THE FOLIAGE— AND ITS FUNCTIONS. 
57 
in the saccharine juice of its cane, nor yet in its nearer relative, the fluid sugar of 
the grape. 
"Observing these cautions, we proceed thus : — the tree, it is said, could not have 
obtained this charcoal from the ground, because the ground around the tree becomes 
richer in carbon during its growth ; the oak, therefore, has derived its carbon from 
the air. While, therefore, the sun shines on the leaves, they have the power of 
absorbing the charcoal from the carbonic acid of the air ; and that plants have this 
power is a well known fact, attested by experiments, which have been tried over and 
over again." 
There it is, at this very point, that we solicit the earnest attention of our readers. 
Boussingault, we are told, put a branch of a vine into a glass tube while the plant 
was growing, and through this tube was sent a current of air containing a certain 
per centage of carbonic acid. This gas is easily detected by the white sediment 
which it produces in lime water. When the gas was passed through the tube, while 
the sun shone brightly on the branch of the vine inclosed, not a particle issued 
therefrom ; or in any degree affected the lime water contained in the vessel with 
which the tube was connected. A number of experiments, similar in character, have 
been performed in Britain, and on the Continent, all tending to prove that carbon 
is absorbed, during sunshine, from carbonic acid, by the leaves, wherein the 
carbon, or elemental base of woody matter is retained, while the oxygen is liberated, 
and passes in a free state through the air and water which had held the carbonic 
acid in solution. But Nature does not act in this way; carbonic acid does exist in the 
atmosphere ; but trees and their branches are free and open to the air, the sun, the 
dew, and other meteorological agents ; they are not confined in tubes, under bell- 
glasses ; some containing water, medicated fluid, or in contact with gases, either in 
quality or quantity disproportionate to their natural habits, and always exposed to 
sunbeams refracted through one or more glasses. Experiments so conducted, appear 
to be inconclusive ; for, is it probable that natural results can be attainable by means 
or agents unnaturally applied ? 
That carbonic and ammoniacal gases do exist in the air may be safely asserted ; 
for, how else could the exhalations from decomposing animal and vegetable matters 
be disposed of ? By parity of reasoning, we may presume that plants act by 
attraction as purifiers of the air. But as the ground performs so important an office 
in all the processes of nutritious supply, and, as in the absence of terrene moisture, 
plants must sicken and perish, we are constrained by the paramount evidence of 
facts, to refer to the earth as the grand medium of supply, and still to regard with 
jealousy any theory based upon ambiguous experiments. 
There does not exist a truly practical cultivator of the garden or field who is not 
certain that if his plants are dry at root they must either droop or perish in the 
glazed houses ; this truth is above all things manifested, and by the simple fact— 
though others are not wanting — that, however you may flow the ground, and in 
addition, so saturate the air with steam, that the glass and rafters shall flood with 
vol. xiv. — NO. CLIX. I 
