Fayaz, F. (2011) Encyclopedia of Tropical Plants Firefly Books, New Zealand
Description of the genus
Herbs, often emergent, caulescent in flower, smooth, glabrous; rhizome creeping, submerged, scaly; aerial stem erect, with or without nodes. Leaves radical or cauline, elongated. Inflorescence terminal, cylindric, superposed spike. Flowers numerous, densely crowded, brown, hairy. Fruit a follicle, dehiscing longitudinally by a slit. Seed striate.
Worldwide: Species 29 in marshy and aquatic habitats worldwide.