1 gen., widespread on the coasts of warmer seas

Posidonia K.D.Koenig.

8 species endemic Aust.; NSW, Vic., Tas., S.A., WA

Posidonia australis Hook.f.

Submerged, marine plant with a creeping rhizome. Leaves linear, up to 1 cm wide, up to 1 m long; leaf bases sheathing, persistent, fibrous, covering the stem. Flowers bisexual, in a compound spike with a long floral leaf at the base of the whole and shorter floral leaves at the bases of each single spike. Perianth absent. Stamens 3; anther lobes dark coloured, separated by an extended ± awned green connective. Ovary superior, 1-locular, sessile; stigma 3–4-lobed. Fruit c. 2 cm long, obliquely ovoid-acuminate, fleshy, indehiscent. Coast, in bays and estuaries below low tide mark. Fl. spring–summer