Plants , submersed perennials. Stems suspended or anchored by branches buried in substrate; branches 0-3 per node. Leaves 3-11 per whorl, cauline; petiole inconspicuous. Leaf blade simple or forked into linear-filiform, denticulate segments. Inflorescences extra-axillary, alternating with leaves. Flowers: bracts basally connate, foliaceous; pedicel less than 1 mm or essentially absent. Staminate flowers: anther 2-locular, connective projecting as apical appendage. Pistillate flowers: ovary tapering to persistent, spinelike style; ovule pendulous. Achene ellipsoid, moderately compressed, surface smooth or tuberculate, basal or marginal spines (or both) present or absent, terminal spine present, marginal wing present or absent. x = 12, 19, 20. Plumule features used in the key below are observable through dissection of softened (soaked) seeds removed from achenes.

PLANTS: Perennial herbs, free-floating submerged, rootless; monoecious. STEMS: flexuous or brittle with irregular branching. LEAVES: whorled, simple, linear or dichotomously divided into linear filiform segments, with 2 sub-marginal rows of persistent spine-like denticles; segment apices tipped by multicellular appendages. INFLORESCENCE: sessile or subsessile solitary flowers at nodes, subtended by a whorl of connate foliaceous bracts. FLOWERS: hypogynous, greatly reduced; pedicels less than 1 nun 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: an achene. 2n = 24 NOTES: (Greek: keras = horn + phyllon = leaf, forked leaves resembling antlers). REFERENCES: Ricketson, Jon. 1995. Ceratophyllaceae. J. Ariz. – Nev. Acad. Sci. 29(1): 17.