78 RHODOMELA. 



1. O. dentaia, L. ; frond vaguely branched in an irregu- 

 larly pinnate manner ; branches linear-oblong, narrowed at 

 base, pinnatifid ; lacinia? alternate, sharjjly toothed at the 

 truncate extremities ; capsules clustered on branched pedun- 

 cles. Grev. Alg. Brit. p. 101, t. 13; Hook. Br. Fl. ii. p. 

 293 ; Harv. PIujc. Brit. t. xxxiv. Fucus dentatus, E. Bat. 

 t. 1241. 



On rocts in the sea. Perennial. Fruiting from January to March. 

 Frequent on the shores of Scotland, and of the north of England and 

 Ireland. — Fronds rising from a hard disk, tufted, 3 — 12 inches long, much 

 branched, furnished with an imperfect midrib toward the base, flat and 

 membranaceous above; the main stem simple or forked, 2— 4 lines wide, 

 narrower at base, alternately toothed ; branches issuing from the axils of 

 the teeth of the main stem, attenuated at base, simple, or somewhat pal- 

 malely divided, and either toothed or pinnatifid, the lobes in the latter case 

 being toothed, and, as they become larger, pinnatifid. The frond preserves 

 throughout nearly the same breadth, rarely exceeding 4 lines. Fructifica- 

 tion borne along the margin on very slender pedicels, which are either 

 simple or branched ; ceramidia ovate, containing a cluster of pear-shaped 

 spores, which are finally discharged through a terminal pore ; stichidia 

 lanceolate, containing a double row of ternate tetraspores. Substance car- 

 tilagineo-membranaceous, scarcely adhering to paper ; structure densely 

 cellular. Colour a deep vinous red, becoming darker in drying. 



II. Rhodomela. Ag. [Plate 11, B.] 



Frond filiform, solid, much branched, inarticulate, reticu- 

 lated ; the axis composed of concentric layers of oblong, 

 hyaline cells ; the periphery of several rows of minute, irre- 

 gular, coloured cellules. Fruciijication twofold, on distinct 

 plants ; 1, ceramidia, containing a tuft of pear-shaped spores ; 

 2, tetraspores contained in lanceolate pot/.? (stichidia) or in 

 swollen branchlets. Name, poho^ red and jttEXaj, black ; be- 

 cause these plants become darker in drying. 



I. R. lycopodioides, L. ; frond elongate, mostly simple, 

 densely beset with slender, finely divided branchlets, mixed 

 with the short, rigid, bristle-like remains of a former series. 

 Grev. Alg. Brit. p. 102; Hook. Br. Fl. ii. p. 294; Harv. 

 Pliyc. Brit. t. 1. Fucus lycopodioides, E. Bot. t. 1163. 



On the stems of Laminaria digitata. Perennial. Summer. Common 

 on the shores of Scotland and of the north of England and Ireland. — 

 Fronds 4 — 18 inches long, tufted, filiform, attenuated upwards, simple or 

 subsiniple, clothed, in its winter state, with short, rigid, simple or slightly 

 branched ramuli, half an inch to an inch in length ; in summer throwing 

 out from these and the main stem numerous capillary, multifid, slender ra- 

 muli, usually 1 or 2 inches long, but which, in some magnificent specimens 

 gathered by my friend Mr. W, Thompson, at Bangor, Co. Down, arc 



