Damasonium
Encyclopedia
Damasonium is a genus of three to five species of flowering plant
s in the family Alismataceae
, commonly known as starfruit and (older name) thrumwort. The genus has a subcosmopolitan
but very patchy distribution.
They are aquatic
perennial
herbaceous plant
s growing in shallow water or mud beside ponds. The leaves
are all basal, floating, or aerial in plants on pond margins. The flowers are hermaphrodite
, in one to many whorls
, in umbel
s, raceme
s or panicle
s; they have six stamens, and six to nine carpels arranged in a whorl, connate at the base, each with two to many ventral ovules; The styles are terminal. The fruit
is a whorl of follicles; the follicles are laterally compressed, stellately radiating, with a more or less elongated apical beak.
Species
it went into decline along with the village pond. It once grew in many English counties from Sussex north to Shropshire, but by 1900 was reduced to two ponds in Buckinghamshire and one in Surrey. It is gradually starting to make a come back due to intense conservation efforts.
It seems to need open, well-lit shallow water to grow in and regularly churned up mud for its seeds to germinate.
It is very variable in form according to the depth of the water it is growing in. Dwarf plants with aerial leaves occur growing sub-terrestrially on mud. The number of ovules vary. Usually there are two in each carpel, but carpels with four to many occur over the range. Multi-ovulate forms from southwestern Europe and Sicily were originally described as D. polyspermum.
The shape of the follicles depends on the number of seeds; the beak (empty upper part) of the carpel is elongated in two-seeded plants, whereas in many-seeded plants the seeds occupy more of the follicle and the beak is relatively shorter and less well defined.
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
s in the family Alismataceae
Alismataceae
The water-plantains are a family of flowering plants, comprising 11 genera and between 85-95 species. The family has a cosmopolitan distribution, with the greatest number of species in temperate regions of the Northern Hemisphere...
, commonly known as starfruit and (older name) thrumwort. The genus has a subcosmopolitan
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
but very patchy distribution.
They are aquatic
Aquatic plant
Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...
perennial
Perennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...
herbaceous plant
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
s growing in shallow water or mud beside ponds. The leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
are all basal, floating, or aerial in plants on pond margins. The flowers are hermaphrodite
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
, in one to many whorls
Whorl (botany)
In botany, a whorl is an arrangement of sepals, petals, leaves, or branches in which all the parts are attached at the same point and surround or wrap around the stem.There are four whorls in a general flower...
, in umbel
Umbel
An umbel is an inflorescence which consists of a number of short flower stalks which are equal in length and spread from a common point, somewhat like umbrella ribs....
s, raceme
Raceme
A raceme is a type of inflorescence that is unbranched and indeterminate and bears pedicellate flowers — flowers having short floral stalks called pedicels — along the axis. In botany, axis means a shoot, in this case one bearing the flowers. In a raceme, the oldest flowers are borne...
s or panicle
Panicle
A panicle is a compound raceme, a loose, much-branched indeterminate inflorescence with pedicellate flowers attached along the secondary branches; in other words, a branched cluster of flowers in which the branches are racemes....
s; they have six stamens, and six to nine carpels arranged in a whorl, connate at the base, each with two to many ventral ovules; The styles are terminal. The fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
is a whorl of follicles; the follicles are laterally compressed, stellately radiating, with a more or less elongated apical beak.
Species
- Damasonium alismaDamasonium alismaDamasonium alisma is a species of flowering marsh plant known by the common name of starfruit. It is native to the British Isles and was commonly found in south and central England. Numbers have declined as a result of the loss of pond habitats. It was not recorded in the wild in 2006 and is...
Mill. (syn. D. stellatum Thuill.; D. polyspermum Cosson; D. constrictum Juz.). Western, southern and southeastern EuropeEuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, western AsiaAsiaAsia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, northern AfricaAfricaAfrica is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. - Damasonium californicumDamasonium californicumDamasonium californicum is a species of perennial wildflower in the water plantain family which is known by the common name California damasonium. This is a plant of wet environments in the western United States from California to Idaho. It is a resident of ponds, riversides, and vernal pools...
Torr. ex Benth. Western United StatesUnited StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
. - Damasonium minus (R. Br.) Buchenau (syn. D. australe Salisb.). Southeastern AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.
Ecology
D. alisma grows in acidic ponds. In Great BritainGreat Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
it went into decline along with the village pond. It once grew in many English counties from Sussex north to Shropshire, but by 1900 was reduced to two ponds in Buckinghamshire and one in Surrey. It is gradually starting to make a come back due to intense conservation efforts.
It seems to need open, well-lit shallow water to grow in and regularly churned up mud for its seeds to germinate.
It is very variable in form according to the depth of the water it is growing in. Dwarf plants with aerial leaves occur growing sub-terrestrially on mud. The number of ovules vary. Usually there are two in each carpel, but carpels with four to many occur over the range. Multi-ovulate forms from southwestern Europe and Sicily were originally described as D. polyspermum.
The shape of the follicles depends on the number of seeds; the beak (empty upper part) of the carpel is elongated in two-seeded plants, whereas in many-seeded plants the seeds occupy more of the follicle and the beak is relatively shorter and less well defined.