Sargassum podacanthum Sond.

Scientific Description

Habit and structure. Thallus medium to dark brown, 10–35 cm high, with a simple or branched stipe 1–4 cm long, terete, 1–2 mm in diameter, with stubby branch residues, bearing apically 1–3 primary branches. Holdfast discoid-conical, 2–10 mm across, with a single stipe. Primary branches 10–35 cm long, axes compressed below, terete to angular above, usually with short, scattered spines, radially branched. Laterals (lower) 1–4 cm long, 3–5(–8) mm broad, simple, lanceolate, serrate, costate throughout, with more or less prominent cryptostomata, with acute or rounded apices; upper laterals 1–2 cm long, 1–2(–3) mm broad, lanceolate, serrate and costate. Vesicles axillary, petiolate, subspherical, 2–4 mm in diameter, mutic.

Reproduction. Thalli monoecious. Receptacles bisexual, simple or branched, in clusters 3–5 mm long, terete to slightly compressed, 700–1500 µmbroad, slightly verrucose, with prominent, relatively massive, irregularly placed spines on most receptacles, apices rounded, with scattered ostioles. Conceptacles unisexual; oogonia sessile, subspherical to ovoid, 150–240 µmlong and 100–180 µmin diameter, few per conceptacle; antheridia sessile or on branched paraphyses, clavate to ovoid, (14–)16–26 µmlong and (8–)10–18 µmin diameter.

Distribution.From the Houtman Abrolhos, W.Aust., to Port Noarlunga, S. Aust.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 444 (1987)]