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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 John Bennet 
LuWES, F.B.S., F.C.S., Joseph Henry Gilbert, Ph.I)., F.B.S., F.C.S., and Evan 
Pugh, Ph.l)., F.C.S. 
Eecelred June 21, — Bead June 21, 1860. 
CoJTTEIfTS. 
PAET FIRST. 
GEXEEAL HISTOET, AXD STATEMENT OE 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 land 435 — 438 
B. Yield of Nitrogen per acre when Wheat is grown in alternation with Beans, 
or with EaUow 438 — 439 
C. Yield of Nitrogen per acre when crops are grown in an actual course of Eotation 439 — 440 
D. Eolation 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. Boussingault 448 — 455 
B. The Experiments of M. G. Ville 455 — 463 
Summary statement of the Eesults, and conclusions, of M. Botxssingattlt, and 
M. G. ViLLE 463 — 464 
C. The Experiments of M. Mene 464 
D. The views of M. Eov 464 — 465 
E. The Experiments of MM. Cloez and Gratiolet 465 
F. The Experiments of M. De Luca 465 — 466 
G. The Experiments of M. IIarting 466 
II. Experiments recorded by M. A. Petzuoldt 467 
Concluding observations 467 — 468 
PART SECOND. 
EXPEEIMENTAL EESULTS OBTAINED AT EOTHAMSTED, DUEING THE YEAES 1857, 
1858, AND 1859. 
Introductory observations 468 — 470 
Section I. — Conditions repaired, and Plan adopted, in Fxperi/ments on the Question of the assi- 
milation of Free Nitrogen by Plants -. — 
A. I’reparation of the soil, or Matrix, for the reception of the Plant, and of the 
nutriment to be supplied to it 470 — 472 
3 0 
MDCCCLXI. 
