Description: Annual erect or prostrate herbs of aquatic or marshy habitats.
Leaves opposite and decussate, sessile, linear to lanceolate, cordate to auriculate at the base.
Inflorescences sessile or pedunculate axillary cymes. Flowers actinomorphic, 4- or rarely 5-merous, heterostylous. Hypanthium campanulate to urceolate, 8-veined. Calyx appendages thick, shorter than or equal to the lobes, or absent. Petals usually small, purple to white. Stamens variable in length. Ovary incompletely septate, mostly 2–4-locular; style variable in length.
Fruit membranous, splitting irregularly; seeds numerous, obovoid.
Distribution and occurrence: World: c. 25 species, tropical to temperate regions. Australia: 4 species (1 species endemic, 1 sp naturalized), all States.
Text by J. Highet & Peter G. Wilson
|One species in NSW: Ammannia multiflora|