''Hygrophila'', commonly known as swampweeds, is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of ...

s in the acanthus family,

Acanthaceae Acanthaceae is a family (the acanthus 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 ...

. There are about 80''Hygrophila''.
Flora of Pakistan. to 100''Hygrophila''.
Flora of China.Hài, Đ. V. and D. Đ. Huyến. (2012)
New record of species ''Hygrophila episcopalis'' R. Ben. (R. Ben.) (Acanthaceae) for the flora of Vietnam.
''Journal of Biology'' 34(2), 187-89. species, of which many are

aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments ( saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

s. The genus is distributed across the tropical and subtropical world. 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.

Description

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

pinnate Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, an ...

ly divided basal leaves with either filiform (feather-like) or linear segments, and undivided leaves higher on the stem. The

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

s 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

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...

s. Two may be staminodal, lacking

pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametop ...

. 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.

Ecology and uses

A number of species are cultivated for the aquarium trade, including '' H. difformis'' (water wisteria) and '' Hygrophila polysperma'' (Indian swampweed). Many members of the genus are troublesome weeds in irrigation and drainage ditches as well as rice fields. Several have become established outside of their native ranges, largely due to the aquarium trade, such as ''H. polysperma'' in the southern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

Gallery

File:Hygrophila serpyllum in Hyderabad, AP W IMG 4437.jpg, '' Hygrophila serpyllum'' File:Hygrophila difformis.jpg, '' Hygrophila difformis'' File:Hygrophila schulli Acanthaceae.jpg, '' Hygrophila schulli'' File:Hygrophila pogonocalyx.jpg, '' Hygrophila pogonocalyx''

References

External links

*
''Hygrophila'' subordinate taxa.
Tropicos.
''Hygrophila''.
The Plant List. {{Taxonbar, from=Q241151 Acanthaceae genera