lit 1 MK. J. B. LAWKS, DE. GILBERT, AND DE. PI '.II OH 



to plants as ammonia; and hence, if we were to admit thai Nitrogen can be 

 into nitric acid in the plant, we inn -i Buppose, a in the ca le of carbon, that tin i. 

 conditions under which the oxygen compound of Nitrogen is reduced within the 

 organism, and that then' are others in which the reverse action, namely, the oxidation 

 of Nitrogen, c;m take place. In relation to this question, it may be mentioned that 

 several specimens of green Wheat and Grass which had been liberallj manured with 

 nitrates were examined for nitric acid, bul no trace of it was found in them. 



7. To the foregoing six conclusions, another may be here added relating to this sub- 

 ject, though deduced from the results of experiments on the decomposition of organic 

 matter, which will be referred to more fully presently (p. 509 et ■"/■)■ So great is the 

 reducing power of certain carbon-compounds of vegetable substances, that when the 

 vital (growing) process has ceased, and all the free oxygen in the cell- has been con- 

 sumed, in the formation of carbonic acid, water is decomposed, and hydrogen is evolved. 

 This process does not, however, continue long, showing that the cell provides a certain 

 amount of matter more easily oxidized than the remainder, or that the entire cell- 

 matter, after becoming slightly oxidized, loses its energetic reducing-power. The former 

 alternative is the more probable one. 



The foregoing considerations with regard to the intensity of the reducing action of 

 certain of the carbon-compounds in plants suggest the idea of a possible source of Ozone, 

 very analogous to that by which it is ordinarily obtained by means of phosphorus. As 

 is well known, the process consists in allowing oxygen to come into incomplete or only 

 instantaneous contact with phosphorus. This substance having an intense avidity for 

 oxygen, a part of the latter unites with it to form an oxygen-compound of phosphorus, 

 when, if the contact be not too long, another part passes off in the state of Ozone. 

 Certain carbon-compounds of the vegetable cell have also a great affinity for oxygen in 

 the dark (p. 488) ; and the oscillations of the affinities, due to the degree of light (pages 

 489-492), and to the depth of the cell (p. 493), would afford conditions of molecular 

 action somewhat similar to those under which Ozone is produced in the presence of phos- 

 phorus. According to this analogy the Ozone would be due to the action of the carbon- 

 compounds of the cell on the common oxygen eliminated from carbonic acid by sun- 

 light, and not to the direct action of the sunlight itself. The Ozone thus formed, if not 

 instantly evolved from the plant, would be destroyed by the easily oxidizable carbon- 

 compounds present. It is more probable, however, that the Ozone, stated by De Lica 

 and others to be observable in the vicinity of vegetation, is due to the intense action of 

 the oxygen of the air upon the minute quantities of volatile hydrocarbons emitted 

 by the plants, and to which they owe their peculiar odours, than to any action going 

 on within the cells. The rapidity of the oxidation in the air of the hydrocarbons, 

 and the volatile principles of plants generally, goes to favour the view here suggested ; 

 so also does the fact, that Ozone has been observed most readily in the vicinity of such 

 plants as are known to emit freely essential oils — as, for instance, those of the Labiate 

 family. 



