U. S. DEPARTMENT OF AGRICULTURE, 
BUREAU OF PLANT INDUSTRY—BULLETIN NO. 186. 
B. T. GALLOWAY, Chief of Bureau. 
FIELD STUDIES OF THE CROWN-GALL AND 
HAIRY-ROOT OF THE APPLE TREE. 
BY 
GEORGE G. HEDGCOCK, 
PATHOLOGIST, FRUIT-DISEASE INVESTIGATIONS. 
IssuED NOVEMBER 17, 1910. 
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WASHINGTON: 
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