Place some seeds on a sponge under an air-tight glass. Will they grow?
What causes them to mould?
Seeds will not germinate without free access of air. They must have free
oxygen to breathe, as must every living thing. We know that an animal
breathes in oxygen, that the oxygen unites with particles of carbon within
the body and that the resulting carbonic acid gas is exhaled.[1] The same
process goes on in plants, but it was until recently entirely unknown,
because it was completely masked during the daytime by the process of
assimilation, which causes carbonic acid to be inhaled and decomposed, and
oxygen to be exhaled.[2] In the night time the plants are not assimilating
and the process of breathing is not covered up. It has, therefore, long
been known that carbonic acid gas is given off at night. The amount,
however, is so small that it could not injure the air of the room, as
is popularly supposed. Respiration takes place principally through the
stomata of the leaves.[3] We often see plants killed by the wayside dust,
and we all know that on this account it is very difficult to make a hedge
grow well by a dusty road. The dust chokes up the breathing pores of the
leaves, interfering with the action of the plant. It is suffocated.
The oxygen absorbed decomposes starch, or some other food product of the
plant, and carbonic acid gas and water are formed. It is a process of slow
combustion.[4] The energy set free is expended in growth, that is, in the
formation of new cells, and the increase in size of the old ones, and in
the various movements of the plant.
[Footnote 1: See page 13.]
[Footnote 2: This table illustrates the differences between the processes.