Description :

• Perennial, grass-like herbs, completely submerged; forming large colonies in saline or fresh water; with branches up to ± 0.75 m long
• Roots simple, 1 or 2 per node, densely covered with very long roothairs
• Rhizomes creeping, branched, thin; internodes angled
• Stems thin, branching freely
• Leaves alternate or upper ones opposite, spreading; lamina linear to setaceous, up to 100 mm long and 1 mm broad; stipular sheaths attached to base of lamina, wide, folded, membranous, obtuse at apex, amplexicaul at base
• Inflorescences at first enclosed in swollen sheaths of apical leaves, consisting of 2 opposite flowers inserted at different heights, and therefore spicate, but appearing subumbellate in fruit because of stipitate drupes; peduncle remaining short in one species, accrescent in the other, becoming long and spirally coiled
• Flowers bisexual, small, naked, protandrous, water-pollinated
• Stamens 2, opposite; separated thecae divergent, with their short filiform connectives attached to short swollen columnar filament; pollen luniform, buoyant
• Gynoecium of usually 4, occasionally more, free carpels, sessile at first, becoming long-stipitate in fruit; carpels each with a solitary, pendulous, campylotropous ovule; stigma sessile, peltate
• Fruit a drupelet or nutlet, pyriform, often oblique, beaked, sometimes verruculose, on a stipe 10-30 mm long
• Seed hard with brown testa; endosperm 0
• x = 10 (8, 9, 12) (aneuploids, polyploidy)

Nomenclature:

• Ruppia L.
  • Non provided for this genus - See family references

Distribution & Notes:

• Global : Species 1 or 2 or ± 7, depending on interpretation
• Southern Africa : Presently 2 species are recognised but they are perhaps only distinguished by ecological modifications