78 



(17) Shedd, 0. M. 



1914. The relation of sulphur to soil fertility. Ky. 

 Agr. Exp. Sta. Bui. 188, p. 593-630. 



(18) Skinner, J. J., and Sullivan, M. X. 



1914. The action of manganese in soils. U. S. Dept. 

 Agr. Bui. 42, 32 p. 



(19) Skinner, J. J., and Reid, F. R. 



1916. The action of manganese under acid and neutral 

 soil conditions. U. S. Dept. Agi'. Bui. 441, 12 

 p., 3 fig. 



(20) Truog, E. 



1916. The utilization of phosphates by agricultural 

 crops, including a new theory regarding the 

 feeding power of plants. Wis. Agr. Exp. Sta. 

 Resh. Bui. 41, 50 p. 



(21) White, J. W. 



1913. The results of long continued use of ammonium 



sulphate upon a residual limestone soil of the 

 Hagerstown series. In Pcnn. State Col. Rept. 

 1912-1913, p. 55-104, 9 pi. 



(22) White, J. W. 



1914. Concerning the growth and composition of clov- 



er and sorrel (Rumex acetosella) as influ- 

 enced bv various amounts of limestone. In 

 Penn. State Col. Rept. 1913-1914, p. 46-80, 4 pi. 



(23) White, J. W. 



1915. Continued studies in acid soil from the ammon- 



ium sulphate plots. In Penn. State Col. Rept. 

 1914-1915, p. 86-104, 3 pi. 



