Ser. GONGYLOSPEEME.E. (23) Fam. RHODYMENIACE^E. 



Plate LXXIV. 

 DUMONTIA FILIFOEMIS.— G^rer. 



Gen. Char. — Frond filiform; when old tubular, wlien young, more or lesB filled in the 

 centre with delicate anastomosing filaments ; the walls of the tube composed of 

 three strata, inner of longitudinal, articulated, anastomosing filaments, densely- 

 interwoven ; from these arise other similar short, dichotomous, vertical filaments, 



DuMONTiA JiUformis. — Frond filifoi'm, attenuated at each end, and 

 emitting on all sides, irregidarly from its lower half, long slender 

 branches, tapering to a naiTOw point, and much attenuated to the base like 

 the main stem. Favella) and tetraspores foiihed by the metamorphosis 

 of the dichotomous filaments. 



DuMONTiA filiformis.—Gvev. Ahj. Brit. p. 165, t. 17 ; Hooh. Br. Fl. vol. ii. 

 p. 308; Wyatt, Aly. Damn. No. 31 ; Hooh. fil. Fl. Ant. part 1, 

 p. 189 ; Kiilz. Phyc. Gen. p. 394, t. 74, f. 2 ; Endl. 3rd Suppl. p. 39 ; 

 Harv. in Maclc. Fl. Ilib. part 3, p. 188 ; Harv. P. B. plate 59 ; Harv. 

 Man. p. 147 ; Harv. Syn. p. 121; Atlas, plate 46, fig. 209; /. G. 

 Ayardh, Sp. Gen. Alg. vol. ii. p. 348. 



DiTMONTiA incrassata. — Lam. Ess. p. 45. 



Halymenia filiformis. — Ag. Sp. Alg. vol. i. p. 214 ; Ag. Syst, p. 245. 



Chondkia purpurascens. — Grev. Fl. Edln. p. 290. 



Gastridium fiUforme.—Lyngb. Hyd. Dan. p. 68, t. 17. 



Conferva filiformis. — Fl. Dan. t. 1480, f. 2. 



Ulva filiformis. — Wald. Fl. Lapp>. p. 508. 



Var. /3. crkpata. — Frond compressed, cm'led and twisted. 



DvMOTSTiA filiformis, crispata. — Grev. Alg. Brit. p. 165; Harv. 1. c, ; /. G. 

 Agardh, Sj). Gen. Alg. vol. ii. p. 350. 



Halymenia purpurascens, crispata. — Grev. Crypt, t. 240, 



Hab. — On rocks, stones, old shells, &c., in the sea. Annual. Summer. j3 in places 

 exposed to tidal currents. Common. 



Geogr. Dist. — Shores of Europe ; Southern Ocean. 



Desckiption. — Root, a minute disc. Fronds tufted, filiform, six to 

 twenty-four inches in length, and one to six lines in diameter, much- 

 branched from near the base to the middle ; branches simple, long, 

 slender, and, as well as the frond, much attenuated to the base, and 

 tapering to a long slender point. The branching is often veiy irregular, 

 sometimes being confined to the base, and at others entirely to the 



