Plant: perennial, free-floating, submerged herb, rootless; monoecious; STEM flexuous or brittle with irregular branching; tips often with shortened internodes causing dense apical clustering of leaf whorls, these 15-60 mm in diameter when mature Leaves: deep green, simple, or dichotomously divided, forked once, twice, or rarely three times, into 2-4(-6) ultimate segments, that are not inflated; denticles strongly exserted, coarse-textured Inflorescence: sessile or subsessile solitary flowers at nodes, subtended by a whorl of connate foliaceous bracts Flowers: hypognous, greatly reduced; pedicels less than 1 mm long; perianth absent; STAMINATE FLOWERS with 3-many subsessile stamens; PISTILLATE FLOWERS 1-carpelled; style terminal, persistent, elongate-spinescent or short subulate, the apex acute Fruit: moderately compressed achene, the body 3.5-6.0 mm long, 2.0-4.0 mm wide, 1.0-2.5 mm thick, dark green or reddish-brown at maturity, the surface smooth to tuberculate, the faces spineless; terminal stylar spine straight, 0.5-14.0 mm long, persistent; basal spines 2, straight or curved, 0.5-12 mm long, their bases occasionally inconspicuously webbed Misc: Ponds, lakes, slow-moving streams, and river backwaters; 50-2750 m (100-9000 ft); fl Apr-Sep (fr Jun-Oct) REFERENCES: Ricketson, Jon. 1995. Ceratophyllaceae. J. Ariz. – Nev. Acad. Sci. 29(1): 17.