46 THE FOOD OF PLANTS CHAP, v 



roots remaining in the water outside, and expose 

 the whole to the sun. 



After exposing all day, remove the plant, stopper 

 the bottle, lift it out, and test the air in it with a 

 lighted match. The match will now burn, showing 

 that the plant acting in sunlight has been able 

 to restore the air to its former state. 



We can now easily find out if exposure to sun- 

 light had anything to do with the action of the 

 plant. 



Repeat the last experiment, only keep the plant 

 in the dark instead of in the sunlight, and test with 

 the match. The air will remain unaltered and the 

 match will go out, showing that the plant cannot 

 restore the air without the assistance of light. 



"We have now found that the plant does 

 not obtain all its food from the soil through 

 the roots, but also obtains food from the air, 

 and that we find this food in the form of 

 charcoal when we heat the plant. We also 

 know that charcoal enters into the substance 

 of animals as well as vegetables. 



We have further discovered that air is 

 altered in some way by burning bodies, and the 

 breathing of animals, and is restored to its 

 former condition by the action of plants in 

 sunlight. 



