Ulva flexuosa

Thallus simple, slender, soft, flaccid, tubular, inflated and flexuose above, gregarious, or in tufts, light- to dark-green, 5-12(-60) cm long, 1-7(-10) mm broad. Thallus occasionally sparsely branched near the base into 2-3 similar branches, with or without proliferations. Branches gradually tapering downward, hollow, above slightly compressed, inflated, flexuous. Tips blunt, slightly swollen. Cells in surface view in regular longitudinal series; in young branches often in transverse series, quadrangular, rectangular, irregularly rounded-polygonal, 15-18×10-20(-25) mm, basal cells to 50 mm long. In transverse section, cells oval to roundish, 18-25 mm high and 10-15(-25) mm broad, sometimes with thickened lamellar inner membrane wall (in basal part of thallus). Chloroplast parietal with 1-6(-8) (mostly 2-3) pyrenoids per cell. Rhizoids fusing to form lower stalk and basal pad. Growing on stones, in upper intertidal.

Temperate north hemisphere to temperate latitudes of south hemisphere.