Ceratophyllum

Ceratophyllum
Ceratophyllum submersum
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Order:	Ceratophyllales
Family:	Ceratophyllaceae
Genus:	Ceratophyllum L.
Species
See text
Synonyms[1]
Hydroceratophyllon Ség. Dichotophyllum Moench Revatophyllum Röhl. Fassettia Mavrodiev

Ceratophyllum is a cosmopolitan genus of flowering plants including four accepted living species in 2016,^[2] commonly found in ponds, marshes, and quiet streams in tropical and in temperate regions. It is the only extant genus in the family Ceratophyllaceae,^[3] itself the only extant family in the order Ceratophyllales.^[4] They are usually called coontails or hornworts, although hornwort is also used for unrelated plants of the division Anthocerotophyta.

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. Roots are completely absent and are missing even in the embryonic stage,^[5] but sometimes they develop modified leaves with a rootlike appearance, which anchor the plant to the bottom. Also stomata are missing.^[6] 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, which sink to the bottom and give the impression that the plant has been killed by the frost; but come spring, these will grow back into the long stems, slowly filling up the pond.^{[7][8][9][10]}