46 FIELD, FOREST AND FARM 



tain 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 atmos- 

 pheric round. A swarm of bees goes and comes, 

 f Bom 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 salu- 

 brity 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 re- 

 turns to the atmosphere. From this carbon com- 

 bined 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." 



