QUESTION OF THE SOURCES OF THE NITROGEX OF VEGETATION. 
79 
soil under the influence of porous and alkaline bodies. We shall refer to the point 
again in our concluding remarks, but we may here say in passing, that the results of 
our experiments on the growth of wheat for many years in succession on the same 
land without nitrogenous manure, show that with much less nitrogen annually 
removed in the crops, and estimated to be lost by drainage, than would be required 
for the growth of the Leguminosee in Wolff’s experiments, the soil has nevertheless 
lost much nitrogen. Again, taking the average of ten years, the amount of nitrogen 
as nitric acid which has passed through 60 inches depth of soil and subsoil in the 
Rothamsted drain-gauges, exposed to the air and rain, with aeration from below also, 
but without vegetation, ha,s been somewhat less than 40 lbs. per. acre (= 44’8 kilog. 
per hectare) annually; and it cannot be doubted that at least the greater part of this 
has been derived from the organic nitrogen of the soil and subsoil. It is obvious, 
therefore, that the amount due to absorption and to such fixation together, must be 
much less than this, 
If, therefore, neither nitrogenous impurity in the sand, nor accidental sources of 
combined nitrogen, can be supposed to account for the gains by the Leguminosm in 
Wolff’s experiments, it would seem that the explanation must be sought, either in 
the agency of micro-organisms, or in direct assimilation by the plants themselves. 
8. The Experiments of Professor W. O. Atwater. 
Professor Atwater, of the Wesleyan University, Middletown, Conn., U.S.A,, has 
published three papers in the ‘ American Chemical Journal’:—1. “ On the Acquisition 
of Atmospheric Nitrogen by Plants ” (vol. 6, No. 6); 2 (with P. W. Pockwood). On 
the Loss of Nitrogen by Plants during Germination and Growth” (vol. 8, No. 5); 
3. “ On the Liberation of Nitrogen from its Compounds and the Acquisition of 
Atmospheric Nitrogen by Plants ” (vol. 8, No. 5). In these papers he gives the 
results of experiments of his own, and discusses the results of others also, on various 
aspects of the question. In what years his experiments were made is not stated, but 
we assume in 1883 and 1884, as they were undertaken after a visit he paid to Europe 
in 1882, and in the autumn of 1884 he gave a paper on the subject, at the meeting of 
the British Association at Montreal, and also at the meeting of the American 
Association at Philadelphia. 
It is stated that the question was :—“ May plants, grotvn under normal conditions, 
acquire any considerable amount of nitrogen, free or combined, from the ambient 
atmosphere ? ” It is further stated, that after a series of trials had shown a not 
inconsiderable acquisition of atmospheric nitrogen, a second series was planned to 
verify the results of the first, and to include a collateral inquiry, namely :— 
“ Mow is the acquisition of nitrogen from the atmosp)here affected by abnormal 
conditions of growth, and ivhat bearing may the results obtained have upon the inter- 
2 yretation of those obtained by other exqyerimenters, and upon the genercd question of 
the assimilation of atmosptheric nitrogen by plants f ” 
