Ceratophyllum demersum L.

Hornwort

Sp. Pl. 992 (1753) APNI

Taxonomic status:Accepted

Occurrence status:Present

Establishment means:Native

Threat status:Victoria: data deficient (k)

Plants unattached or rarely loosely attached to sediment, rough to touch, stiff and brittle. Stems usually 30–60 cm long and less than 1 mm diam. Leaves c. 7–12 per whorl, 1–4 cm long, dichotomously forked 1–4 times; ultimate segments narrow, more or less cylindric, tapered, with small teeth, apices usually truncate and toothed at each side. Flowers small, greenish and inconspicuous, involucral lobes 1.5–2 mm long, variously toothed at apex, often with long apical projection. Fruit c. 4.5 mm long (excluding spine), black, with 3 soft spines longer than fruit, 1 terminal (a persistent style) and 2 laterally almost basal and spreading (one or both basal spines may develop only partially). Flowers Jan.–Feb.

GipP, MuF, MuM, MSB, NIS, RobP, Strz, VRiv, VVP. Also WA, NT, Qld, SA, NSW. Europe, Asia, Africa, Malaysian region, New Guinea, North America, introduced into New Zealand. Scattered through Victoria, often forming dense growths in usually fresh, still to slow-flowing waters, a few metres deep or less.

Extensive growths can choke drainage channels and hydroelectricity systems.

Pollination is achieved by stamens becoming detached from the plant and rising to the surface. The pollen is then released and sinks, some landing on the female flowers.

Myriophyllum (Haloragaceae) is superficially similar to Ceratophyllum, but the leaves of that genus are divided pinnately rather than dichotomously. Cabomba caroliniana (Cabombaceae) has dichotomously divided leaves but the ultimate leaf-segments are smooth rather than toothed and the leaves 3 or more times divided at base.

Source: Entwisle, T.J. (1996). Ceratophyllaceae. In: Walsh, N.G.; Entwisle, T.J. (eds), Flora of Victoria Vol. 3, Dicotyledons Winteraceae to Myrtaceae. Inkata Press, Melbourne.
Hero image
Distribution map
life Life
kingdom Plantae
phylum Tracheophyta
superorder Ceratophyllanae
Higher taxa

Victoria

Source: AVH (2014). Australia's Virtual Herbarium, Council of Heads of Australasian Herbaria, <http://avh.chah.org.au>. Find Ceratophyllum demersum in AVH ; Victorian Biodiversity Atlas, © The State of Victoria, Department of Environment and Primary Industries (published Dec. 2014) Find Ceratophyllum demersum in Victorian Biodiversity Atlas
  Bioregion Occurrence status Establishment means
Murray Mallee present native
Victorian Volcanic Plain present native
Victorian Riverina present native
Murray Scroll Belt present native
Robinvale Plains present native
Murray Fans present native
Gippsland Plain present native
Northern Inland Slopes present native
Strzelecki Ranges present native

State distribution

Distribution map
State
Western Australia
Northern Territory
South Australia
Queensland
New South Wales
Victoria
Tasmania