THE SOURCES OF THE MTEOOEN OF VEOETATION, ETC. 
465 
considered, appropriated carbonate of ammonia from the atmosphere by their leaves. 
Graminaceous crops, on the other hand, he supposed, only took it up in solution by 
their spongioles. He further supposed that the free Nitrogen of the air vras not appro- 
priated by the leaves of plants, but that Nitrogen dissolved in water, and so taken up, 
by their roots, could be assimilated. He concluded that, in the case of M. Boussiisr- 
gatjlt’s plants growm in hmited air, there would be but little passage of solution of 
Nitrogen by their roots, and evaporation of water from their leaves, and that, hence, the 
necessary conditions did not exist for the assimilation of free Nitrogen. M. Ville’s 
rapid current of air would, on the other hand, cause a considerable amount of solution 
of Nitrogen to be clrawTi into the plants, 
E. — The Expeediexts of MM, Cloez axd Geatiolet. 
In 1850, MM. Cloez and Geatiolet published the results of some experiments made 
with Water-plants. They found that, carbonic acid and air being both present, the 
plants gave off oxygen slowly, or very rapidly, according to the condition of the sunlight 
and the temperature. In water deprived of common air, but containing carbonic acid, 
the evolution of oxygen rapidly declined. Nitrogen was given off, and the plant contained 
less Nitrogen than a similar plant in water not deprived of its air. The evolution of 
Nitrogen diminished as the experiment proceeded. They considered that, in the vege- 
tation of Water-plants, Nitrogen is given off from their nitrogenous constituents and 
that there must be restoration either from free or combined Nitrogen. And as their 
experiments showed that ammonia-salts were injurious to the plants, they concluded 
that they take up free Nitrogen dissolved in water. 
In 1855* M. Cloez published the results of some experimental inquiries on nitrifica- 
tion, with a Hew to the question of the source of the Nitrogen of plants. He made 
twenty experiments, passing washed air through as many different combinations of 
porous, earthy, and alkaline matters. The experiments continued from September 1854 
to April 1855, when, in some cases, efflorescence was observed. He found nitrates to 
be formed in notable quantity in calcined brick, or pumice, impregnated with alkaline 
or earthy carbonates ; also, in uncalcined brick similarly impregnated. In chalk, marl, 
a mixture of kaolin and precipitated carbonate of hme, &c., only traces of nitrate were 
formed. 
M. Cloez concluded that nitrates would be formed when a current of air was passed 
over porous bodies, alkalies being present. He considered, therefore, that the porosity 
of the pots and brick fragments, the alkalinity of the ashes, the moisture, and the cur- 
rent of air, in M. Ville’s experiments with plants, prorided the conditions for the forma- 
tion of nitric acid. He asks, can such formation take place in limited air 1 
F. — The Expeeimexts of M. he LucAf. 
M. HE Luca found that, on passing moist ozonous air over potash and potassium, 
nitrate of potash was formed. He further found that the oxygen given off by plants 
* Compt. Eend. xli. f Ibid. 1856. 
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