14 SOUECES OF THE NITROGEN OF VEGETATION 



when grown under ordinary field conditions, for then they 

 become collectors of atmospheric nitrogen in virtue of the 

 nodule bacteria with which they are associated. 



REFERENCES 



" Agricultural Chemistry, especially in relation to the Mineral Theory of 

 Baron Liebig." J.R.A.S., 12 (1851), 1. R, Mem., Vol. I., No. 5. " 



"On the Sources of the Nitrogen of Vegetation." Phil Trans., 161 (1861), 

 431. R. Mem., Vol. I. (4to), No. 1. 



"On the Sources of the Nitrogen of Vegetation." Jour. Chem. Soc., 16 

 (1863), 100. R. Mem., Vol. III., No. 1. 



"Sketch of the Progress of Agricultural Chemistry." Rep. Brit. Assn. for 

 1880. R. Mem., Vol. V., No. 13. 



" On the Present Position of the Question of the Sources of Nitrogen of Vege- 

 tation." Phil. Trans., 180, B (1889), 1. R. Mem., Vol. I. (4to), No. 2. 



" Results of Experiments at Rothamsted on the Question of the Fixation 

 of Free Nitrogen." Agricultural Students' Gazette, New Series, 5, 

 1890-91. R. Mem., Vol. VII., No. 1. 



