the frond. Wlien tlie cylindrical receptacles are fully ripe, they fall
oft, and leave the frond truncated, as if, to use Mr Turner’s words,
tlie apices “ had been laid together and chopped off at once with a
knife; out of these rise new shoots, at first much more thin than the
rest of the frond, giving the plant that annulated appearance which
has been often noticed by authors.” Mr Turner is perfectly correct
in saying that the ovate-lanceolate transparent tips also fall off. I
have, however, seen them elongate into healthy branches, and pointed
them out to Mrs Griffiths, at Sidmouth. If, therefore, they are to be
regarded as imperfectly developed receptacles (or pods), they are still
capable, under favourable circumstances, of being converted into a
continuation of the frond in its ordinary state.
In a barren state it is very difficult to distinguish this plant from
Polyides rotundus without examining the root.
O r d e r V I I I .— S P O N G IO C A R P E Æ .
Pkadft marine, o f a dull, dark reddish purple colour, changiny
to nearly black cm exposure to the air, cai'tilaginous substance,
and cellular structure. Hoot scutate. Frond filiform, cylindrical,
and dichotomous. Fructification uniform, consisting
o f naked spongy warts composed o f a mass o f radiating fila ments,
among which are imbedded numerous roundish clusters
o f seeds, surrounded with a pellucid border ; the seeds wedge-
shaped, fix ed by their base to a central point.
Obs. The fructification of the genus Polyides is so peculiar, that I
know not any other with which it has the most remote affinity, and I
therefore propose to consider it as the type of a distinct family. In regard
to the mere habit of growth, it is similar to the genus which also
stands alone in the preceding order. The colour of the frond, the nature
of the seeds, and the general structure, indicate its situation in a
system to be near the F l o r id eæ .
G e n u s X X III. POLYIDES, Ag. Tab. XI.
Ge n . Ch a r . Frond cartilaginous, filiform, cylindrical. Fructification
naked spongy warts, composed of radiating
filaments, among which are imbedded roundish clusters
of wedge-shaped seeds, surrounded with a pellucid border.
Obs. One of the most distinct genera of Algce, separated about the
same time by Professor Agardh, under the name of Polyides, and by
myself under that of Spongiocarpus ; the former has the priority, and is
derived from two Greek words, signifying many forms or appearances.
It is therefore scarcely applicable, as the only well-known species is
tolerably constant to all its characters. In an earlier work Agardh
made it a species of Chordaria; Lyngbye considered it a Furcellaria ;
Lamouroux a Gigartina ; all equally pmote from the truth. The
peculiar characteristic is the spongy wart-like fructification. When
carefully examined with the aid of a microscope, the internal structure
of the frond is perceived to be cellular ; but the cellules are elongated
aud arranged in such a manner as to have the appearance of filaments,
especially in the centre, and towards the circumference. Many are
constantly inclining in a curve towards the circumference, where they
terminate, and constitute a dense coloured stratum. During the developement
of the fi-uctification, these filaments are prolonged, become
branched, and produce, here and there on the frond, spongy masses,
within which are roundish clusters of wedge-shaped seeds, fixed by their
base to a central point. My late correspondent. Captain Carmichael of
Appin, who was remarkable rather as an indefatigable collector, than
correct observer of plants, maintained that the spongy fructification of
Polyides ought to be regai-ded as a distinct-and parasitic Alga ;—an
opinion easily proved to be erroneous by microscopical examination,
and which the very nature of the seeds might have convinced him
was untenable.
In sterile plants, globular white masses are freely deposited in the
cellular tissue towards the circumference of the frond, and are easily
broken down into minute spherical grains. They are very obvious
when a thin transverse slice is placed in the microscope. The grains
resemble those with which the cellules of the barren frond of Rhodomela
subfusca are sometimes filleii.
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