526 at Royal Society :— 
sun’s rays (liberating oxygen) on the other. Both actions may: 
go on simultaneously according to the depth of the cell; and the 
once outer cells may gradually pass from the state in which the. 
sunlight is the greater reducing agent to that in which the carbon- 
matter becomes the greater. 
4. The great reducing power operating in those parts of the plant. 
where ozone is most likely, if at all, to be evolved, seems unfavour-: 
able to the oxidation of nitrogen; that is under circumstances in 
which carbon-matter is not oxidized, but on the contrary, carbonic 
acid reduced. And where beyond the influence of the direct rays of. 
the sun, the cells seem to supply an abundance of more easily oxi- 
dized carbon-matter, available for oxidation should free oxygen or 
ozone be present. On the assumption that nitrates are available as 
a direct source of nitrogen to plants, if it were admitted that nitrogen 
is oxidated within the plant, it must be supposed (as in the case of 
carbon) that there are conditions under which the oxygen compound 
of nitrogen may be reduced within the organism, and that there are 
others in which the reverse action, namely, the oxidation of nitrogen, 
can take place. 
5. So great is the reducing power of certain carbon-compounds of 
vegetable matter, that when the growing process has ceased, and all 
the free oxygen in the cells has been consumed, water is for a time 
decomposed, carbonic acid formed, and hydrogen evolved. 
_ The suggestion arises, whether ozone may not be formed under 
the influence of the powerful reducing action of the carbon-com- 
pounds of the cell on the oxygen eliminated from carbonic acid by 
sunlight, rather than under the direct action of the sunlight itself 
—in a manner analogous to that in which it is ordinarily obtained 
under the influence of the active reducing agency of phosphorus? 
But, even if it were so, it may be questioned whether the ozone 
would not be at once destroyed when in contact with the carbon- 
compounds present. It is more probable, however, that the ozone 
said to be observed in the vicinity of vegetation, is due to the action 
of the oxygen of the air upon minute quantities of volatile carbo- 
hydrogens emitted by plants. 
Supposing ozone to be present, it might, however, be supposed to 
act in a more indirect manner as a source of combined and assimilable 
nitrogen in the Authors’ experiments, namely,—by oxidating the 
nitrogen dissolved in the condensed water of the apparatus—by 
forming nitrates in contact with the moist, porous, and alkaline 
soil—or by oxidating the free nitrogen in the cells of the older 
roots, or that evolved in their decomposition. 
Experiments were accordingly made to ascertain the influence of 
ozone upon organic matter, and on certain porous and alkaline 
bodies, under various circumstances. <A current of ozonous air was 
passed over the substances for some time daily, for several months, 
including the whole of the warm weather of the summer; but in 
only one case out of eleven was any trace of nitric acid detected, 
namely, that of garden soil; and this was proved to contain nitrates 
before being submitted to the action of ozone. | 
