152 PHYSIOLOGICAL BOTANY. 



entire plant world, and the proportion of solid carbon which 

 enters into that amount, we should doubtless find that the grand 

 total of the demand equals this grand total supply. 



491. -And further: not only are the necessities of the plant 

 met by this wonderful circulation, but the necessities of animal 

 existence also. Carbonic acid is poisonous ; and should it be left 

 to accumulate unchecked, it would gradually corrupt the air, and 

 within a few centuries extinguish all animal life. Thus are the 

 two kingdoms of the organic world mutually, through the inor- 

 ganic, dependent upon each other. The plant furnishes the 

 oxygen which the animal consumes, the animal the carbonic acid 

 which the plant consumes, while each would perish in an atmos- 

 phere of its own production. " Great and marvellous are thy 

 works, O Lord of Hosts ! in wisdom hast thou made them all." 



Review. 479. What is transpiration ? It occurs where and when ? 480. Why is absorp- 

 tion dependent upon it? What only does it expel? 481. How mnch water did a Sun- 

 flower transpire in a day? A Cabbage? Effect of a forest on the Atmosphere ? 483. Im- 

 port of Aeration. Vastness of the Apparatus. 484. Six fact* in Respiration. 485. The 

 two opposite phases of respiration. 486. When does the former phase become visible? 

 When the latter ? Blanched plants. 487. Saussure's Experiments. Why no oxygen with 

 boiled water? 489. The results of transpiration and respiration. 490. What proportion, 

 of CO, in the Air? Whence is it? How much added yearly? Does it accumulate? 

 Why not ? 491. How might the air become poison ? The mutual dependence of Plants 

 and Animal?. 



