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Ser. R h o d o sp e rm eæ . Fam. Bkodomelece.
P l a t e CCXXVIII.
POLYSIPHONIA GRIFFITHSIANA, H a r v .
Gen. C h a r . Frond filamentous, partially or generally articulate; 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), furnished with a terminal
pore, containing a mass of pear-shaped spores; 3„ tetraspores imbedded
in swollen branchlets. P o ly s ip h o n i a {Grev) ,—from ttoXds,
and o-i0a>v, a tube.
P o ly s ip h o n i a Griffithsiana ; stem rigid, attenuated, alternately branched ;
branches long, patent, subsimple, furnished with numerous subdioho-
tomous or alternately divided, slender, patent, flaccid ramuli ; articulations
of the stem, branches, and ramuli about once and a haK or rarely
twice as long as broad, with straight tubes ; siphons in the stem four,
with four alternate secondary ones ; capsules broadly ovate, sessile.
P olysiphonia Griffithsiana, Harv. Man. p. 91.
H a b . On the smaUer Algæ between tide-marks. Annual. September.
Parasitical on Poh/ides rotundus at Torquay, Mrs. Griffitlis. Isle of
Portland, Miss White.
Ge o s e . D is t e . South coast of England.
D e sc e . Moot a small disc. Fronds laxly tufted, four to five inches long, and
nearly as much in expansion. Stem undivided, set throughout its length
with alternate, spreading branches, the lowest of which are longest, the rest
gradually shorter upwards, giving the whole frond a pyramidal outline.
Branches like the stem, beset with a second and third series of alternate lesser
branches, the last of which are more or less furnished with dichotomous, flaccid,
slender ramuli. All parts of the frond are conspicuously jointed ; the articulations
of the stem are from one and a half to twice as long as broad, marked
with about five tubes, two of which are much narrower than the rest ; those of
the branches are about once and a half as long as broad, with two tubes
only. A transverse section of the stem shows four primary and four
secondary tubes. Ceramidia ovate, sessile, scattered on the ramuli. Colour
a full red, inclining to brownish in drying but not much altered by fresh
water. Substance rather rigid in the stem and branches, flaccid in the
ramnli.
An elegant plant with a good deal the habit of small specimens
of P. violacea, but known at once from that species by the distinctly
jointed stem marked by straight tubes. It moreover resists
the action of fresh water for a longer time, and the colour is also
different. Some specimens of P. elongella have a slight look of
2 D 2