RHODYMENIA. 125 



On rocks and Algae, in the sea. Annual. Summer. Frequent on the 

 shores of England and Ireland ; rare in Scotland. Fronds thin and deli- 

 cate, 1 or 2 inches high, tufted, irregularly dichotomous, the axils rounded ; 

 the segments linear or somewhat wedge-form, 1 3 lines wide ; the apices 

 rounded or truncate. The margin is either entire, or fringed with minute 

 processes which sometimes become branches. Tubercles globose, either 

 marginal, or rarely scattered over the surface of the terminal lobes. Te- 

 traspores transversely zoned, forming cloudy spots on the upper segments, 

 both marginal and scattered. Colour a fine rose-red ; substance transpa- 

 rent and delicate, nearly as thin as in Nitophyllum ; but the cellules are 

 smaller and denser, and the fructification very different. 



2. R. laciniata, Huds. ; frond thickish or sub-cartilagi- 

 nous, opaque, bright red, more or less palmate or flabelli- 

 form, cleft into numerous, broad, wedge-shaped segments, 

 which are again divided in a sub-dichotomous manner ; 

 the apices obtuse ; the margin, when in fructification, fringed 

 with minute cilia, in which the tubercles are imbedded. 

 Grev. Alg. Brit. p. 86 ; Hook. Br. Fl. ii. p. 289 ; Wyatt, 

 Alg. Danm. No. 17 ; Harv. Phyc. Brit. t. cxxi. F. lacinia- 

 tus, E. Bot. t. 1068. 



On rocks and stones, in deep water. Biennial ? In fruit from January to 

 July. Fronds rising from a disk, several from the same base, 3 10 inches 

 long, with a short, flat stem, which soon expands into a deeply cleft frond, 

 divided in a dichotomous manner, the segments all becoming broader up- 

 wards, varying in width from half an inch to 3 or 4 inches ; the apices ob- 

 tuse, but frequently lacerated. When bearing tubercles the margin is 

 closely fringed with minute ciliary processes, in which the tubercles are 

 placed. Telraspores, tripartite or cruciate, forming cloudy spots along the 

 margin, which is then smooth and entire. Substance soft, between carti- 

 laginous and membranaceous, adhering to paper. Colour a fine blood red, 

 glossy when dry. 



3. R. Palmetto,, Esper. ; stem cylindrical, sub-simple, ex- 

 panding into a fan-shaped, rose-red frond, which is more or 

 less cleft in a dichotomous manner ; the segments wedge- 

 shaped ; axils rounded ; apices (according to the state of 

 fructification), either erose or rounded ; tubercles mostly ter- 

 minal ; spots of tetraspores in the expanded tips. Grev. Alg. 

 Brit. p. 88, t. 12 ; Hook. Br. Fl. ii. p. 290 ; Wyatt, Alg. 

 Danm. No. 109 ; Harv. Phyc. Brit. t. cxxxiv. F. Pal- 

 metta, E. Bot.t. 1120. 



On rocks, or the stems of Laminaria digitata. Annual. Summer and 

 autumn. Stem cylindrical, filiform, becoming compressed upwards, half 

 an inch to 2 inches long, simple, or with one or two branches, expanding 

 into a fan-shaped frond, 1 or 2 inches across, deeply divided in a di- 

 chotomous manner. In specimens communicated by Miss Cutler, there is 

 scarcely any stem, and the frond is simply forked, its segments linear and 

 not a line in breadth ; and in others from the same lady, once-forked, 



