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from each other the long cells, which, applied end to end, and
more or less filled with green matter, occupy all Its tubular
capacity.”
“ In order to remove entirely the green matter, it was
necessary to open the cells which retained or lield it, by
means of dissolvents. I contrived to effect this by squeezing
slightly together moistened Conferva, drying the mass,
afterwards submitting it to the action of lime, then alcohol,
ammonia, solutions of soda and potass diluted, removed
the azotized substances and green matter in solution.
Chlorine effaced the last traces by eliminating also a
brown substance ; hydrochloric acid, water, ether, and
alcohol perfected the purification by removing carbonate of
lime and fatty substances. The purified membranes of
Conferva rivularis and Oscillatoria presented then the composition
of the other vegetable tissues.”
The nature of the contents of the cells of the Conferva
is, it would appear by the preceding remarks, more complicated
than one would be led to suppose from a consideration of
the structure of the cells themselves. Starch is found in
them in considerable quantity, azotized substances, a fatty
matter, a colouring substance, and an odoriferous principle,
as well as salts. The Chara, M. Peyen remarks, contains
granules of starch, green azotized bodies, soluble azotized
substances, a fatty matter, a colouring substance,^ an
odoriferous principle, recalling the marshy odour of many
Cotferva, chloride of potassium, carbonate of lime adherent
to the exterior of the membrane, and sihca.
Nitrogen, as Is now well known, is the aniinalizing principle.
I t is found, however, not as an organic constituent, but
merely as a product in small quantities throughout the
vegetable kingdom. I t is especially noticed in the seeds of
the Graminea, in the Fungi, and in the delicate reproductive
organs, in the pollen, &c. As a rule it has been remarked
th a t its presence is constant in the young parts and organs
of plants in which there is always a high degree of vitality,
in the establishment and maintenance of which this substance
Avould appear to be an essential element. M. Peyen, in the
Memoir already referred to, lays down the following proposition
with regard to nitrogen.
“ In the two kingdoms, the bodies which admit azote to
the number of their principal constituents, are indispensable
to the accomplishment of the laws of life.”
A distinction may be established between animals and
vegetables, moreover, by a consideration of the effects of
different reagents applied to their tissue. This distinction is,
however, less satisfactory than th a t derived from a knowledge
of their chemical composition. “ Vegetable membranes,”
M. Peyen remarks, “ which are well aggregated, are not
sensibly alterable in the presence of a host of reagents, such
as iodine, chlorine, the alkalies, and acids diluted, tannin,
many neutral salts, alcohol, and creosote, which colour,
attack, dissolve, or strongly contract the membranes of
animals, but the distinction which is founded upon their
elementary composition is still more certain.”
The same agent, iodine, seems to detect the presence of the
product starch, and of the element azote, by imparting to
starch globules a blue tint, and to those substances containing
azote a yellow coloration.
A few remarks upon the subject of circulation may here
be introduced. I f we except the order Characea, to be
described in its proper place, but few traces of a circulation
in the freshwater Conferva exist. There is probably a
motion of fluid in the tubular structure which connects the
light green granules of the Alga, and in the rays which
proceed from the central organ in Zygnema ; there is also,
doubtless, an action of endosmosis and exosmosis carried on
between the different contents of the cells, and between these
and the water in which the Conferva dwell.
The uses of the freshwater Conferva may he regarded as
fourfold ; two of these uses pertain to the animal creation in
general, the other two to man in particular.
The first and most obvious use to notice Is, the abundant
supply of delicate and nutritious food which they furnish to
myriads of the inhabitants of our fresh waters. I t is scarcely