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.

ASSIMILATION PROPER.  RESPIRATION.

Takes place only in cells Takes place in all active cells. containing chlorophyll.

Requires light.  Can proceed in darkness.

Carbonic acid absorbed,            Oxygen absorbed, carbonic
oxygen set free.                     acid set free.

Carbohydrates formed.  Carbohydrates consumed.

Energy of motion becomes           Energy of position becomes
energy of position.                energy of motion.

The plant gains in dry The plant loses dry weight. weight.

Physiological Botany, page 356.]

[Transcriber’s Note:  Two footnote marks [3] and [4] above in original text, but no footnote text was found in the book]

This process of growth can take place only when living protoplasm is present in the cells of the plant.  The substance we call protoplasm is an albuminoid, like the white of an egg, and it forms the flesh of both plants and animals.  A living plant can assimilate its own protoplasm, an animal must take it ready-made from plants.  But a plant can assimilate its food and grow only under the mysterious influence we call life.  Life alone brings forth life, and we are as far as ever from understanding its nature.  Around our little island of knowledge, built up through the centuries by the labor of countless workers, stretches the infinite ocean of the unknown.

Gray’s First Lessons.  Sect.  VII, XVI, sec. 2, sec. 4, sec. 5, sec. 6, 476-480.

How Plants Grow.  Chap.  I, 119-153, Chap.  III, 261-280.