Ceratophyllum is a cosmopolitan genus of flowering plants commonly found in ponds, marshes, and quiet streams in tropical and in temperate regions. It is the only extant genus in the family Ceratophyllaceae, itself the only extant family in the order Ceratophyllales. They are usually called coontails or hornworts, although hornwort is also used for unrelated plants of the division Anthocerotophyta.

Description

Ceratophyllum grows completely submerged, usually, though not always, floating on the surface of the water. 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, but sometimes they develop modified leaves with a rootlike appearance, which anchor the plant to the bottom. Stomata are not present on any species. 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.

Taxonomy

Ceratophyllum was first described by Carl Linnaeus in 1753 with Ceratophyllum demersum as the type species. The APG IV system placed the family in its own order, the Ceratophyllales, and gives the following cladogram.

References

  • Ceratophyllaceae of Mongolia in FloraGREIF