Khadija Aziz and Rubina Dawar
Department of Botany, University of Karachi,
Aquatic or mashy, monoecious perennials with creeping horizontal rhizomes and adventitious fibrous roots, often inflated, simple or branched. Stems stoloniferous to rhizomatous or cormous below, erect or floating, terete, simple or branched. Leaves elongated, linear, stiff or flaccid, alternate, sheathing below. 2-ranked, erect or floating. Flowers unisexual, crowded in separate globose. sessile or pedunculate clusters, the male clusters above the female in each inflorescence. Both male and female flowers with 3-6, scaly segments of perianth. Staminate flower with 3 or more stamens, filaments distinct or connate basally. anthers oblong, basifixed. Pistillate flowers with 1-3 united carpels; ovary superior, shortly stipitate or sessile, 1-2 loculed, ovule 1 in each locule, basal or pendulous; style short, simple or forked; stigmas 1-3, papillose. Fruits sessile-subsessile, drupe like, fusiform, spherical or obovoid in burr-like clusters, 1-2 seeded, indehiscent, narrowed at the base with a spongy endocarp. Seeds with a thin testa and the embryo in the middle of mealy endosperm.
A family with a single genus and c.14 species. Distributed throughout the temperate and arctic regions of the northern hemisphere and in southeastern Australia and New Zealand.
Acknowledgements: We are grateful to the authorities of RAW. K and BM for providing the herbarium and library facilities.