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.

The only genus of the family.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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