Hygrophila | |
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Hygrophila polysperma in an aquarium | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Asterids |
Order: | Lamiales |
Family: | Acanthaceae |
Subfamily: | Acanthoideae |
Tribe: | Ruellieae |
Genus: | Hygrophila R.Br. (1810) |
Species [1] | |
77; see text | |
Synonyms [1] | |
|
Hygrophila, commonly known as swampweeds, [2] [3] is a genus of flowering plants in the acanthus family, Acanthaceae. There are about 80 [4] to 100 [5] [6] species, of which many are aquatic plants. The genus is distributed across the tropical and subtropical world. [4] [5] It is one of only two genera in its family that contains aquatic plants, the other being Justicia . The genus is treated in the tribe Hygrophileae, which is noted as being in need of revision at the genus level, meaning the current taxonomic boundaries of Hygrophila are likely to change in the future. [7]
The leaves are either homomorphic, all with one form, or heteromorphic, with different forms on one plant. Homomorphic leaves are always simple and entire. Plants with heteromorphic leaves generally have pinnately divided basal leaves with either filiform (feather-like) or linear segments, and undivided leaves higher on the stem. [7]
The flowers have white to purple corollas with either 5 equal lobes or 2 lips. A lipped corolla has an erect, concave upper lip with two lobes, and a lower lip with 3 lobes. The flower has four stamens. Two may be staminodal, lacking pollen. The individual filaments of the stamens are united into pairs by a membrane. There is an inconspicuous nectar disc. Each flower yields at least 6 seeds. [7]
A number of Hygrophila species and cultivars are popular within the aquascaping and aquarium hobbies, including H. angustifolia, H. corymbosa, H. lancea 'Araguaia', [8] H. pinnatifida, H. difformis 'Water Wisteria', H. odora, H. polysperma 'Indian swampweed' and H. siamensis. Additionally, there are some striking newer forms on the market, such as the vivid hybrids of Hygrophilapolysperma, 'Sunset' [9] and 'Rosanervig'. [10]
Many members of the genus are troublesome weeds if they become established within irrigation systems, drains or drainage ditches, as well as in rice fields. Several have become established outside of their native ranges, either due to accidentally-discarded cuttings or deliberate release, such as H. polysperma in the southern United States. [7]
77 species are accepted: [1]
Acanthaceae is a family of dicotyledonous flowering plants containing almost 250 genera and about 2500 species. Most are tropical herbs, shrubs, or twining vines; some are epiphytes. Only a few species are distributed in temperate regions. The four main centres of distribution are Indonesia and Malaysia, Africa, Brazil, and Central America. Representatives of the family can be found in nearly every habitat, including dense or open forests, scrublands, wet fields and valleys, sea coast and marine areas, swamps, and mangrove forests.
Strobilanthes is a genus of about 350 species of flowering plants in the family Acanthaceae, mostly native to tropical Asia and Madagascar, but with a few species extending north into temperate regions of Asia. Many species are cultivated for their two-lipped, hooded flowers in shades of blue, pink, white and purple. Most are frost-tender and require protection in frost-prone areas. The genus is most famed for its many species which bloom on long cycles of several years, such as Strobilanthes wightii which blooms every thirteen years.
Justicia is a genus of flowering plants in the family Acanthaceae. It is the largest genus within the family, with over 900 accepted species. They are native to tropical to warm temperate regions of the Americas, India, and Africa. The genus serves as host to many butterfly species, such as Anartia fatima. Common names include water-willow and shrimp plant, the latter from the inflorescences, which resemble a shrimp in some species. The generic name honours Scottish horticulturist James Justice (1698–1763). They are closely related to Pachystachys.
Ruellia is a genus of flowering plants commonly known as ruellias or wild petunias. They are not closely related to petunias (Petunia) although both genera belong to the same euasterid clade. The genus was named in honor of Jean Ruelle (1474–1537), herbalist and physician to Francis I of France and translator of several works of Dioscorides.
Dicliptera is a genus of flowering plants in the bear's breeches family, Acanthaceae. It includes 223 species native to the tropics and subtropics worldwide. Well-known synonyms include Peristrophe and Dactylostegium.
Lepidagathis is a genus of flowering plants in the family Acanthaceae. It includes 151 species native to the tropics of the Americas, sub-Saharan Africa, south and southeast Asia, southern China, Malesia, and New Guinea.
Hypoestes is a flowering plant genus of about 150 species. They are widely distributed throughout the tropical and subtropical lands around the Indian Ocean, and some adjacent regions.
The genus Asystasia belongs to the family Acanthaceae and comprises 59 species found in the tropics of Africa, Asia, Australia, and New Guinea. It includes the weedy species Asystasia gangetica.
Acanthopale is a plant genus of shrubs or subshrubs in the Acanthaceae plant family. The genus name is based on the classic Greek words for thorn ákantha and stake palum. Some species in the genus are cultivated as ornamental plants.
Anisotes is a genus of Afrotropical plants in the family Acanthaceae. The genus is morphologically similar to Metarungia, from which it differs mainly in the dehiscence of the fruit capsule, and the nature of the placenta. Placentas remain attached to the inner surface of fruit capsules in Anisotes.
Blepharis is a genus of plant in family Acanthaceae. It contains around 128 species found in seasonally dry to arid habitats from Africa through Arabia to Southeast Asia. In section Acanthodium, there are 13–15 species that use the C4 carbon fixation pathway. Phylogenetic analysis suggests that this pathway evolved up to three times independently in the genus over the last five million years.
Pseuderanthemum is a genus of plants in family Acanthaceae with a pantropical distribution.
Crossandra is a genus of plants in the family Acanthaceae, comprising 54 species that occur in Africa, Madagascar, Arabia and the Indian subcontinent. Some species, especially Crossandra infundibuliformis, are cultivated for their brightly colored flowers.
Dyschoriste is a genus of flowering plants in the family Acanthaceae. It includes 98 species native to the tropics and subtropics of the Americas, sub-Saharan Africa, and southern Asia. Members of the genus are commonly known as snakeherb.
Ecbolium is a genus of flowering plants in the family Acanthaceae. It includes 26 species native to southern and eastern Africa, the Arabian Peninsula, Indian subcontinent, and Myanmar.
Phlogacanthus is a genus of flowering plants in the family Acanthaceae and tribe Andrographideae. Its distribution includes India through to Indo-China, southern China, Java, and Sulawesi.
Rungia is a genus of flowering plants belonging to the family Acanthaceae.
Ptyssiglottis is a genus of flowering plants belonging to the family Acanthaceae. It includes 38 species native to tropical Asia and Papuasia, ranging from Sri Lanka to Indochina, Malesia, New Guinea, and the Bismarck Archipelago.