Herbs or subshrubs, annual or perennial. Stems prostrate, decumbent, ascending, erect, or floating, indumentum of simple trichomes. Leaves opposite, sessile or petiolate; blade lanceolate to ovate, ovate-rhombic, or obovate-rhombic, margins entire. Inflorescences axillary or terminal, sessile or pedunculate, several-flowered cylindric spikes or globose heads, without immediately subtending leaves; bracts and bracteoles scarious. Flowers bisexual; tepals 5, distinct; stamens 3-5; filaments connate basally into tube or short cup; pseudostaminodes 5, alternating with stamens; ovule 1; style 1, ca. 0.2 mm; stigma capitate or rarely 2-lobed. Utricles compressed, ovoid or obovoid, indehiscence. Seeds 1, reddish brown, lenticular or ovoid-oblong.
Fls perfect; sep 5, distinct, unequal, white or greenish; filaments united at least below, the 3-5 antheriferous filaments alternating with 3-5 sterile ones; anthers bisporangiate and unilocular, style solitary, with a capitate stigma; ovule one; utricle membranous, indehiscent; annual or perennial herbs or shrubs with opposite, petiolate or sessile, entire or obscurely denticulate lvs; fls white or greenish, in terminal heads or short spikes. 170, warm reg.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.