Description :

• Marine perennials, monoecious, completely submerged; with creeping, much-branched, compressed, orange-brown rhizomes; with several simple roots with long roothairs at nodes
• Stems , if present, floriferous, annual
• Leaves alternate, distichous, grass-like, parallel-veined, sheathing at base; sheath tubular or convolute, with a small biauriculate ligule; lamina linear, striate, apex rounded, 2-lobed or emarginate, axillary scales 4 or 2
• Inflorescences forming erect annual sympodial branches, each terminating in a 'fertile' leaf, enclosing in its sheath a unilateral spadix on which male and female flowers are arranged alternately in 2 rows, with or without marginal bract-like infolded lobes or 'retinacula' (interpreted by some botanists as a reduced perianth)
• Male flower a solitary, sessile, unilocular, dorsifixed anther; pollen filiform, with same density as seawater, captured by stigmas
• Female flower consisting of a superior, unilocular, 1-ovuled ovary terminating in a short style and 2 long stigmatic branches, protogynous (stigmas protruding from sheath during anthesis); ovule pendulous, orthotropous, bitegmic
• Fruit an indehiscent, or irregularly dehiscent nut, graniform, smooth or longitudinally striped or ribbed
• Seed : endosperm 0
• x = 6 (polyploidy)

Nomenclature:

• Zostera L.
  • Linnaeus: 968 (1753)
  • Bennett: 50 (1897)
  • Obermeyer: 58 (1966)
  • Den Hartog: 42 (1970)
  • Cook: 224 (1990)

Distribution & Notes:

• Global : Species 12, mostly marine but sometimes in brackish water, cosmopolitan in warm and temperate areas
• Southern Africa : Species 1: Zostera capensis Setch., widely distributed from Saldanha Bay on the west coast, around the Cape, along the east coast, occurring in marine pools and lagoons
  • Extending as far as Kenya and Madagascar