68 BULLETIN L377, U. S. DEPARTMENT OF AGRICULTURE 
LITERATURE CITED 
(1) Blackwell, C. P., and Buie, T. S. 
S. C. Agri. Exper. Sta. Bull. 209. 
(2) Columella, Lucius Junius Moderatus. 
Of Husbandry, in Twelve Books; and his book Concerning Trees, 
English translation, London, 1745. 
(3) Gardner, F. D., Noll, C. F., and Lewis, R. D. 
Pa. Agr. Exper. Sta. Bull. 175, 1922. 
(4) Hall, A. D. 
The Book of the Rothamsted Experiments, second edition. 
(5) Hartwell, B. L., and Damon, S. C. 
R. I. Agr. Exper. Sta. Bull. 160. 
(6) Hopkins, C. G., Garrett, F. W., Whitchurch, J. E., and Fahrnkopf, H. F. 
Univ. of 111. Agr. Exper. Sta. Bull. 219, 1919. 
(7) Hutchinson, H. B., and Miller, N. H. J. 
Direct Assimilation of Ammonium by Plants. Rothamsted Memoir, 
Vol. VIII. 
(8) Lawes and Gilbert. 
Rothamsted Memoirs, Vol. V, Fertility. 
(9) 
The Rothamsted Experiments, over 50 years. 
(10) Miller and Krusekopf. 
Manual of the Principal Soils of Missouri, Mo. Agr. Exper. Sta., 1921. 
(11) Miller, M. F., and Hudelson, R. R. 
Mo. Agr. Exper. Sta. Bull. 182, 1921. 
(12) Ohio Agr. Exper. Sta. 
Bull. 336, 1919. 
(13) Ohio Agr. Exper. Sta. publications. 
Bulletins, Nos. 184 and 336. 
Circulars, Nos. 83, 92, 104, 114, 120, 131, and 144. 
(14) Prothero, R. E. 
English Farming Past and Present, 1917. 
(15) Rothamsted Experiment Station publications. 
(a) Lawes and Gilbert, Rothamsted Memoirs, Vol. III. 
(6) Lawes and Gilbert, The Rothamsted Experiments, over 50 years, 
1895. 
(c) Memoranda of the Plan and Results of the Rothamsted Field Re- 
sults, 1855-1889. 
{d) Memoranda of the Origin, Plan and Results of the Field and Other 
Experiments at Rothamsted, 1899-1901. 
(e) The Rothamsted Field Experiments, Plans and Summary Tables, 
1896-1905. 
(J) Rothamsted Experiment Station, Guide to Experimental Plots, 
1906, 1913. 
(g) Rothamsted Experimental Station, Annual Supplement to Guide to 
the Experimental Plots, 1906 ,1907. 
(h) Rothamsted Experimental Station, Annual Report, with the Sup- 
plement to the Guide to the Experiment Plots, 1908-1922. 
(16) 
Report 1921-22. 
(17) Spillman, W. J. 
Distribution of Types of Farming in the United States, U. S. Depart- 
ment of Agriculture Farmers' Bulletin No. 1289. 
(18) Storr-Best, Lloyd. 
Varro on Farming, translation, London, 1912. 
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