Habitat: Hard surfaces; shallow calm coves and harbors; common in fouling communities. The species grows quickly and is often found in nutrient-rich areas, including polluted or recently disturbed habitats with low herbivory. Distribution: Florida, Gulf of Mexico, Caribbean. Natural History Notes: U. lactuca was recently shown to exhibit antitumor and immunostimulating properties. It is considered to be medium quality forage for goats, can be used as a mineral supplement for poultry. Humans can eat it too. Depth: Intertidal to 2m Intremareal hasta 2 m Characteristics: From Caribbean Reef Plants: Thallus thin, sheet-like, as solitary blades or in tufts, normally 10-25cm high, bright green. Blades ruffled or flat, two cells thick; shape variable; margins smooth to undulating, rounded, often lobed. Cells round, square or irregularly polyhedral, 8-12 micron diameter, 12-14 microns long, somewhat longitudinally aligned in pairs or short rows; pyrenoids one per cell, rarely two or three. Stalk inconspicuous or absent. Rhizoidal cells short, basal.