Ceratophyllum | |
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Ceratophyllum submersum | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Order: | Ceratophyllales |
Family: | Ceratophyllaceae |
Genus: | Ceratophyllum L. |
Species | |
See text | |
Synonyms [1] | |
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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]
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 Nymphaeaceae or 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. This notion was supported upon sequencing of the C. demersum genome in 2020. [11] The APG III system placed the family in its own order, the Ceratophyllales. [3] [12] [13] The APG IV system accepts the phylogeny shown below: [4]
The subgeneric division of the genus Ceratophyllum into its appropriately recognized species, subspecies, and varieties is not settled. More than 30 species have been described and published. A narrow interpretation of this work rejects over 24 of these taxa as variants, accepting only 6 species. This narrow interpretation lumps to the point of failing to give these potential species the taxonomic importance of even being named on a subspecific or varietal level. The genus as narrowly defined in this manner contains the following six species: [3] [7] [8] [14] [15] [1]
The Nymphaeales are an order of flowering plants, consisting of three families of aquatic plants, the Hydatellaceae, the Cabombaceae, and the Nymphaeaceae. It is one of the three orders of basal angiosperms, an early-diverging grade of flowering plants. At least 10 morphological characters unite the Nymphaeales. One of the traits is the absence of a vascular cambium, which is required to produce both xylem (wood) and phloem, which therefore are missing. Molecular synapomorphies are also known.
Nymphaeaceae is a family of flowering plants, commonly called water lilies. They live as rhizomatous aquatic herbs in temperate and tropical climates around the world. The family contains five genera with about 70 known species. Water lilies are rooted in soil in bodies of water, with leaves and flowers floating on or rising from the surface. Leaves are round, with a radial notch in Nymphaea and Nuphar, but fully circular in Victoria and Euryale.
Smilacaceae, the greenbriers, is a family of flowering plants. While they were often assigned to a more broadly defined family Liliaceae, most recent botanists have accepted the two as distinct families, diverging around 55 million years ago during the Early Paleogene. One characteristic that distinguishes Smilacaceae from most of the other members of the Liliaceae-like Liliales is that it has true vessels in its conducting tissue. Another is that the veins of the leaves, between major veins, are reticulate (net-shaped), rather than parallel as in most monocots.
Ceratophyllaceae is a cosmopolitan family of flowering plants including one living genus commonly found in ponds, marshes, and quiet streams in tropical and in temperate regions. It is the only extant family in the order Ceratophyllales. Species are commonly called coontails or hornworts, although hornwort is also used for unrelated plants of the division Anthocerotophyta.
The Xyridaceae are a family of flowering plants. This family has been recognized by many taxonomists and is known as the yellow-eyed grass family.
The water-plantains (Alismataceae) are a family of flowering plants, comprising 20 genera and 119 species. The family has a cosmopolitan distribution, with the greatest number of species in temperate regions of the Northern Hemisphere. Most of the species are herbaceous aquatic plants growing in marshes and ponds.
The Calycanthaceae are a small family of flowering plants in the order Laurales. The family contains three genera and only 10 known species, restricted to warm temperate and tropical regions:
Juncaginaceae is a family of flowering plants, recognized by most taxonomists for the past few decades. It is also known as the arrowgrass family. It includes 3 genera with a total of 34 known species.
Trochodendraceae is the only family of flowering plants in the order Trochodendrales. It comprises two extant genera, each with a single species along with up to five additional extinct genera and a number of extinct species. The living species are native to south east Asia. The two living species both have secondary xylem without vessel elements, which is quite rare in angiosperms. As the vessel-free wood suggests primitiveness, these two species have attracted much taxonomic attention.
Chloranthaceae is a family of flowering plants (angiosperms), the only family in the order Chloranthales. It is not closely related to any other family of flowering plants, and is among the early-diverging lineages in the angiosperms. They are woody or weakly woody plants occurring in Southeast Asia, the Pacific, Madagascar, Central and South America, and the West Indies. The family consists of four extant genera, totalling about 77 known species according to Christenhusz and Byng in 2016. Some species are used in traditional medicine. The type genus is Chloranthus. The fossil record of the family, mostly represented by pollen such as Clavatipollenites, extends back to the dawn of the history of flowering plants in the Early Cretaceous, and has been found on all continents.
Euptelea is a genus of two species of flowering plants in the monogeneric family Eupteleaceae. The genus is found from Assam east through China to Japan, and consists of shrubs or small trees:
Myrothamnus is a genus of flowering plants, consisting of two species of small xerophytic shrubs, in the southern parts of tropical Africa and in Madagascar. Myrothamnus is recognized as the only genus in the family Myrothamnaceae.
Pandanaceae is a family of flowering plants native to the tropics and subtropics of the Old World, from West Africa to the Pacific. It contains 982 known species in five genera, of which the type genus, Pandanus, is the most important, with species like Pandanus amaryllifolius and karuka being important sources of food. The family likely originated during the Late Cretaceous.
Scheuchzeria palustris, is a flowering plant in the family Scheuchzeriaceae, in which there is only one species and Scheuchzeria is the only genus. In the APG II system it is placed in the order Alismatales of the monocots.
Haloragaceae is a eudicot flowering plant family in the order Saxifragales, based on the phylogenetic APG system. In the Cronquist system, it was included in the order Haloragales.
Ceratophyllum demersum, commonly known as hornwort, rigid hornwort, coontail, or coon's tail, is a species of flowering plant in the genus Ceratophyllum. It is a submerged, free-floating aquatic plant, with a cosmopolitan distribution, native to all continents except Antarctica. It is a harmful weed introduced in New Zealand. It is also a popular aquarium plant. Its genome has been sequenced to study angiosperm evolution.
Hydrostachys is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of Hydrostachys are aquatic, growing on rocks in fast-moving water. They have tuberous roots, usually pinnately compound leaves, and highly reduced flowers on dense spikes.
Ceratophyllum echinatum, known as prickly hornwort, spiny hornwort, or spiny coontail, is an aquatic, perennial plant found in North America. Its name comes from fruits, which have a warty surface and long spines. Spiny hornwort can be found in ponds and lakes, principally in eastern North America. It is the only species of its genus endemic to North America.
The anthophytes are a grouping of plant taxa bearing flower-like reproductive structures. They were formerly thought to be a clade comprising plants bearing flower-like structures. The group contained the angiosperms - the extant flowering plants, such as roses and grasses - as well as the Gnetales and the extinct Bennettitales.