Ser. RuoposrerMEX. Fam. Sphaerococcoidea. 
Prats CCCVII. 
RHODYMENIA CRISTATA, Grev. 
_ Gey. Cuan. Frond flat, membranaceous or subcoriaceous, ribless, veinless, 
cellular ; central cells of moderate size, those of the surface minute. 
Fructification: 1, convex tubercles (coccidia), having a thick, cellular 
pericarp, and containing a mass of minute spores; 2, ¢etraspores, 
either zoned or tripartite, imbedded among the cells of the surface, 
scattered, or forming cloudy patches. Ruopymenta (Grev.),—from 
podeos, red, and ipny, a membrane. 
RuopyMenta cristata; frond fan-shaped, membranaceous, subdichotomous, 
the segments dilated upwards, repeatedly subdivided ; lesser divisions 
alternate, linear, lacimiate at the ends and often fimbriate at the 
margin; tubercles spherical, marginal, sessile. 
RHODYMENIA cristata, Grev. dig. Brit. p. 89. Hook. Br. Fl. vol. ii. p. 290 
Harv. Man, ed. 2. p.126. Endl. 3rd. Suppl. p. 210. 
CaLLOPHYLLIS cristata, Kitz. Sp. dg. p. 747. 
SPH#ROCOCCUS cristatus, dy. Syn. p. 29. Lyngb. Hyd. Dan. p.13.t.4. Ag. 
Sp. Alg. vol.i. p. 300. Ag. Syst. p. 231. Hook. Fl. Scot. part 2. p. 104. 
Grev. Crypt. Scot. t. 85. Fl. Edin. p.296. Kitz. Phyc. Gen. p. 410. 
Fucus cristatus, Herb. Linn. Turn. Hist. t. 23. 
Fucus gigartinus, #7. Dan. t.394. Mohr, Hist. Isl. p.247. Gunn. FI. 
Norv. n. 847. 
Has. Growing on the roots and stems of Laminariz in deep water, very 
rare. Annual. July. Sea-shore at Wick, Caithness, Messrs. Hooker 
-and Borrer, Frith of Forth, Dr. Grenille. Berwick, Dr. Johnston. 
Shetland, at Bressay, in fourteen fathoms, Prof. 2. Forbes. Several 
stations in the Orkney Islands, in 8-10 fathoms, Lev. ee and 
Dr. M‘Bain. 
Geocr. Distr. Arctic Sea, and shores of the North of Europe. Iceland. 
Eastern shores of North America, as far south as Cape Cod. 
Descr. foot minute, discoid. Fronds in British specimens from half an inch 
to an inch, rarely two inches long, in American from two to four or five 
inches, from one to three or four lines in breadth, fan-shaped or semicir- 
cular in outline, sometimes quite fastigiate, sometimes irregularly divided, 
some of the branches far out-topping the others, excessively branched from 
the base. Branches linear, or slightly broader upwards, subdichotomous, 
but very irregular in division ; sometimes alternately divided, sometimes 
secund, and sometimes fingered, or branched in a manner compounded of 
all these. The lesser divisions are usually bordered with slender, jagged 
