Vol. XX JANUARY 3, 1921 No. 7 



JOURNAL OF 



AGRICULTURAL 

 RESEARCH 



CONTENTS 



Page 



Fusarium-Wilt of Tobacco ------ 515 



JAMES JOHNSON 



(Contribution from Bureau of Plant Industry and Wisconsin Agricultural 

 Experiment Station) 



Sugar Beet Top Silage ------- 537 



RAY E. NEIDIG 



(Contribution from Idaho Agricultural Experiment Station) 



Nodule Bacteria of Leguminous Plants - 543 



F. LOHNIS and ROY HANSEN 



( Contribution from Bureau of Plant Industry and Illinois 

 Agricultural Experiment Station) 



Correlation and Causation - - - - - 557 



SEWALL WRIGHT 



(Contribution from Bureau of Animal Industry) 



Measurement of the Amount of Water That Seeds Cause 

 to Become Unfree and Their Water-Soluble Material - 587 



GEORGE J. BOUYOUCOS and M. M. McCOOL 



(Contribution from Michigan Agricultural Experiment Station) 



PUBLISHED BY AUTHORITY OF THE SECRETARY OF AGRICULTURE, 



WITH THE COOPERATION OF THE ASSOCIATION OF 



LAND-GRANT COLLEGES 



WASHINGTON, D. C. 



WASHINGTON : GOVERNMENT PRINTING OFFICE i 1(31 



