Description: Thallus a broad flat membrane two cells thick, growing to a length of 50 cms. The blade often lobed, undulate, devided or torn. Cells are more or less well arranged in slightly curved rows usually with one pyrenoid.

Habitat: Common. Epilithic or epiphytic on other algae in rock pools of the littoral and in the sublittoral.

Distribution: Widespread around the shores of the British Isles, distribution generally world-wide.

Similar Species: All species of Ulva and Umbraulva olivascens are two cells thick and similar. Enteromorpha and Monostroma are also similar but one cell thick.

Key Identification Features:

• Large flat blade, two cell thick. Umbraulva olivascens is rare, olive green in colour and the cells are mostly irregularly arranged. Ulva rigida has microscopic teeth at the edge of the frond near the base.

Distribution Map from NBN: Ulva lactuca at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Ulva lactuca at iNaturalist World Species Observations database.

WoRMS: Ulva lactuca at World Register of Marine Species. Accepted name: Ulva lactuca Linnaeus, 1753. AphiaID: 145984.

Classification: Biota; Plantae; Viridiplantae; Chlorophyta; Chlorophytina; Ulvophyceae; Ulvales; Ulvaceae; Ulva