THE SOURCES OF THE NITROGEN OF VEGETATION, ETC. 485 



of the action of the sun's rays, by virtue of which carbonic acid is decomposed, and 

 oxygen evolved. Or, it may result from other causes, to which we shall refer pre- 

 sently. 



In order to ascertain how far the presence of Ozone within the plant may have a 

 bearing upon the point at issue, we have attempted to solve, by experiment, the follow- 

 ing questions : — 



1. Is there, during the growth of plants, Ozone within the cells or intercellular pass- 

 ages 1 



2. If Ozone be present within the structures of the plant, is it in circumstances in 

 which it would be likely to oxidize free Nitrogen into any of its oxygen compounds \ 



3. Is Nitric acid present in the living cells of any plant of which it is not a natural 

 product of growth ? 



In a number of experiments which we have made upon the gases obtained by exhaust- 

 ing plants placed in water freed from air by boiling, no Ozone was perceptible. An- 

 other series of experiments upon the oxygen evolved from plants immersed in water 

 saturated with carbonic acid gave similar results. 



In the latter series about 1 ounce of the green plant was placed in 500 cub. cents, of 

 carbonated water, and the whole subjected to sunlight. The decomposition of carbonic 

 acid commenced almost immediately, and the evolution of gas was rapid. In this way 

 100-200 cub. centims. of gas were obtained,. which contained sufficient oxygen to inflame 

 a glowing taper ; yet no trace of Ozone was manifested on placing test-paper in the gas. 

 That evolved from Wheat, Barley, Oats, Beans, and Clover behaved alike in this 

 respect. Granting that these experiments may not be conclusive for all conditions of 

 the decomposition of carbonic acid by plants, that under certain circumstances Ozone 

 may exist within the vegetable cells and the passages between them, and that it is pos- 

 sible that some of the oxygen of the decomposed carbonic acid may at times appear as 

 Ozone, still, it is difficult to see how it can exert any oxidizing influence upon the free 

 Nitrogen within the plant, under the peculiar circumstances in which it must come in 

 contact with it. 



In order to study more fully the circumstances, and to examine, in some detail, the 

 value of the oxidizing and reducing forces operating in the vegetable organism, in the 

 different conditions to which it is subjected during growth, a number of experiments 

 have been made upon plants, under a variety of conditions more or less analogous to 

 those of ordinary growth. As the results of these investigations are too extended in their 

 bearings for full consideration in the present Paper, and are, moreover, not yet sufficiently 

 complete for publication, we shall give here only such of them as bear upon the point 

 now in question. 



It is obvious that the formation of Nitric acid, by the mutual action of Ozone and 

 free Nitrogen within the plant, will be dependent upon the activity of the oxidizing 

 power of the Ozone, and on the intensity of the reducing power of other substances in 

 contact with the Nitrogen to be oxidized. 



