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 
