Ruppia L.

4 species native Aust.; all states and territories

Submerged, grass-like plants, sometimes occurring abundantly in brackish water. Leaves opposite or alternate, linear or filiform, mostly up to 15 cm long, dilated and sheathing at the base. Flowers bisexual, very small, few in a short spike or cluster enclosed when young in the sheathing bases of the leaves but finally elongated. Perianth absent. Stamens 2, opposite each other, sessile or nearly so, with 2-lobed anthers. Carpels up to 16 but usually 4, free, becoming stalked. Fruit an achene, often beaked.