Ulva lactuca

Thallus sheet-like, solitary or aggregated,simple or splitted into lobes, orbicular, elongated oval or irregular in shape, lightgreen, to yellowish-green, to 1 m long. Blades flat or ruffled, often with perforations, with smooth, undulate or folded margins, with cuneate or cordate base, sessile or on short cylindrical stipe. Cells in surface view irregular rounded, polygonal or rounded-polygonal, 10-27×(20)-22-47 mm, disordered. In transverse section, blade 100-200 mm thick at base and 40-120 in the upper part; cells near to square. Pyrenoids 1(-2-3) per cell. Holdfast small, inconspicuous, disc-like. Growing on stones, in rocky pools, on muddy bottom with sand, stones and shells, in the middle and low intertidal zones to subtidal (20 m), in sheltered and moderately exposed shores.

Worldwide, arctic to tropical and temperate latitudes in south hemisphere.