Padina tetrastromatica

Thallus flabellate, divided into several narrow overlapping blades almost to the base, in the upper part the thallus split into small blades with inrolled edges, 7–15 cm high, 15–29 cm broad, lightly calcified, yellowish-brown, olivegreen to dark-brown, markedly zonated due to reproductive organs on both sides of narrow rows of hairs. Hairs develop in concentric bands on the lower surface of the blade. Blades in young (inrolled) portion composed of 2 cell layers (30–55 μm thick), in the middle part of 3 cell layers to 90 μm thick, and at the base of 4 cell layers to 150 μm thick. The basal part is covered by rhizoids. Tetrasporangia oval, 55–85×80–100 μm. Oogonia obovate, 100–120×80–100 μm. Attachment by stypose holdfast to low intertidal and upper subtidal rocks and dead corals, in areas with moderate wave activity.

Atlantic, Indian and Pacific Oceans. Common in Asia-Pacific countries.