66 THE SPIRIT OF THE SOIL 



the food that they absorb. This central fact is 

 fundamentally important to a proper understanding 

 of the subject. Many perhaps do not realize the 

 magnitude of the work done by the plants in breaking 

 up Carbon dioxide. The chemist in the laboratory 

 can only achieve it by an intense expenditure of 

 energy. Thus it is a common elementary experi- 

 ment to show that some such energetic substance 

 as Phosphorus must be used to decompose the gas. 

 The Phosphorus is placed in the Carbon dioxide 

 and heated, and in these conditions is able to seize 

 the Oxygen from the Carbon dioxide, and leave the 

 Carbon behind in the form of black particles. 

 Another experiment on which a chemical lecturer 

 will insist is the burning of a wood match. Once 

 the temperature of the match is raised to a suffi- 

 ciently high point it burns, the Carbon in it uniting 

 with the Oxygen of the air, large quantities of energy 

 appearing during the process as heat and light. It 

 is reasonable and scientifically exact to believe that 

 a corresponding amount of energy would have to be 

 supplied for the converse process to take place 

 i.e., for the Carbon dioxide of the air to be recon- 

 verted into the wood of the match. Yet this is what 

 is being done day by day quietly by the plants, the 

 energy required for the purpose being derived from 

 the rays of the sun and absorbed by means of the 

 green chlorophyll in the leaves. 



The animal or the bacterium in taking in food is 

 absorbing materials which are able to give him the 

 vast quantities of energy he requires for his life. 

 From the point of view of energy there is no funda- 



