COMPONENTS OF PLANTS

From the standpoint of their ability to synthetize synergic foods (see page
2) from inorganic raw materials, plants may be divided into two types;
namely, the _autotrophic_, or self-nourishing, plants, and the
_heterotrophic_ plants.

Strictly speaking, only those plants whose every cell contains chlorophyll
are entirely self-nourishing; and some parts, or organs, of almost any
autotrophic plant are dependent upon the active green cells of other parts
of the plant for their synergic food. Furthermore, if the term is used in a
very wide sense, green plants are more than self-nourishing, they really
nourish all living things. But the general significance of the term
"autotrophic plants" is apparent.

"Heterotrophic plants" must, of necessity, get food, either directly or
indirectly, from some other plant which can synthetize synergic foods or,
in a few cases, from animal organic matter. If they do this by feeding upon
the organic compounds of other living organisms, they are known as
"parasites"; while if they secure their organic food from the tissues or
debris of dead organisms, they are called "saprophytes." The heterotrophic
plants are chiefly the bacteria and fungi; although a few seed-plants are
devoid of chlorophyll or have nutritive habits similar to those of the
non-green plants, and a few species are semi-parasitic or semi-saprophytic.

It is obvious that the metabolic processes of the autotrophic plants are
very different from those of the heterotrophic type of plants. These
differences constitute a most interesting field of study for plant
physiologists. But the nature of the chemical compounds themselves and of
the chemical changes involved in their transformations is not radically
different in the two types of plants, the essential difference being in the
preponderance of one kind of activities, or chemical reactions, over
another in bringing about the metabolic processes which are characteristic
of each particular species. Hence, it does not seem necessary, or
desirable, in this study of the chemistry of plant growth, to present as
detailed a consideration of the differences in metabolic activity of the
different types of plants as complete accuracy of statement in all cases
might demand. We will, instead, discuss the organic chemical components of
plant tissues and the reactions which they undergo, using the more common
type of autotrophic plants as the illustrative material in m