Represented, with us, by a single species.
L. Hornwort. C. demer'sum, L. An aquatic herb, with whorled finely dissected leaves, and minute axillary sessile monoecious flowers, without calyx or corolla, but with an 8-12-cleft involucre. Staminate flowers of 12-24 stamens with large sessile anthers. Pistillate flowers of a single 1-celled ovary, forming an achene, beaked with the slender style. Embryo with 4 cotyledons. - Under water in ponds and slow streams.
Ovules and seeds naked (not enclosed in a pericarp), and fertilized by the direct application of the pollen. Represented in Canada by a single Order.