THE VEGETABLE KINGDOM. 417 



to M. Brongniart, the law of equilibrium is such at this 

 moment, that plants seem to pour into the atmosphere 

 as much ox3'gen as animals consume. 



Nothing is easier than to estimate the qiiantity of 

 oxygen which plants distil at every pore into the atmos- 

 phere. For this it is only necessary to put one under a 

 bell-glass filled with water; as soon as it is exposed to the 

 light, all its foliage becomes covered with bubbles of gas 

 which are disengaged from it, and rise without ceasing 

 to the top of the vase. If we now analyze the product 

 collected there, we find, from the brilliancy it gives to 

 bodies in a state of ignition, that it is oxygen and in pos- 

 session of all its attributes. 



But it is a remarkable fact that this salutary interven- 

 tion of plants is only manifested under the influence of 

 light. Were the star from which light emanates to be 

 extinguished, it would cease in a moment, and the globe, 

 plunged in obscurity, would soon be deprived of its green 

 tunic. Lavoisier was therefore right when he said : — 



" Organization, feeling, spontaneous movement and 

 life only exist on the surface of the earth, or in parts 

 exposed to light. One might say that the fable of the 

 torch of Prometheus expressed a philosophic truth which 

 had not escaped the ancients. Without light nature 

 would be without life; she would be dead and inani- 

 mate; a beneficent God, by imparting light, has shed 

 over the surface of the earth organization, sensation and 

 thought." 



But during the night the respiratory phenomena of 

 plants take the very opposite direction; then they act like 

 animals. They absorb the vital part of the air and exude 

 carbonic acid by all their pores, to such an extent that 

 if we sleep in a close chamber in which shrubs have been 



