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A cosmopolitan family of two species in one genus, the single Australian species (Ceratophyllum demersum) is sometimes found submerged in still, permanent, fresh water lakes and swamps in all mainland States.

Characteristic features of the family Ceratophyllaceae in Australia include:

  • a peculiar, rough, brittle, rootless, submerged waterplant with whorled, much-divided leaves
  • flowers tiny, unisexual, axillary, pollinated underwater
  • fruit black, bony, indehiscent, with 1-several spines


Perennial aquatic herbs, free-floating at or below the water surface. Perennating by turions (a short, condensed shoot, filled with starch). Internal secretions not obvious. Plants glabrous. Leaves in whorls of 7 or more, cauline. Stipules absent. Lamina simple, symmetric, dorsiventral, bipinnatifid, tripinnatifid, etc; segments filiform, acicular, subulate or linear; base attenuate; margins spiny, ±flat; venation not obvious; surfaces not punctate; herbaceous or leathery. Male and female flowers occurring on the same plant. Inflorescences axillary, consisting of solitary flowers. Bracteoles absent. Pollination by water. Flowers odourless. Floral disc absent; nectaries absent. Perianth regular, of 1 whorl only or all whorls ±similar, with 815 sepaloid segments, fused shortly at base, with the most prominent perianth segments green, without contrasting markings; inner perianth parts herbaceous. Fertile stamens 810 (25), free of the perianth segments, free of the ovary and style, distinct from each other, all ±equal. Staminal filaments distinctly flattened and with embedded anther-sacs. Anthers not versatile, opening inwards by longitudinal slits, 2-celled, with apical appendages. Ovary superior and sessile. Carpel 1. Style terminal, single and unbranched. Ovules 1 per carpel, stalked; placentation apical. Fruit a dry, indehiscent achene or a nut; the perianth on the maturing fruit dry and persistent. Disseminule macro-surface with spines; micro-surface ±tuberculate, black, dull. Seeds 1 per fruit. Aril present. Cotyledons 2. Embryo straight.
(Note: this description has been generated from the coded data compiled for the key. Any errors in the key data will be reflected in the descriptions.)

A treatment of the family Ceratophyllaceae has not yet been published in the Flora of Australia. It will appear in Volume 2.

Australian genera of Ceratophyllaceae (as recognised for the Flora of Australia)


Ceratophyllum demersum (flowers and fruit)
Photo: S.Jacobs S.Jacobs 

Ceratophyllum demersum (fruits)
Photo: S.Jacobs S.Jacobs 

Ceratophyllum demersum (habit)
Photo: M.Fagg ANBG