Sargassum oligocystum

Thallus coarse, leathery, densely branched, dark brown, bushy, 10-40(-50) cm high. Main axis short, flattened above, 2-3 mm diam., 5 mm high, giving rise to several primary branches. Primary and secondary branches smooth, flattened, 2.5-3(-4) mm broad. Branching alternate, distichous. Phylloids oval, oblong to lanceolate, slightly cuneate at base, 3.5(-6) cm long, to 10 mm broad; midrib percurrent; apices obtuse, margins smooth or irregularly toothed. Vesicles stalked, spherical, subspherical to ellipsoid 4-7(-10) mm diam. with apices rounded, apiculate or sometimes winged; stalk foliaceous with midrib and dentate margins. Cryptostomata scattered on both sides of the midrib, vesicles and stalk. Receptacles compressed, forked, to 7 mm long, with spinulose margins, develop in clusters at base of phylloids. Holdfast irregular disc-like. Growing on lower intertidal to subtidal rocks, dead corals.

Tropical and subtropical waters of Indian and Pacific Oceans. Common in countries of the Asia-Pacific Region.