“When, on the other hand, the plant receives the sun’s rays without hindrance, the carbonic acid gas is decomposed in no time, the carbon and the air separate, and each resumes its original properties. Freed of its carbon, the air becomes what it was before this admixture: it becomes pure air, fit to maintain both fire and life. In this state it is restored to the atmosphere by the stomata to be used again in combustion and respiration. It entered the plant as a fatal gas, it leaves it as a vivifying gas. It will return some day with a new charge of carbon, which it will deposit in the plant, and then, restored to purity once more, it will recommence its atmospheric round. A swarm of bees goes and comes, from the hive to the fields and from the fields to the hives, on one trip lightened and eager for booty and on the other heavily laden with honey and returning to the comb on wearied wing. In the same way air on coming to the leaves is charged with carbon from an animal’s body, a burning fire-brand, or decaying matter; it gives it to the plant and departs for a fresh supply. “It is thus that the atmosphere preserves its salubrity despite the immense torrents of carbonic acid that are cast into it. The plant lives on deadly gas. Under the action of the sun’s light it decomposes the gas into carbon, which it keeps for building up its own substance, and breathable air, which it returns to the atmosphere. From this carbon combined with other substances come wood, sugar, starch, flour, gum, resin, oil, in fact every kind of vegetable product. Animal and plant are of mutual assistance, the animal producing carbonic acid gas, which nourishes the plant, and the plant changing this deadly gas into air fit to breathe and into food. Thus our dependence on plants is twofold: they purify the atmosphere and they give us food.” CHAPTER IX LIME