Ulva compressa

Thallus soft, gregarious, forming dense tufts or turfs, tubular, compressed, 1-5(-40) cm high. Branching sparse at the basal portion. Branches similar to main axis: cylindric and narrow below, expanding above (1.4-3.0 cm broad) and becoming compressed (with margins hollow), sometimes constricted. Cells in surface view at lower portion of thallus rounded rectangular, subquadrangular, elongated in narrow portions, 10-12.5(-28)x10- 35(-70) mm; pyrenoids 1(-2). In the upper portion of thallus, cells as above and polygonal, 10-17.5(-25)x10-20 mm; pyrenoids 2-3. Randomly cells arranged in longitudinal and transverse rows. In transverse section, cells oval, 27.5 mm high, 12.5 mm wide. Attachment by holdfast composed of fused rhizoidal cells forming stalk and basal pad. Growing, in the middle, low intertidal zones to subtidal, on hard substrate.

Temperate to tropical latitudes of Atlantic, Indian and Pacific Oceans.