Southern planter : devoted to agriculture, horticulture, and the ...

416 THE SOUTHERN PLANTER,
it passes off by exhalation, or evaporation
of the leaves. The amount of water daily
evaporated by large-leaved plants, like the
cabbage, pumpkin, grape, and sunflower,
especially when under the influence of a
warm, dry atmosphere, aided by the direct
rays of the sun, is much greater than
some persons may be aware of. Hales
made an experiment with a sunflower three
feet high, inclosed in a vessel, wiiich he
kept for fifteen days ;
and inferred from it,
that the weight of the fluid daily exhaled
by the plant was twenty ounces. Mr.
Everett in his address at Buffalo, stated
there had grown seven millions of counted
leaves on a single tree." If Hale's three
feet sunflower, with its dozen leaves, exhaled
twenty ounces of M'ater per diem,
how many pounds will daily be evaporated
by the " seven millions of leaves on a
single tree?" Can any of our juvenile
readers figure it out for us ?
From the foregoing it will be seen that
one of the important functions of the
leaves of a plant, is to carry off the surplus
water—to boil down, as it was, the
crude, dilute sap, holding in solution the
various salts or mineral ingredients that
make up " part and parcel " of all plants
and thus, by a greater concentration of the
mineral ingredients held in solution by the
sap, they are more fully prepared to enter
into the various chemical combinations
with carbon, and the other organic constituents
whicli make up the entire and per-
fect plant in all its varied parts.
But the leaves of plants, besides their
exhaling power, have another important
function to perform in the phenomena of
vegetable life. It is through the agency
of the leaves that most of the woody and
other carbonaceous structures of plants are
derived. Carbon in one form or another,
is the leading combustible substance in all
fuel generally used— in wood, coal, charcoal,
oil, rezin, pitch, &c. While burning,
the carbon unites with the oxygen of the
atmosphere, resulting in carbonic acid
and every cord of wood burned, restores
to the atmosphere just carbon enough to
grow another cord. By passing into the
air, the carbon is not lost; there is no such
word as lost in the whole vocabulary of
nature. Carbonic acid oras, thouo^h much
heavier than common air, is by the great
law of gaseous diffusion, equally difl:used
through the atmosphere, composing abou^
l-2500th part of it.
When sugar or salt is mixed with water,
it dissolves and becomes invisible—when
carbon is burned, it is in fact dissolved in
oxygen gas, and the carbon becomes invisible.
By evaporating the water holding
the sugar or salt in solution, we again obtain
the sugar and salt in precisely the state
they were in before solution. But we
cannot, by any known chemical or other
process, obtain carbon from carbonic acid
in the form of wood, oil or starch. To do
this requires the more efficient agency of
vegetable chemistry.
In the economy of nature, it has been
so arranged that the healthy leaves of
plants in sun light, can and do inhale from
the air with which they are surrounded,
the carbonic acid that seems so sparsely
mingled with it—to do this the leaves
have been endowed with very nice discriminating
powers ; and further, they have
the power of decomposing the carbonic
acid, that is, separating the oxygen from
the carbon, which they retain, and returning
to the atmosphere the oxygen in a
pure form.
When a fresh leaf is examined by a
microscope, its whole surface is seen to be
covered with minute pores on each side of
the leaf; each of these j)ores is a species
of mouth, intended to receive food or to
give off something that the plant no longer
requires. A high magnifying power discovers
more than 100,000 openings in a
square inch upon the surface of some
leaves ; others have not more than 600
700. Analogous to this is the skin of animals,
which is perforated with a thousand
pores in the length of an inch, through
which the insensible perspiration passes.
It is no more marvellous that the leaf of
a plant can take in the carbonic acid of
the air, separate it, and retain the carbon
and reject the oxygen,* than it is that a
grown up boy can take into his mouth a
ripe peach and separate the stone and pulp,
and swallow the pulp and spit out the
stone. From whence did the boy derive
his ability to pass the pulp of the peach
through the gullet into the stomach ? From
the same Being: that endowed the leaf
* In 2'2 lbs. of carbonic acid, there is 6 lbs. of
carbon and 18 lbs. of oxvgeii.