Stems: Stems absent. Roots 1 per thallus, to 3/5 inch, tip mostly rounded; sheath not winged at base.
Leaves: Leaves not clearly differentiated. Thallus 1 or in clusters of 2-5 or more, usually not reddish on lower surfaces, or if reddish, much less so than on upper surfaces, nearly round to elliptic or obovate, 1/12 to 1/6 inch long, 2--4 x 1/16 to 1/8 inch wide, lower surface slightly convex, upper surface convex or sometimes with an indistinct papilla, veins 3(-5), obscure, greatest distance between lateral veins near or proximal to middle of thallus.
Flowers: Flowers seldom observed, unisexual, 1(-2) per thallus; sepals absent, petals absent; stamens 1-2; pistil 1.
Fruits: Utricles; seeds 1-3, with 8-15 distinct ribs, remaining in fruit wall after ripening.
Comments: Lemna, a Greek name of a water plant.