Description: Fully submerged marine or estuarine rhizomatous perennials with strap-like leaves and submerged flowers.
Leaves with a sheathing base, ligulate. The sheath fibres persistent and often washed up as characteristic 'fibre-balls'.
Inflorescence a terminal cluster of spikes on a leafless stem. Lower spikes subtended by leaf-like bract and 2 or more bladeless bracts. Each subsequent spike subtended by outer bracts with progressively shorter blades as well as the 2 or more bladeless bracts. Flowers bisexual, rarely male, pollination occurring under water. Perianth absent. Stamens 3, sessile; anthers 2-locular and lobes well separated by the broad connective, dehiscing by longitudinal slits; pollen thread-like. Carpel solitary, superior, with 1 ovule.
Fruit with a spongy pericarp, floating when first released, 1-seeded.
Distribution and occurrence: World: 1 genus, 9 species, Australia & Mediterranean region. Australia: 8 species (endemic), N.S.W., Vic., Tas., S.A., W.A.
Angiosperm Phylogeny Website (Family: Posidoniaceae, Order: Alismatales)
Text by S. W. L. Jacobs
|One genus in NSW: Posidonia|