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REPORT ON BOTANY, MDCCCXLl : 
GEOWTH— NUTRITION. 
Cpiemical researches can only be taken into consideration 
here, in as far as they have reference to the plant as an 
individual. They belong to a division of chemistry, called 
organic, which only contemplates substances produced by a 
vital process. 
An important work has lately been published, in relation 
to the nutrition of plants : Organic Chemistry^ in its Ap- 
plication to Agriculture and Physiology, by Justus Liebig. 
Brunswick, 1840. The contents of this work are well known 
to all who are occupied with subjects of this kind, and it will 
not be necessary to give extracts from it. I shall, therefore, 
only take the liberty of making a few remarks. It proves, in 
a very convincing manner, that the substances which are taken 
up from the humus, by water, are not sufficient to yield the 
carbon which is found in plants. It would, on the other hand, 
have been desirable, if it had been proved equally satisfac- 
torily, that the atmospheric air, which surrounds the plants, 
both in the quantity of carbonic acid contained in it, and 
decomposed by the plant, was sufficient to afford the plant 
the carbon which it requires for its sustenance. The author’s 
remarks on this point are very arbitrary. He calculates the 
weight of the whole atmosphere, the thousandth part of the 
weight of which, according to the experiments of Saussure, is 
carbonic acid ; and thus gives a number of pounds for the car- 
bonic acid contents, which far exceeds the quantity of carbon 
in plants. He further assumes, that the surface of the leaves 
of plants, is twice as great as that of the surface of the soil 
upon which they grow ; and that in each second of time, 
during eight hours daily, 1-lOOOth part of its weight of car- 
bonic acid is extracted from the atmosphere ; so that the leaves, 
in 200 days, take up 1000 pounds of carbon. The last asser- 
tion is entirely hypothetical. The first calculation is founded 
upon the circumstance, that carbonic acid is equally diffused 
through the whole atmosphere ; a fact, however, which is by no 
means perfectly established. Experiments in Ward’s apparatus 
488 
