Far the greatest part of the plant produces the volatile matter,
consisting of Carbonic Acid, Water and Ammonia, three substan-
ces which can be farther divided into their elementary constituents:
Carbon, Hydrogen, Nitrogen and Oxygen.

These single substances, are the fundamental constituents of all
organic bodies; and plants must therefore be constantly supplied,
with them whilst the processes of life continue to take place in
them.

Animals live on both vegetable and animal food, and are conse-
quently referred to, and supported by the vegetable kingdom; they
could not exist before vegetation covered the lifeless mineral crust
of our globe. Plants, on the other hand, must necessarily assign
to themselves food of far more simple constitution. When they
first made their appearance, they did not find any thing else offered
to them for food, but what already existed as constituent parts of
the atmosphere, and earth.

In accordance with this, our daily experience teaches us, that
the wants of plants are supplied by both these media, viz: that the
forms in which the plants assimilate their Carbon, Hydrogen, Ni-
trogen and Oxygen, are those of Carbonic Acid, Water and Am-
monia, contained in, and furnished by, the air; and that, on the
other hand, the forms in which the plants assimilate the constituents
of their ashes, are those of Silicates, Phosphates, Sulphates, Chlor-
ides, alkaline, and earthy salts, as contained in, and furnished by,
the soil.

The latter position cannot be doubted; no other source exists for
the supply of mineral substances, but the earth. As to the former
however, that Carbonic Acid, Water and Ammonia, are the only
forms which supply the organic constituents of plants, it has been
often opposed, and is still opposed by many at the present day.—
it is a fact that the productiveness of soils is somewhat influenced
by the quantity of Humus contained in them, and accordingly the
principal objection made against our theory is this, viz: that Hu-
mus is assimilated by the plants in form of Humus, and thus par-
ticipates directly in the formation of the organic parts of plants, or,
in other words, plants live on organized bodies.

We have no reason to adopt a theory which is not only strongly
opposed to natural philosophy, but which is also positively contra-
dicted by facts. We see plants growing and becoming developed
in a soil which neither contains Humus, nor any substance of or-
ganic origin. This occurs in many parts of our globe, and is also
confirmed by direct experiments, upon soils which before being
used, had been calcined, and thus deprived of all organic matter.

On the other side, the plant is not able to appropriate to itself
and to assimilate its constituents, in their isolated, elementary form;
for a plant which is planted in pure chat coal, and surrounded by an
atmosphere of Hydrogen, Nitrogen and Oxygen, will soon die for
want of suitable nourishment.

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