Description:

• Marine perennials, monoecious or dioecious, with a much-branched creeping rhizome; rhizomes bearing at nodes an abbreviated shoot and a pair of leaves, each surrounded by a basal scale; roots simple, 1 or rarely 2 from a node, densely covered with long root hairs
• Leaves in pairs, petiolate, linear, lanceolate, oblong or ovate, entire or serrulate, glabrous or pubescent; midrib distinct, with a prominent lateral marginal nerve connected to midrib by many oblique secondary nerves
• Flowers unisexual, usually solitary in axil of a secondary shoot, rarely 1 or 2 male and a female flower together in a spathe; spathe of 2 free, membranous bracts
• Male flowers shortly pedicelled, with 3 perianth segments; stamens 3, anthers sessile, 2-4-celled, extrorse; pollen adhering to form threads; pollination hydrophilous
• Female flower sessile; ovary ovoid, beaked, bearing 3 reduced perianth segments near apex; styles 2-6, linear
• Fruit ovoid, rostrate, thin-walled
• Seeds few to many, small, globose. x = 9

Nomenclature:

• Halophila Thouars
  • Thouars: 2 (1808)
  • Obermeyer: 100 (1966)
  • Den Hartog: 238 (1970)
  • Cook: 99 (1990)

Distribution & Notes:

• Global: Species 9, tropical to warm seas of the world
• Southern Africa: Species 1: Halophila ovalis (R.Br.) Hook.f., coastal waters of KwaZulu-Natal as far south as Knysna (Western Cape)