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It is a common, not to say a vulgar error, to believe that trees and plants grow out of the ground. And of course, having thus begun by calling it bad names, I will not for a moment insult the intelligence of my readers by supposing them to share so foolish a delusion. I beg to state from the outset that I write this article entirely for the benefit of Other People. You and I, O proverbially Candid and Intelligent One, it need hardly be said, are better informed. But Other People fall into such ridiculous blunders that it is just as well to put them on their guard beforehand against the insidious advance of false opinions. I have known otherwise good and estimable men, indeed, who for lack of sound early teaching on this point went to their graves with a confirmed belief in the terrestrial origin of all earthly vegetation. They were probably victims of what the Church in its succinct way describes and denounces as Invincible Ignorance.

Now, the reason why these deluded creatures supposed trees to grow out of the ground, instead of out of the air, is probably only because they saw their roots there.

Of course, when people see a wallflower rooted in the clefts of some old church tower, they don’t jump at once to the inane conclusion that it is made of rock–that it derives its nourishment direct from the solid limestone; nor when they observe a barnacle hanging by its sucker to a ship’s hull, do they imagine it to draw up its food incontinently from the copper bottom. But when they see that familiar pride of our country, a British oak, with its great underground buttresses spreading abroad through the soil in every direction, they infer at once that the buttresses are there, not–as is really the case–to support it and uphold it, but to drink in nutriment from the earth beneath, which is just about as capable of producing oak-wood as the copper plate on the ship’s hull is capable of producing the flesh of a barnacle. Sundry familiar facts about manuring and watering, to which I will return later on, give a certain colour of reasonableness, it is true, to this mistaken inference. But how mistaken it really is for all that, a single and very familiar little experiment will easily show one.

Cut down that British oak with your Gladstonian axe; lop him of his branches; divide him into logs; pile him up into a pyramid; put a match to his base; in short, make a bonfire of him; and what becomes of robust majesty? He is reduced to ashes, you say. Ah, yes, but what proportion of him? Conduct your experiment carefully on a small scale; dry your wood well, and weigh it before burning; weigh your ash afterwards, and what will you find? Why, that the solid matter which remains after the burning 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.