Sargassum johnstonii

Sargassum johnstonii Setchell et N. L. Gardner

Sargassum johnstonii Setchell et N. L. Gardner, 1924a:737, pl. 20: fig. 72, pl. 21: fig. 80; Setchell and Gardner, 1925:719; Dawson, 1944:240, pl. 23: figs. 1–15, pl. 33: figs. 1, 2, 17–22; Dawson, 1961b:400; Dawson, 1966a:12; Norris, 1973:7, pl. 13; Huerta-Múzquiz, 1978:337; Littler and Littler, 1981:151, tbl. 3, figs. 4, 5, 7; McCourt, 1984a:142; McCourt, 1984b:141; Mendoza-González and Mateo-Cid, 1985:26; Mendoza-González and Mateo-Cid, 1986:421; Rocha-Ramírez and Siqueiros-Beltrones, 1990:19; Rocha-Ramírez and Siqueiros-Beltrones, 1991:26; Espinoza-Ávalos, 1993:333; Phillips, 1995:118; González-González et al., 1996:161; Pacheco-Ruíz and Zertuche-González, 1996b:171; L. Aguilar-Rosas et al., 2002:235; Mateo-Cid et al., 2006:50, 58; Pacheco-Ruíz et al., 2008:205; Pedroche et al., 2008:95.

Sargassum guardiense Setchell et N. L. Gardner, 1924a:723, pl. 19: fig. 64; Setchell and Gardner, 1925:713; González-González et al., 1996:160.

Algae with several erect axes, up to 1(–2) m long, arising from a perennial, parenchymatous, disc-shaped to spreading crustose holdfast. Axes and branches terete and smooth. Leaf-like blades narrow, lanceolate to linear, slightly compressed to flattened, up to 10 mm long and 0.5–1.5 mm wide; margins smooth to sparsely dentate; without a midrib and with few to many cryptostomata. Vesicles on short pedicels, subspherical to elliptical, up to 4 mm long and 1 mm wide; apiculate with foliaceous crests or extensions, up to 5 mm long.

Receptacle branchlets narrow in diameter, branching up to 4 orders, dentate in varying degrees. Antheridial receptacles smaller in diameter than oogonial receptacles.

HABITAT. On rocks; high to low intertidal; occasionally shallow subtidal.

DISTRIBUTION. Gulf of California: El Tornillal to Bahía de La Paz. Pacific coast: Baja California Sur.

TYPE LOCALITY. Isla Jorge (George’s Island), off Sonora, Gulf of California.