Aquatic or marshy, annual herbs with fibrous roots; stem usually condensed or elongate, branched, densely leafy; leaves capillary, apperently in rosette, narrow, linear-subulate, acute, entire; scapes axillary, many, erect, slender, glabrous; heads very small, ovoid, white or blackish white, unisexual or monoecious; involucral bracts very small, glabrous, scarious, oblong, cuneate, obtuse; floral bracts grey, closely appressed, linear-elliptic, glabrous; male flowers: sepals-3, free or connate, glabrous; petals 2-3, equal or unequal, minute, glabrous or sparsely hairy; stamens-6 or fewer, some reduced to filaments only, 3 adnate to petals, anthers dorsifixed, white; pistillode minute or absent; female flowers: sepals 2-3, caducous, linear, black with a long stalk, jointed between sepals and ovary; petals-3, linear, persistent with a black gland on the disk; ovary long, stipitate, 3 or 2-celled, ovule solitary, style short, stigma with 2-3, slender lobes; capsule deeply 3-lobed, membranous, loculicidal; seeds minute, pendulous, ovoid-ellipsoid, smooth, reddish-brown.