L., Sp. Pl. 963. 1753
Water lettuce, Lechuga de agua
Floating aquatic, nearly acaulescent; caudex sometimes producing stolons with new rosettes of leaves at apex. Leaves forming dense rosette; petioles very short; blades ± obovate, rounded or emarginate at apex, cuneate at base, mostly 5-17 cm long, 2-7 cm wide, thick and spongy, pubescent on both surfaces with short, few-celled trichomes; veins in 5-15 pairs, parallel, prominent beneath. Inflorescences small and inconspicuous, subsessile, borne among leaves; spathe white, constricted at middle, the lateral margins connate to middle; spadix shorter than spathe and adnate to it for two-thirds of its length, with a single naked pistillate flower and 2-8 naked staminate flowers arranged in verticils; stamens 2, connate to form a synandrium; ovary obliquely attached to spadix, 1-celled; ovules numerous with basal placentation. Seeds cylindrical, minute. Croat 8431.
Occasional, at the lake margin, usually in quiet waters. Flowering period unknown.
Throughout the tropics of the world. Probably throughout Panama at lower elevations; known from tropical moist forest on both slopes in the Canal Zone and in Panama and Darién.