PHILOSOPHICAL TRANSACTIONS 
I. On the present Position of the Question of the Sources of the Nitrogen of Vegetation, 
with some new Results, and ‘preliminary Notice of new Lines of Lwestigation. 
By Sir J. B, Lawes, Bart., LL.D., F.R.S., and Professor J, H. Gilbeet, 
LL.D., F.R.S. 
Received, Part 1, July 20, 1887; Parts 2 and 3, May 3, 1888—Read May 17, 1888. 
Contents. 
Introduction 
Page. 
o 
Part I. 
Results relating to other Sources than Free Nitrogen. 
1. Summary of previously published Rotbamsted Results, chiefly relating to Nitric Acid in Soils 
and Subsoils. 3 
2. New determinations of Nitric Acid in Soils and Subsoils. 9 
3. Pei’centage of Nitrogen in the Surface Soils of the Experimental Plots.13 
4. Experiments on the Growth of Red Clover on Bean-exhausted Land.18 
5. Experiments on the Nitrification of the Nitrogen of Subsoils.22 
6. Can Roots, by virtue of their Acid Sajj, attack, and render available, the otherwise insoluble 
Nitrogen of the Subsoil ?.27 
7. Action of dilute Organic Acid Solutions on the Nitrogen of Soils and Subsoils.29 
8. Evidence as to whether Chlorophyllous Plants can take up Complex Nitrogenous Bodies, and 
assimilate their Nitrogen.38 
Part 11. 
Recent Results a7id Conclusions of others, relating to the Fixation of Free Nitrogen. 
1. The Experiments of M. Berthelot . 43 
2. The Experiments of M. Deh^rain .48 
•3. The Experiments of M. Joulie . 53 
MDCCCLXXXIX.—B. B 22.1.89 
