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)

Classification Notes:

• This genus has had a confused taxonomic history both at specific and family levels; often included under the Potamogetonaceae (Phillips 1951; Jacobs & Brock 1982, Cook 1990, Brummitt 1992)

Nomenclature:

• Ruppiaceae
  • Linnaeus: 126 (1753)
  • Bennett: 49 (1897) under Naiadaceae
  • Obermeyer: 70 (1966) (the basis of this account)
  • Jacobs & Brock: 325 (1982)
  • Dahlgren et al.: 312 (1985)
  • Cook: 202 (1990)
  • Brummitt: 743 (1992)

Distribution & Notes:

• Southern Africa: Monogeneric family, cosmopolitan, mainly in temperate regions; species either ± 7, or 1 or 2 polymorphic ones

References:

• BENNETT, A. 1897. Naiadaceae. Flora capensis 7
• BRUMMITT, R.K. 1992. Potamogetonaceae. Vascular plant families and genera. Royal Botanic Gardens, Kew
• COOK, C.D.K. 1990. Aquatic plant book. SPB Academic Publishing, The Hague
• DAHLGREN, R.M.T., CLIFFORD, H.T. & YEO, P.F. 1985. The families of the monocotyledons. Springer-Verlag, Berlin
• JACOBS, S.W.L. & BROCK, M.A. 1982. A revision of the genus Ruppia (Potamogetonaceae) in Australia. Aquatic Botany 14
• LINNAEUS, C. 1753. Species plantarum. Laurentius Salvius, Stockholm
• OBERMEYER, A.A. 1966. Ruppiaceae. Flora of southern Africa 1
• PHILLIPS, E.P. 1951. The genera of South African flowering plants, edn 2. Memoirs of the Botanical Survey of South Africa No. 25

Resources:

• Ruppiaceae genus: Ruppia