[Vol. 6 



42 



ANNALS OF THE MISSOURI BOTANICAL GARDEN 



theories, and it has the advantage of being less roundabout; 



I 



that is, the need of phosphates and the avoidance of an acid 

 reaction are requirements of the culture medium, known be- 

 yond any doubt. It seems that the various ramifications of 

 these known factors must be studied in detail before specula- 

 tions in regard to * ' auximones ' ' and "rare nutrients' ' be 

 entered into widely. 



This investigation was supported in part by the Ohio Agri- 

 cultural Experiment Station (Adams Fund Project), in part 

 by the Graduate Laboratory of the Missouri Botanical Gar- 

 den, and in part by the Department of Biological Chemistry 



of Medicine. 



The 



of the Washington University School 

 author wishes to express his indebtedness to Professor B. M. 

 Duggar for many helpful suggestions and for constant encour- 

 agement throughout the progress of this work. 



Bibliography 



Allen, E. R. ('15). The determination of nitric nitrogen in soils. Jour. Ind. 

 and Ener. Chem. 7 : 521-529. f. 1-2. 1915. 



, and Bonazzi, A. ('15). On nitrification. I. Preliminary observations 



Ohio Agr. Exp. Sta., Tech. Bui. 7 : 42 pp. f. 1-6. 1915. 



; and Davisson, B, S. ('19). An all-glass nitrogen apparatus. Ann. Mo 



Bot. Gard. 6 : 45-48. pi. 2. 1919. 



Bonazzi, A. ('15). Cytological studies of Azotobacter chroococcum. Jour. Agr 

 Res. 4 : 225-240. pi. 31-33. 1915. 



•, ('19). On nitrification. II. Intensive nitrification. Jour. Bact. (In 



press. ) 



— , ('19a). ibid. III. Morphological studies of the nitrite- forming bac 



teria. Bot. Gaz. (In press.) 



Bottomley, W. B. ('14). Some accessory factors in plant growth and nutrition 

 Roy. Soc. London, Proc. B88 : 237-247. 1914. 



, ('15). Bacterial test for plant food accessories (auximones). Ibid 



B89 : 102-108. 1915. 



■, ('17). The isolation from peat of certain nucleic acid derivatives. 



ibid. B90 : 39-44. 1917. 



Clark, W. M., and Lubs, H. A. ('17). Colorimetric determination of hydrogen 

 ion concentration and its application in bacteriology. Jour. Bact. 2 : 1-34, 



109-136, 191-236. f. 1-8. 1917. 



Davisson, B. S. ('16). Titrametric determination of nitrites. Am. Chem. Soc., 

 Jour. 38 : 1683-1687. f. 1. 1916. 



