Description:

• Permanently submerged, attached, much-branched, densely leafy, dioecious perennials
• Leaves in whorls of 3 or more, sessile, linear to widely lanceolate, 1-nerved, margins without fibre cells, serrulate, apex acute, terminating in a single spine
• Inflorescence in axil of foliage leaves; spathe sessile or subsessile, of 2 united bracts
• Flowers unisexual, arising from spathes situated in upper leaf axils; each flower with a thread-like hypanthium; sepals 3; petals 3, large, 2-3 times longer than sepals and alternating with them
• Male flowers 2 or 4, held above water surface on rigid pedicels; sepals ovate, spreading, green; petals obovate to suborbicular, white; stamens 9 or rarely more; filaments club-shaped, orange, glandular, much longer than anthers, central 3 erect and opposite sepals, outer 6 in 2 whorls of 3 and upcurved; anthers unequal, each theca dehiscing longitudinally into two equal valves; staminodes 0; pollen liberated in monads; pistillodium 3-lobed, green
• Female flowers solitary, similar to male flowers; stamens replaced by 3 linear, yellow to orange staminodes, elongated hypanthium bearing flower above water surface; ovary of 3 carpels; enclosed in base of hypanthium, placentas parietal; ovules several; styles 3, flattened, variously bifid or trifid
• Fruit ellipsoidal, irregularly dehiscent
• Seeds long, spindle-shaped
• x = 12, 23 (1 report each, polyploidy)

Nomenclature:

• *Egeria Planch.
  • Planchon: 79 (1849)
  • Obermeyer: 100 (1966)
  • Aston: 215 (1973)
  • Cook & Urmi-König: 73 (1984)
  • Cook: 97 (1990)

Distribution & Notes:

• Global: Species 2, both from subtropical and temperate South America
• Southern Africa: *Egeria densa Planch. has been introduced into KwaZulu-Natal, probably during Medley Wood's time when a submerged aquatic was needed as an 'oxygen plant' for the fish introduced to combat malaria-carrying mosquito larvae; also recorded from the Baakens River in Port Elizabeth (Eastern Cape), a sewerage pond in Bloemfontein (Free State) and a dam in Stellenbosch (Western Cape)

Additional Notes:

• This potentially serious weed, is a popular aquarium or outdoor pond plant and is sold at various nurseries and aquarium shops
• It is often confused with some of the species of Lagarosiphon, but it is more robust and the leaves are in definite whorls