Department of Botany, University of Karachi, Karachi.
Aquatic or paludal, annual or perennial herbs. Leaves alternate, entire or trifoliolate, sometimes peltate, exstipulate. Petiole sheathing. Inflorescence racemose, solitary or fasciculate or involucrate heads. Flowers bisexual, regular. Calyx 5-parted; corolla 5-Iobed, united, lobes valvate or induplicate valvate, fringed or barbed. Stamens 5, alternating with corolla lobes, epipetalous, anthers dithecous, sagitatte and versatile, glands 5, alternating with stamens. Ovary unilocular, borne on somewhat fleshy disc, placentation parietal. Style 1, bifid at the apex. Fruit a unilocular, few to many seeded capsule, 2 or 4 valved. Seeds winged or not with a crustaceous seed coat.
A small family with 5 genera and about 33 species, distributed in temperate regions of both hemispheres. Related to Gentianaceae from which it differs in having alternate leaves, valvate corolla and paludal or aquatic plants. Represented in Pakistan by 2 genera and 2 or 3 species.
Acknowledgements: We are grateful to the United States Department of Agriculture for financing this research under PL-480. Thanks are also due to Mr. I.C. Hedge and Miss. J.Lamond of the Royal Botanic Garden, Edinburgh, for their helpful suggestions.