142 THE GREENWOOD TREE. 



the air, from whence it came, as carbonic acid. Dust to 

 dust, ashes to ashes ; but air to air, too, is the rule of 

 nature. 



It may sound startling to Other People, I mean but 

 the simple truth remains, that trees and plants grow out 

 of the atmosphere, not out of the ground. They are, in 

 fact, solidified air ; or to be more strictly correct, solidi- 

 fied gas carbonic acid. 



Take an ordinary soda-water syphon, with or without 

 a wine-glassful of brandy, and empty it till only a few 

 drops remain in the bottom. Then the bottle is full of 

 gas ; and that gas, which will rush out with a spurt when 

 you press the knob, is the stuff that plants eat the raw 

 material of life, both animal and vegetable. The tree 

 grows and lives by taking in the carbonic acid from the 

 air, and solidifying its carbon ; the animal grows and 

 lives by taking the solidified carbon from the plant, and 

 converting it once more into carbonic acid. That, in its 

 ideally simple form, is the Iliad in a nutshell, the core 

 and kernel of biology. The whole cycle of life is one 

 eternal see-saw. First the plant collects its carbon com- 

 pounds from the air in the oxidized state ; it deoxidizes 

 and rebuilds them : and then the animal proceeds to burn 

 them up by slow combustion within his own body, and to 

 turn them loose upon the air, once more oxidized. After 

 which the plant starts again on the same round as before, 

 and the animal also recommences da capo. And so on 

 ad infinitum. 



But the point which I want particularly to emphasize 

 here is just this : that trees and plants don't grow out of 

 the ground at all, as most people do vainly talk, but 



