P l a t e CIL A.
POLYSIPHONIA OBSCURA, J. Ag.
Gen. Chak. Frond fflamentous, partially or generally a rticulate; joints longitudinally
striate, composed of numerous radiating cells or tubes
disposed round a central cavity. Fructification two-fold, on different
individuals; 1, ovate capsules {ceramidia), furnisbed with a terminal
pore, and containing a mass of pear-shaped spores. 3, tetraspores
imbedded in sw'ollen branohlets. P olysiphonia {Orev.), from ndkis,
u, an d (Tipav, a tube.
P o ly s ip h o n ia obscura ; densely matted together, filaments creeping, throwing
up erect, simple, secund branches, which are either naked or fu rnished
ivith a few seound ramuli ; articulations as long as broad, many-
tubed.
P olysiphonia obscura, / . Ag. Alg. Medit. p. 133. Endl. 3rd 1 p. 44.
H utchinsia obscura, Ag. Sp. vol. ii. p. 108.
CoNPEKVA intertexta. Both, Cat. Bot. vol. i. p. 188. t. 3. f. 5. vol. ii. p. 314.
H a b . Spreading over marine rocks, a t haK-tide level ; also parasitical on
Fuci, and on some of th e smaUer Algæ. Jersey, M iss White, On
th e sheltered side of a lofty rock, near Sidmouth, R e v . M r. Cresswell.
Geogb. D istk. Coast of Spain, at Cadiz, Ag, Adriatic Sea.
Desck. Plant spreading over tlie sui-face of rocks, in patches of six inches to a
foot in diameter, covering the roots of such Eu d as it may encounter. Eilaments
decumbent, attached by means of rooting processes, which issue at
intervals from the lower surface, subsimple, throwing up from the upper
surface erect, secund branches, from a quarter to half an inch in length,
quite simple, and tapering to a fine point, naked, or furnished with three
or four secund simple ramuli. Articulations visible in all parts of the frond,
about as long as broad, or rather shorter, composed of twelve or thh-teen
radiating tubes. The fruit I have not seen on British specimens. Colour,
dark brown-red. Suhstance rigid, imperfectly adhering to paper.
This interesting addition to the British Flora, was made by
Miss White, who detected, in 1846, a single specimen growing
among the roots oi B . fihrata, zY Jersey. More recently it has
been gathered in great abundance by the Rev. Mr. Cresswell, in
a station near Sidmouth, and to his kindness I am indebted for
numerous specimens, gathered at various seasons.
I had, at first, confounded it with B. secunda, Mont., a plant
to which, outwardly, it bears a strong resemblance, but from
which it differs in the length, and composition of the articulations.
I have now minutely compared the British specimens with
one of P. obscura, received from Prof. J. Agardh, and find them
to agree in all essential particulars ; ours are, however, rather
more robust than the Adriatic plant, and the joints slightly
shorter.
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