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XXIII. On the Sources of the Nitrogen of Vegetation; with special reference to the 

 Question whether Plants assimilate Free or uncombined Nitrogen. By Jonx B-ennet 

 Lawes, F.B.S., F.C.S., Joseph Henry Gilbert, Ph.D., F.B.S., F.C.S., and Evan 

 Pugii, Ph.D., F.C.S. 



Received June 21,— Bead June 21, 1SG0. 

 YORK- 



Contents. 

 GARDEN 



PART FIRST. 



GENERAL HISTORY, AND STATEMENT OF THE QUESTION. 



Page 



Section I. — Introduction, and early History 433 — -435 



SECTION II. — Annual yield of Nitrogen per acre, in different Crops: — 



A. Yield of Nitrogen per acre when the same crop is grown year after year, on 



the same laud 435 — 43S 



B. Yield of Nitrogen per acre when Wheat is grown in alternation with Beans, 



or with Fallow 438—439 



C. Yield of Nitrogen per acre when crops are grown iu an actual course of Rotation 439 — 440 



D. Relation of the increased yield of Nitrogen in the produce, to the amount sup- 



plied, when nitrogenous manures are employed 440 — 442 



Section III. — General view of the various actual or possible sources of the Nitrogen of our crops : — 



Enumeration of, observations, &c 442 — 447 



Section IV. — Review of the Researches of others, on the question of the assimilation of Free 

 Nitrogen by Plants, and on some allied points : — 



Introductory observations ". 447 



A. The Experiments of M. Bocssingault 44S— 455 



B. The Experiments of M. G. Ville 455— 4G3 



Summary statement of the Results, and conclusions, of M. Boussingault, and 



M. G. Villb 463—464 



C. The Experiments of M. Mene 464 



D. The views of M. Rot 464—465 



E. The Experiments of MM. Cloez and Geatiolet 465 



P. The Experiments of M. De Luca 465—466 



G. The Experiments of M. Hartinq 466 



II. Experiments recorded by M. A. Petzuoldt 467 



Concluding observations 467 — 168 



PART SECOND. 



EXPERIMENTAL RESULTS OBTAINED AT ROTHAMSTED, DURING THE YEARS 1857, 



1858, AND 1S59. 

 Introductory observations 46S — 170 



Section I. — Conditions required, and Plan adopted, in Experiments on the Question of the assi- 

 milation of Free Nitrogen by Plants: — 

 A. Preparation of the soil, or Matrix, for the reception of the Plant, and of the 



nutriment to be supplied to it 470 — 472 



<* MDCCCLXI. 3 



