Hoagland — 24 — Plant Nutrition 



In concluding, I can only express the hope that I have 

 established an introduction for the somewhat more 

 specialized discussions to follow. 



REFERENCES :- 



BURD, John S. Rate of absorption of soil constituents at suc- 

 cessive stages of plant growth. Journal of Agricultural 

 Research 18: 51-72, 1919. 



and Martin, J. C. Water displacement of soils and 



the soil solution. Journal of Agricultural Science 13: 265- 

 295, 1923. 



Secular and seasonal changes m the 



soil solution. Soil Science 18: 151-167, 1924 



Cummins, Arthur B. and Kelley, Walter P. The formation 

 of sodium carbonate in soils. California Agricultural Ex- 

 periment Station, Technical Paper 3: 1-35, 1923. 



Davis, A. R. The variability of plants grown in water culture. 

 Soil Science 11 : 1-32, 1921. 



and Hoagland, D. R. An apparatus for the growth of 



plants in a controlled environment. Plant Physiology 3: 

 277-292, 1928. 



Hendricks, S. B. and Fry, W. H. The results of x-ray and 

 microscopic examinations of soil colloids. Soil Science 29: 

 457-479, 1930. , , . ^ . 



Hoagland, D. R. The freezing-point method as an index of 

 variation in the soil solution due to season and crop growth. 

 Journal of Agricultural Research 12: 369-395, 1918. 



Jenny, H. Factors of soil formation. McGraw-Hill, New 

 York 1941. 



Kelley, W. P. The reclamation of alkali soils. Calif. Agr. Exp. 

 Sta. Bulletin 617, 1937. 



and Thomas, E. E. The removal of sodium carbonate 



from soils. Univ. of Calif. Agr. Exp. Sta. Technical Paper 

 1 : 1-24, 1923. , 



and Brown, S. Melvin. Replaceable bases m soils. 



Calif. Agr, Exp. Sta. Technical Paper 15 : 1-39, 1924. 



, DoRE, W. H. and Brown, S. M. The nature of the 



base exchange material of bentonite, soils, and zeolites, as 

 revealed by chemical investigation and x-ray analysis. Soil 

 Science 31: 25-55, 1931. „ ,, „ ^ .• 



, Jenny, Hans and Brown, S. M. Hydration of mm- 



erals and soil colloids in relation to crystal structure. Soil 

 Science 41 : 259-274, 1936. 



, Woodford, A. O., Dore, W. H. and Brown, S. M. 



Comparative study of the colloids of a Cecil and Susque- 

 hana soil profile. Soil Science 47: 175-193, 1939. 

 Parker, F. W. Methods of studying the composition and con- 

 centration of the soil solution. Soil Science 12: 209-232, 



1921. .... 



Richards, L. A. A pressure membrane extraction apparatus 

 for soil solution. Soil Science 51 : 377-386, 1941. 



