Ulva intestinalis

Thalli simple or sparse branching near base, green to yellowish-green, 1-30(-60-100) cm high, 0.5-1.0(-10) cm wide, gregarious or loose, composed of several cylindrical, hollow, tubular or flattened blades, with smooth or wrinkled surface, tapering below to cuneate base. Margins entire or twisted to curly. Cells in surface view 4-6-angular, of irregular shape, with disorder arrangement from base to tip. Basal cells rounded, of equal diameters, larger and darker than above. In transverse section, walls one cell thick, 26-30 μm high with thickened inner mucilage layer. Chloroplast entire, with rough margins. Pyrenoids generally 1, rarely 2 per cell. Attachment by small discoid holdfast. Growing in the upper intertidal zone on rocks, dead coral fragments and dead shells in brackish waters of estuaries.

Arctic to tropical and temperate waters of south hemisphere.