466 
]ME. J. B. LAWES, DR. GILBERT, AND DR. PUGH ON 
in sunlight was in many cases ozonous. He aspirated a large quantity of air, in the 
neighbourhood of vegetation, through carded cotton, and then through sulphuric acid, 
to wash it. The washed air then passed over potassium, and through a dilute solution 
of pure potash, when nitrate of potash was formed. When, on the other hand, air in 
the midst of habitations was operated upon in a similar way, the formation of nitric 
acid was not observed. M. de Luca supposes the air surrounding vegetation, in sun- 
light, to be ozonous ; that by its means the Nitrogen of the air may be converted into 
nitric acid ; and that thus the Nitrogen of the air may be rendered available for assimi- 
lation by plants, under the influence of vegetation itself. 
G. — The Expeeiments op M. Haeting*. 
In 1855, M. Haeting published some criticisms, and the results of some experiments, 
on the question of the assimilation of Nitrogen by plants. He considered that the 
Nitrogen of the air might contribute indirectly to vegetation. He attributed a forma- 
tion of ammonia from the decomposing debris of seeds, &c., and the free Nitrogen of 
the air, in the case of M. Ville’s experiments ; and also supposed that nitric acid 
might be formed by the oxidation of the atmospheric Nitrogen. The increase of Nitro- 
gen in M. Ville’s plants, and of ammonia in the water of the enclosing apparatus, was 
taken as proof of such formation of ammonia. 
M. Haetixg made two sets of experiments, in one of which the plants grew in a limited 
volume of air, and in the other in a current of air washed free from ammonia — both 
arranged with a view to avoid the formation of ammonia. He employed enclosing-appa- 
ratus somewhat on the plan of M. Boussingault and M. Ville ; but he used glass vases, 
instead of porous pots, for his plants. He grew Beans, Buckwheat, and Oats. After 
the seeds had germinated, and the plants had protruded a little above the surface of the 
artificial soil, he covered the latter with a mixture of wax and oil, to shut off the access 
of air. He further enclosed the stems of the plants in caoutchouc tubes ; and inserted 
other caoutchouc tubes through the waxy coating, for the supply of water. Some of the 
plants were very vivacious at first ; and in the case of the Beans, two began to flower ; 
but then the leaves turned yellow, and the experiment was stopped. His apparatus 
consisted of tinned-iron pans, varnished, and surmounted by glass shades of 18 litres 
capacity. There was an aperture for the admission of carbonic acid, another for that of 
water, and so on. 
The result was that the produced plants yielded no more dry matter than was con- 
tained in the seeds. M. Haeting considered, therefore, that the determination of the 
Nitrogen was superfluous. The growth evidently stopped when the supplies of the seeds 
were exhausted. M. Haeting’s general conclusions on the subject were as follow: — 
1. Plants absorb salts of ammonia, and nitrates, by their roots. 
2. The Nitrogen of the air contributes to the formation of ammonia, and nitrates, in 
the soil. 
3. It is not proved that Nitrogen serves directly for the nutrition of plants. 
* Compt. Rend. xli. 1855. 
