Ceratophyllum is a cosmopolitan genus of flowering plants including
four accepted species in 2016, commonly found in ponds, marshes,
and quiet streams in tropical and in temperate regions. It is the only
genus in the family Ceratophyllaceae, itself the only family in the
order Ceratophyllales. They are usually called coontails or
hornworts, although hornwort is also used for unrelated plants of the
Ceratophyllum grows completely submerged, usually, though not always,
floating on the surface, and does not tolerate drought. The plant
stems can reach 1–3 m in length. At intervals along nodes of the
stem they produce rings of bright green leaves, which are narrow and
often much-branched. The forked leaves are brittle and stiff to the
touch in some species, softer in others. The plants have no roots at
all, but sometimes they develop modified leaves with a rootlike
appearance, which anchor the plant to the bottom. The flowers are
small and inconspicuous, with the male and female flowers on the same
plant. In ponds it forms thick buds (turions) in the autumn that sink
to the bottom which give the impression that it has been killed by the
frost but come spring these will grow back into the long stems slowly
filling up the pond.
Hornwort plants float in great numbers just under the surface. They
offer excellent protection to fish-spawn, but also to snails that are
infected with Bilharzia. Because of their appearance and their high
oxygen production, they are often used in freshwater aquaria.
3 External links
Ceratophyllum is considered distinctive enough to warrant its own
family, Ceratophyllaceae. It was considered a relative of Nymphaeaceae
and included in
Nymphaeales in the Cronquist system, but recent
research has shown that it is not closely related to
any other extant plant family. Some early molecular phylogenies
suggested it was the sister group to all other angiosperms, but more
recent research suggests that it is the sister group to the eudicots.
APG III system placed the family in its own order, the
APG IV system
APG IV system accepts the phylogeny
The division of the genus into species is not completely settled. More
than 30 species have been described, but many are probably just
variants of these more widely accepted species:
Ceratophyllum demersum L. (rigid hornwort or common hornwort) -
Ceratophyllum echinatum A.Gray (spineless hornwort) - North America
Ceratophyllum muricatum Cham. (prickly hornwort) - widespread in many
places though not all countries
Ceratophyllum platyacanthum Cham. - Scattered locations in Germany,
Hungary, France, Russia, China, Japan, Korea
Ceratophyllum submersum L. (soft hornwort or tropical hornwort) -
Europe, Central Asia, northern Africa, scattered places in tropical
Africa, Turkey, Oman, Florida, Dominican Republic
Ceratophyllum demersum is widespread, with a global
distribution; the others all have more restricted ranges.
^ a b c Angiosperm Phylogeny Group (2009). "An update of the
Angiosperm Phylogeny Group classification for the orders and families
of flowering plants: APG III" (PDF). Botanical Journal of the Linnean
Society. 161 (2): 105–121. doi:10.1111/j.1095-8339.2009.00996.x.
^ a b c d Kew World Checklist of Selected
^ Christenhusz, M. J. M.; Byng, J. W. (2016). "The number of known
plants species in the world and its annual increase". Phytotaxa.
Magnolia Press. 261 (3): 201–217.
^ a b Angiosperm Phylogeny Group (2016). "An update of the Angiosperm
Phylogeny Group classification for the orders and families of
flowering plants: APG IV". Botanical Journal of the Linnean Society.
181 (1): 1–20. doi:10.1111/boj.12385.
^ a b Flora of China: Ceratophyllum
^ a b Flora of North America: Ceratophyllum
^ Blamey, M. & Grey-Wilson, C. (1989). Flora of Britain and
Northern Europe. ISBN 0-340-40170-2
^ Huxley, A., ed. (1992). New RHS Dictionary of Gardening. Macmillan
^ Angiosperm Phylogeny Web: Ceratophyllales
^ Germplasm Resources Information Network: Ceratophyllum
Plant Name Index: Ceratophyllum
^ Flora Europaea: Ceratophyllum
Wikimedia Commons has media related to Ceratophyllum.
Ceratophyllaceae of Mongolia in FloraGREIF