Ceratophyllum L.

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.

In stagnant pools, small slow streams, shallow parts of lakes and ditches, in ponds, often gregarious. The specimens are frequently rough by incrustations of lime. They 'collect' mud on their surface and contribute to the clearing of water as do Hydrilla, Blyxa, &c. The stems die at their distal end and grow at the top. They propagate easily vegetatively but remain often sterile; near Batavia they are locally rather frequently found flowering in shallow water. The leaves are slack though in C. demersum slightly stiffer than in C. submersum. On extracting material from the water the leaves join brush-like.