Description:

• Small, creeping, coastal, submerged annuals
• Roots 4-7 from a node, simple, long, densely covered with long root-hairs
• Rhizome branched, slender, with a deciduous, lanceolate, amplexicaul scale from each node
• Stems simple, erect, up to 150 mm long, filiform
• Leaves usually aggregated above, filiform-setaceous, up to 50 mm long; sheaths folded, membranous, about 5 mm long, forming a forked appendage above, 2-3 mm long, becoming frayed with age
• Flowers in clusters
• Male flowers solitary, on a pedicel which elongates up to 4-5 mm during anthesis so that anther is just exserted, often with 3, as yet undeveloped, female flowers beside them; perianth a small 3-toothed cup, with the 1-thecous anther sessile or subsessile; pollen globose
• Female flowers usually 3 together; (1-)3-carpellate; carpels stipitate, each enfolded in a membranous bract, narrow-ovoid, unilocular, with long style and saucer-shaped apical stigma
• Fruit a stipitate, cylindrical, slightly oblique, smooth drupelet crowned with persistent, pin-like style and stigma base

Nomenclature:

• Althenia F.Petit
  • Petit: 451 (1829)
  • Obermeyer: 79 (1966)
  • Cook: 222 (1990)

Distribution & Notes:

• Global: Species 3, or 1 polymorphic species: Althenia filiformis F.Petit, Mediterranean coast, Atlantic coast of Morocco, Portugal, Spain, France, Asia Minor, central Siberia and southern Africa
• Southern Africa: Coastal waters of Namibia and South Africa as far as Port Elizabeth (Eastern Cape)