Plants and the Atmosphere 



heart, deprived of the sunlight, may become 

 tender and white. Celery and cardoons, 

 the flavour of which would be unendurable 

 without this treatment of darkness, are 

 partly buried. If we cover the grass with 

 a tile, or hide a plant under a flower-pot, 

 after a few days without light we shall And 

 their leaves sickly and yellow. 



On the contrary, when the plant receives 

 the rays of the sun directly, the carbonic 

 acid gas is decomposed at once ; the carbon 

 and the air separate, and each resumes its 

 original qualities. When deprived of its 

 carbon the air becomes that which it was 

 before entering into combination with it : 

 it is pure air, able to support fire and life. 

 In this state it is restored to the atmosphere 

 by the stomata, and serves again for com- 

 bustion and respiration. As a fatal gas it 

 entered the leaf, as a life-giving gas it leaves 

 it. It will return some day with a fresh 

 load of carbon, will deposit it in the plant 

 and then, purified at once, will resume its 

 aerial journey. The swarm comes and goes 

 from the hive to the fields and from the fields 

 to the hive, light and eager for booty ; or 

 else loaded with honey and returning to the 

 combs with burdened flight. Thus the air 



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