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P l a t e LXXI.
PEYSSONELIA DUBYI, Crouan.
Gen. Chau. Frond, brownish red, depressed, rooting by the under surface,
concentrically zoned, composed of several rows of cellules, disposed
obliquely in fllamentous series. Fructification; warts scattered over
the upper surface of the frond, formed of radiating filaments, and
containing oblong, cruciatoly divided tetraspores. P e v s s o n e l i a {Dne.)
—in honour of J. A. Peyssonel, an early and meritorious observer of
marine plants, especially of Corallines.
F b y s s o n b l i a Duhyi ; frond membranaceous, orbicular or lobed, attached
bv the whole of its under surface.
P ey s s o n e l ia Diibyi, Crouan, in An. Sc. Nat. 1 8 4 4 . p. 3 6 8 . t. 1 1 . B .
IJab. On old shells, stones, &c., in 1 0 -lB fathoms water. Probably common
on the British coasts. North of Ireland, Mr. Thompson. Bir-
turbui Bay, on the Scallop bank, Mr. Me’ Calla. West of Scotland,
Bev. D. Landsboroiicjh.
G e o g e . D i s t u . Coast of Normandy, Crouan, (probably on aU tbe Atlantic
shores of Europe?).
D e s c e . Frond, from half an inch to an inch and a half in diameter, at first orbicular,
in age becoming frregularly shaped, with a lobed or wavy margin, the
lobes here and there overlapping each other, membranaceous, thin, concentrically
zoned, attached by the whole of its under suiiace, by means of
short, slender, colourless," rooting processes, wbicb form a laxly disposed
pubescence, extending over the lower surface. A vertical section of the
frond exhibits a cellular structure, the cells arranged in ascending filamentous
series, of wlhcb those near the centre of the frond are nearly vertical, and
become more oblique as they approach the margin. Fructification, spongy
wai-ts, scattered over the upper surface, composed of pale filaments, similar
except in colour, to those that compose the frond, among which are disposed
vertical, eUiptic-oblong tetraspores, the endrochrome of which divides
at maturity, by lines crossing tio « at rDig_h_t _a_n_g_l_e_s_, oi o , into fom-equal parts. Colour,
a dull brownish red. Suhstance membranaceous.
TBe species here figm-ecl is an instance among many that
might be mentioned, of one of those obscure plants which escape
the attention of coUcctors, but wbicb, when once pointed out,
are found to be very common, and even to liavo beeu noticed
and neglected by many persons, long previously to tbeh having
been found by the individual who has rescued them from oblivion
by giving them a name. To whom in sucb cases attaches the