Rosenvingea orientalis (J.Agardh) Børgesen

Scientific Description

Habit and structure. Thallus erect, olive brown, soft and lax, to 15 cm tall; branching mostly subdichotomous, divaricate (almost cervicorn), interdichotomies 1.5–5 cm. Axes 1–3 mm in diameter, tubular, with acuminate apices. Structure with central cavity and frond wall 3–5 cell layers thick, this with an inner layer of large hyaline medullary cells ± 50 µm in diameter, grading to an outer epidermal layer of pigmented cells. Epidermal cells longitudinally aligned, somewhat irregularly shaped, 10–15 µm long and 4–7 µm wide in surface view. Hairs present, growing in small clusters from frond surface, 4–7 µm in diameter.

Reproduction. Reproductive structures not observed.

Distribution. Widespread in tropical regions of the Indo-Pacific and Atlantic Oceans. In W. Aust., it occurs south to the Swan River Estuary.

Habitat. R. orientalis grows on rock in the intertidal and shallow subtidal, usually associated with sand.