rning is a mere infinitesimal fraction of the total
weight: the greater part has gone off into the air, from whence it
came, as carbonic acid. Dust to dust, ashes to ashes; but air to air,
too, is the rule of nature.

It may sound startling--to Other People, I mean--but the simple truth
remains, that trees and plants grow out of the atmosphere, not out of
the ground. They are, in fact, solidified air; or to be more strictly
correct, solidified gas--carbonic acid.

Take an ordinary soda-water syphon, with or without a wine-glassful of
brandy, and empty it till only a few drops remain in the bottom. Then
the bottle is full of gas; and that gas, which will rush out with a
spurt when you press the knob, is the stuff that plants eat--the raw
material of life, both animal and vegetable. The tree grows and lives
by taking in the carbonic acid from the air, and solidifying its
carbon; the animal grows and lives by taking the solidified carbon from
the plant, and converting it once more into carbonic acid. That, in its
ideally simple form, is the Iliad in a nutshell, the core and kernel of
biology. The whole cycle of life is one eternal see-saw. First the
plant collects its carbon compounds from the air in the oxidized state;
it deoxidizes and rebuilds them: and then the animal proceeds to burn
them up by slow combustion within his own body, and to turn them loose
upon the air, once more oxidized. After which the plant starts again on
the same round as before, and the animal also recommences _da capo_.
And so on _ad infinitum_.

But the point which I want particularly to emphasize here is just this:
that trees and plants don't grow out of the ground at all, as most
people do vainly talk, but directly out of the air; and that when they
die or get consumed, they return once more to the atmosphere from which
they were taken. Trees undeniably eat carbon.

Of course, therefore, all the ordinary unscientific conceptions of how
plants feed are absolutely erroneous. Vegetable physiology, indeed, got
beyond these conceptions a good hundred years ago. But it usually takes
a hundred years for the world at large to make up its leeway. Trees
don't suck up their nutriment by the roots, they don't derive their
food from the soil, they don't need to be fed, like babies through a
tube, with terrestrial solids. The solitary instance of an orchid hung
up by a string in a conservatory on a piece of bark, ought to be
sufficient at once to dispel