Description:

• Floating, rootless herbs
• Stems unbranched, horizontal, transparent, just submerged, occasionally branching pseudo-dichotomously, new parts developing apically with older leaf whorls dying off successively; forming turions in winter
• Leaves 6-9 in verticils, connate at base, petiolar part broad, hollow, turgid, apically forming 4-6 subulate, ciliate segments; lamina reniform-rounded, articulate, with long sensitive bristles inside near midrib, causing lobes to close tightly when irritated; sessile, digestive glands present
• Flowers axillary, solitary, emergent; peduncle robust, reflexed in fruit
• Calyx: lobes imbricate, ovate-elliptic
• Petals cohering at first to form cap, white, obovate
• Stamens 5; filaments subulate; anthers didymous
• Ovary sessile, subglobose; placentas 5; styles 5, filiform, patent, incurved above; stigmatic apex dilated, much divided, penicillate
• Capsule subglobose, membranous, 5-valved, ripening below water surface
• Seeds 6-8, shortly ovoid, black, crustaceous and shiny
• x = 12 (polyploidy)

Nomenclature:

• Aldrovanda L.
  • Linnaeus: 281 (1753)
  • Linnaeus: 136 (1754)
  • Drude: 269 (1891)
  • Diels: 56 (1906)
  • Phillips: 359 (1951)
  • Obermeyer: 187 (1970)
  • Laundon: 62 (1978)
  • Laundon & Basto: 6 (1993)

Distribution & Notes:

• Global: Species 1, widespread in Europe, Asia, Australia and scattered localities in tropical Africa
• Southern Africa: Species 1: Aldrovanda vesiculosa L., Botswana