Source:
SSA
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).
Distribution:
Species 2, both from subtropical and temperate South America; *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). 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.
Classification:
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