOSPORA DESTRUCTOR (BERK.) CASPARY 



HAROLD THURSTON COOK 



ITHACA, NEW YORK 

 PUBLISHED BY THE UNIVERSITY 



Received for publication May 3, 1932 



