Ulva pertusa

Thallus membranous, rigid, bright green 8(-40) cm high, variable in shape, often rosellate, irregularly lobed, deeply split into blades (almost to the base). Blades flat or ruffled, 75-85(-170) mm thick at base and 50 mm near margins, sometimes with holes in the middle part. Margins entire or undulate. Cells in surface view irregular rounded polygonal, (7.5)-10-15(-20) × 12.5-17.5(-30) mm, sometimes in series of paired cells. In transverse section cells roundish to palisade-like, vertically elongated (to 32 mm high). Pyrenoids 1-2 per cell. Holdfast small, inconspicuous, disc-like in the middle of thallus. Growing on hard substrate forming extensive mats in the upper and middle intertidal zones, often colonizing damaged corals.

Temperate, subtropical and tropical waters of Indian and Pacific Oceans.