Sargassum microcystum

Thallus tough, coriaceous, to 2 m high. Main axis cylindrical, filiformis, entire, bearing several primary branches from all sides. Secondary branches branchlets and phylloids alternately branched. Phylloids at the lower part lanceolate, membranaceous, shortly stalked, with toothed margins, asymmetric at base with emarginate almost entire inner margin and with rounded apex. The upper phylloids narrowly lanceolate (2-2.5×12-17 mm). Midrib distinct prominent on both sides of phylloids, vanishing below apices. Vesicles numerous, single or in groups, spherical, oval to elliptical, small, 1-2.5 mm across, sometimes with narrow dentate wing on one side and with well visible stalk (often with spines) develop on branchlets in axils of phylloids. Cryptostomata prominent, scattered on both sides of the midrib and vesicles. Receptacles in racemose branchlets (female receptacles are triquetrous, male receptacles cylindrical, subclavate, twoedged, dentate on margins) develop in axils of phylloids. Attachment by discoid holdfast.

Indian Ocean Islands. Vietnam, Singapore, Australia.