148 COLLINS AND HERVET. 



of a cell, ending below in a larger or smaller disk. Erect filaments 

 cylindrical or very slightly tapering, issuing from the upper surface 

 of the prostrate filament, near the middle of a cell, usually opposite 

 a rhizoid, 24-30 ju diam., walls 2-3 fx thick, lower cell 2-2| diam. 

 long, other cells 3-4 diam. long, terminal cell rounded; erect filaments 

 sometimes unbranched, sometimes with a few alternate or secund 

 branches near the apex. Fructification unknown. On rocks between 

 tides, cave, Agar's Island, Aug., Nov., Collins. 



This plant forms a plush on flat rocks a little above low water mark, 

 as does R. Rothii (Turton) Nag. in similar stations on the shores of the 

 North Atlantic, and its manner of branching resembles that of the 

 latter species but its dimensions are about double. We have ex- 

 amined many specimens of R. Rothii, from both coasts of North Amer- 

 ica as well as from Europe, and find very little variation in size among 

 them. In R. spehmcarum the chromatophores are numerous small 

 granules, usually densely packed, occasionally looser and showing 

 something like a network. Type in Collins herbarium. No. 8401, 

 Nov. 23, 1915. 



2. R. MEMBRANACEUM (Magnus) Hauck, 1885, p. 69; CaUitham- 

 nion memhranaceuvi Magnus, 1874, p. 67, PI. II, figs. 7-15. In bryo- 

 zoans. Bethel's Island, Dec, Collins. 



Family GRATELOUPIACEAE. 

 Halymenia Agardh. 



1. Frond many times dichotomous, digitate, cylindrical. 4. H. Agardhii. 

 1. Frond plane, simple or proliferous. 2. 



2. Thin, not gelatinous. 1. H. bermudensis. 



2. Thicker, gelatinous. 3. 



3. Large echinate cells in subcortex. 2. H. echinophysa. 



3. Few or no echinate cells in subcortex. 3. H. pseudofloresia. 



1. H. bermudensis CoUins & Howe, 1916, p. 169; P. B.-A., No. 

 2050; Plate V, fig. 34, plate VI, fig. 37. In shallow water in clefts of 

 rocks and among roots of mangroves, often in loose, unattached 

 masses. Kemp. Aug., as Rhodyvienia j^ahnata; Walsingham, Feb., 

 Farlow; Oct., Miss Peniston; near Hamilton, June, Tucker's Town, 

 July, Howe; Green Bay, March, ^Yadsworth; Harrington Sound, 

 Jan., Tucker's Town, Feb., Dec, Dingle Bay, March, Grasmere, 



