Description: Thallus is a thin, bright green blade up to 20 cm (8 in) tall with finely ruffled margins. Blades, which are one cell thick, start out as small sacs, then split open as they expand. Cells are small, 4-6 μm diameter. Habitat: This annual grows primarily on seagrass and other substrates in semi-exposed to protected habitats.  Similar taxa: Monostroma, Protomonostroma, Ulvaria.