Ser. RHODOSPERME. Fam. Ceramiee. 
Pirate CCLXXIV. 
CALLITHAMNION ARBUSCULA, Zyngé. 
Gen. Cuan. Frond rosy or brownish-red, filamentous; stem either opake 
and cellular, or translucent and jointed ; branches jointed, one-tubed, 
mostly pinnate (rarely dichotomous or irregular); dissepiments hyaline. 
Fruit of two kinds, on distinct plants; 1, external ¢etraspores, scat- 
tered along the ultimate branchlets, or borne on little pedicels; 2, 
roundish or lobed, berry-like receptacles (favel/2) seated on the main 
branches, and containing numerous angular spores. CALLITHAMNION 
(Lyngb.), from xaddos, deauty, and Oapnovr, a little shrub. 
CALLITHAMNION arbuscula; stems naked below, inarticulate, robust, carti- 
laginous, the main divisions set with shorter branches, which are 
densely clothed on all sides with minute, imbricated, pinnated ramuli 
(plumules) ; ultimate pinnules simple or forked, recurved, acute, 
articulated, the articulations twice as long as broad; tetraspores glo- 
bose, numerous, sessile on the upper edge of the pinnules. 
CALLITHAMNION arbuscula, Lyngd. Hyd. Dan. p.123.t.38. Harv. in Hook. 
Br. Fl. vol. i. p. 340. Harv. in Mack. Fl. Hib. part 3. p. 213. Hare. 
Man. ed. 1. p.105. 
PHLEBOTHAMNION arbuscula, Kiite. Sp. Alg. p. 656. 
Dasya spongiosa, 4g. Sp. Alg. vol. ii. p. 121. 
ConFERVA arbuscula, 2. Br. — Dillw. t. 85. (excl. t.G.) #. Bot. t. 1916. 
Has. On rocks and mussel-shells, near low-water mark, usually in places 
left bare on the recess of the tide; also in tide-pools. Perennial. 
Summer and autumn. Abundant on the western shores of Scotland 
and Ireland ; rare on the eastern. Frith of Forth, Drs. Greville and 
Arnott. Aberdeen, common, Dr. Dickie. Orkney, Rev. J. H. 
Polleafen. 
Groer. Distr. The Ferroe Islands (and probably elsewhere in the Northern Sea). 
Descr. Root a fleshy, conical disc. Fronds several from the same base, from 
two to five or six inches high, as thick as small twine below, attenuated 
upwards, opake, and without visible articulation, much branched and shrub- 
like. Stems naked below, densely set with lateral branches above, and 
these furnished with other smaller ones, spreading on all sides and making 
a bushy or shrub-like head. The lesser branches, which are from a quarter 
to half an inch in length, are densely clothed with minute, closely imbri- 
cated plumules, a line or two in length, which make each little branch 
cylindrical, and, being very dense towards the tips, give the apices of the 
branches a strikingly blunt, corymbose aspect. The plumules have a flexuous 
rachis, set with alternate, simple, or once forked, horizontally patent or 
reflexed pinnules. Favelle of small size, binate or clustered, springing 
from the rachis of the plumules. Tetraspores sessile, spherical, of small 
