THE SOIJECES OE THE XITEO&EX OE YEaETATION, 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 Avhich 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 li\ing cells of any plant of -which it is not a natural 
product of growth I 
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 I ounce of the green plant w'as 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 v/ithin 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. xVs 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. 
