F la if. CXCL.
P l a íe CXCI.
PTILOTA SERICEA, Gmel. (sp.)
Gen. Ch a e . M v n d inarticulate, linear, compressed, or flat, distichous,
pectinato-pinnate; the pinnules sometimes articulate. Fructification,
of two kinds on distinct individuals; \ , tetraspores aiiaFcLtà
to, or immersed in, the ultimate pinnules; 3, roundish, clustered
receptacles (favellæ) surrounded by an involucre of short ramuli.
P tilota (Ag.),—from imXicTos,;
Ptilota sericea ; frond flaccid, excessively branched ; secondary branches
bi-tripinnate ; pinnæ and pinnules exactly opposite, th e latter linear,
composed of a single row of cells ; tetraspores on short processes of
th e pinnules ; favellæ pedunculate, binate, naked, or surrounded with
a few n-regular ramuli.
P tilota elegans, Kiitz. Phyc. Gm. p. 378.
P tilota plumosa, var. y. tenuissima, Ag. Sp. Alg. vol. i. p. 386. Ag. Syst.
p. 195.
P tilota phrmosa, S- capUlaris, Grev. Alg. Brit. p. 155. Ilooh. Fl. Br. vol. ii.
p. 307. Wyatt, Alg. Damn. no. 77. Earv. in Mack. Fl. E ib . p a rt 3. p. 204.
Harv. Man. p. 84.
F u cu s serioeus, Gm. Hist. Fuc. p. 1 4 9 .1 .15. f. 3.
Fucu s Ptüotus, Gunn. Fl. Norv. vol. ü. p. 135. t. 2. f. 15. Esper. Ic.
p. 96. t. 46.
Fucu s pectinatus, Gunn. El. Norv. vol. ii. p. 122. t. 2. f. 8. Esper. Ic.
p. 97. t. 47.
P locamium elegans, Bory, sec. Kiitz.
H a b . On th e perpendicular faces of rooks, between tide marks ; rarely on
th e stems of Fua ts serratus. Perennial. Summer and autumn. Very
common on th e British shores.
Geogr. D i s t r . Atlantic shores of Europe, from Norway to France. East coast
of North America.
D esc r . Eoot, a small disk. Fronds tufted, two to four inches long, or more,
and as much in expansion, distichous, excessively branched, in a more or
less regularly pinnate manner, th e main divisions only being somewhat
dichotomous ; secondary branches elongate, repeatedly and closely pinnate,
th e pinnæ and pinnulæ nearly horizontally patent, of very frregular lengths,
short and long being intermixed consecutively without order ; the longer
again and again pinnated, the shorter simple. Vltimate pinnulæ very closely
set, those on the outer side of the pinnæ longer than the. inner, linear,
blunt, slightly curved, articulated, composed of a single row of quadrate
cells ; the older ones emitting pinnules of a second order at each joint, iu
which case the cells of the main pinnule acqnfre an invertly pyriform shape
(owing to the excavation of two lateral huds). Tetraspores spherical, with
wide borders, borne on th e lateral processes of the pinnules. Eaveïlæ on
i f