166 PLANT LIFE 



state of the water; in the latter, it is used 

 to construct complex out of relatively simple 

 chemical substances. And in this process 

 the energy, instead of becoming dissipated 

 over an infinite field, is concentrated within 

 narrow limits. It is again locked up as 

 potential energy in the construction of chemi- 

 cal molecules, and it can be reconverted into 

 the kinetic form when the molecular groupings 

 once more break down. 



We have already seen that the various 

 organic substances on which the fungi and 

 other colourless parasites and saprophytes 

 subsist are all traceable more or less directly 

 to the synthetic processes of the green plants. 

 The latter are empowered to build up this 

 organic material by utilising the energy of 

 the sunlight for the work. Thus we are 

 justified in saying that the products of 

 photosynthesis practically represent the total 

 means available for supplying the energy 

 required to drive the machinery of the rest 

 of the life of the world. In other words, 

 the potential energy of the organic food is 

 resolved into kinetic energy in the body of 

 an organism, and it is solely by virtue of 

 this kinetic energy that an organisn can live 

 and move and have its being. 



Now the essential chemical process which 

 is carried on when the energy of the sunlight 

 drives the photosynthetic machinery of the 

 green plants results in reduction or deoxida- 

 tion. The carbohydrate food the tangible 



