This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Annual or perennial, mostly acaulescent or short-stemmed, rarely stoloniferous herbs, with basal, or, in the caulescent species, opposite or alternate leaves, and small perfect polygamous or monoecious flowers, bracteolate in dense terminal long-scaped spikes or heads, or rarely solitary. Calyx 4-parted, inferior, persistent, the segments imbricated. Corolla hypogynous, scarious or membranous, mostly marcescent, 4-lobed. Stamens 4 or 2 (only 1 in an Andean genus), inserted on the tube or throat of the corolla; filaments filiform, exserted or included; anthers versatile, 2-celled, the sacs longitudinally dehiscent. Ovary sessile, superior, 1-2-celled, or falsely 3-4-celled. Style filiform, simple, mostly longitudinally stigmatic. Ovules 1-several in each cavity of the ovary, peltate, amphitropous. Fruit a pyxis, circumscissile at or below the middle, or an indehiscent nutlet. Seeds 1-several in each cavity of the fruit; endosperm fleshy; cotyledons narrow.
Three genera and over 225 species, of wide geographic distribution. Flowers in terminal spikes or heads; fruit a pyxis.
Flowers monoecious, the staminate solitary, peduncled, the pistillate sessile among the linear leaves; fruit indehiscent.