On the evolution of nitrogen during the growth of plants, and the sources from whence they derive that element

In this communication the author follows up his inquiry into the influence and importance of nitrogen in vegetable physiology, by noticing, in the first place, the experiments of Dr. Daubeny, M. De Saussure, Sir Humphry Davy, and those which he himself has made ; all of which tend to prove that nitrogen is evolved during the healthy performance of the functions of plants; that the proportion which it bears to the oxygen given off is influenced by the sun’s rays; but that owing to the necessary exclusion of the external atmosphere during the progress of the experiments, it is impossible, with any degree of accuracy, to calculate the volume of these evolved gases during any period of the growth of plants in their natural state. If to this indefinite quantity of nitrogen given off by plants there be added that definite volume incorporated into their substance and shown in the author’s former tables, the question arises, whence do plants derive their nitrogen, and does any part of it proceed from the atmosphere ? A problem which the author proposes to solve by a series of tabulated experiments upon seeds, and seedling plants, indicating a large excess of nitrogen in the latter, and under such circumstances of growth that he is compelled to fix upon the atmosphere as its source.