instructive to observe how he tries to decide whether the
nitrates, sulphates and ammonia, which are found in the sap of
plants, are introduced from without, or are formed in them
from their constituent elements; he concludes finally that the
former is the more probable opinion. That the greater part at
least of the carbon of plants comes from the atmosphere could
scarcely be a matter of doubt with those who knew the writings
of Ingen-Houss; but Senebier devotes special attention to this
question; he endeavours to take all the co-operating factors
into the calculation, and especially to prove once more that the
oxygen given off from the plant in light comes from the carbon
dioxide which has been absorbed, that the green parts only
and no others are able to effect this decomposition, and that
there is a sufficiency of carbon dioxide in nature to supply the
food of plants. But although he convinced himself that green
leaves decompose the carbon dioxide which surrounds them in
a gaseous form, he supposed that it is chiefly through the roots
that this substance finds its way with the ascending sap into
the leaves, and this view often gave occasion to further error in
later writers.
The tedious prolixity of Senebier's book was one reason why it never enjoyed the measure of appreciation and influence which it deserved; but it was also thrown into the shade by the appearance of a work of superior excellence, distinguished at once by the importance of its contents, by condensation of style, and by perspicuity of thought. This work was the 'Recherches chimiques sur la végétation' of Théodore de Saussure[1] (1804), which contained new observations and new
- ↑ Nicolas Theodore de Saussure was born at Geneva in 1767, and died there in 1845. He was the son of the famous explorer of the Alps, and assisted his father in his observations on Mont Blanc and the Col du Géant. In 1797 he wrote his treatise on carbonic acid in its relation to vegetation, a prelude to his 'Recherches chimiques'; the latter work received great attention from the scientific world, and he was made a corresponding member of the French Institute. He was a man of literary tastes, and took
