G-212 



BY 



J. ARTHUR HARRIS AND C. S. SCOFIELD 



Reprinted from JOURNAL OF AGRICULTURAL RESEARCH 



Vol. XX, No. 5 : : : : Washington, D. C., December 1, 1920 



PUBLISHED BY AUTHORITY OF THE SECRETARY OF AGRICULTURE, WITH 

 THE COOPERATION OF THE ASSOCIATION OF LAND-GRANT COLLEGES 



WASHINGTON : GOVERNMENT PRINTING OFFICE : 1920 



