Fam. x i i i . OSCILLATOREÆ.
Tlie family of Osdllatoreoe, limited to the genera Oscillatoria
and Microcoleus, is one of the most distinct and remarkable
of the divisions of the Algæ. The majority of the
species are characterized by the minuteness of their filaments,
the equality of their calibre, and their mathematical
rectitude or straightness ; they are still further distinguished by
the brevity of their cells, the ease with which these separate
from each other, the wonderful rapidity of their growth, the
surpassing brilliancy of tlieir colours, and lastly, by a peculiar
oscillation, upon whicli feature their generic name has been
founded, bu t with regard to which I can myself perceive
nothing extraordinary, although the phenomenon is certainly
peculiar to this family — nothing indicative, as most suppose,
of a sensitive or animal life. The explanation to be given
of this oscillation of the filaments I consider to be partly of
an external, and entirely of a physical character. I t has been
stated tha t the filaments of very many species of Oscillatoria,
and indeed of all those which present the phenomenon of
oscillation, are remarkable for their straightness or rectitude,
which is due to a certain degree of elasticity belonging to
them, and which leads to the effort on their part, whenever,
as on being placed for observation on the field of the microscope,
must be the cash, they are bent or put out of a straight
line, to recover tha t position which is natural to them. This
elastic property of the filaments, currents almost imperceptible
in the liquid in which they are immersed, and perhaps
unequal attractions amongst the filaments themselves, are
causes amply sufficient to explain any motion which I have
ever witnessed amongst the Oscillatorioe, and which motion I
cannot help thinking to have been misunderstood and exaggerated
to such an extent, as to throw around these plants an
unnecessary degree of mystery.
Upon the reproduction of this family, and some others
which follow, no very precise observations appear to have
been made. Vaucher remarking the ease with which the cells
or ‘ rings separated from each other, supposed them to be
multiplied by means of these. This separation, however, is
probably merely to he regarded as a preparatory step, the
true reproduction being by means of zoospores.
Gerod Chantrans * makes some observations upon the reproduction
of the Oscillatorioe. He states tha t when an
Oscillatoria has reached its complete developement, it emits
from its cells a granulated powder, each grain of which
increases insensibly until finaUy it becomes developed into
a perfect plant. In this account, Gerod Chantrans has not
swerved far from the truth.
The species of this family are found under very different
circumstances; upon the moist earth, in stagnant, still, and
running waters; in medicinal waters, and in such as are
absolutely hot and almost boiling. They are, with very few
exceptions, highly mucous to the touch, and in some kinds
the hlaments are imbedded in a mucous nidus.
The brilliancy of their colours has been noticed. The
tints are various, shades of bright and beautiful greens, many
presenting a metallic or æruginous cast, of violet, purple,
dark brown and glossy black.
No description of a species can be considered perfect, unless
It be taken from an examination of specimens, both in
the recent and dried state, the characters not being identical
in these conditions,
A monograph on this family, the result of two or three
years’ patient and careful observation, is much needed.
29. O SC IL LA TO R IA .
Char. Filaments simple, even, elastic, closely striated, and often ■
lying in a mucous matrix.
Derivation. From oscillo, to vibrate,
* Recherches Chimiques et Microscopiques sur les Conferves, &c.
Æaris, an x. ’
R 3