This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", 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..
An annual diffusely branched glabrous or cobwebby-pubescent herb, with alternate peti-oled irregularly toothed leaves, and small sessile bractless perfect or pistillate flowers in panicled interrupted spikes. Calyx 5-lobed, the lobes keeled in flower, a thin horizontal irregularly dentate wing developing below them in fruit. Stamens 5. Styles 2-3. Fruit (except its summit) enclosed by the calyx, depressed. Seed horizontal; embryo a complete ring in the mealy endosperm. [Greek, circle-border, alluding to the calyx-wing.]
A monotypic genus of north central North America.
Pale green or becoming dark purple, bushy-branched, 6'-2o' high, the stem and branches angular and striate. Leaves lanceolate, mostly acuminate at the apex, narrowed into slender petioles, irregularly sinuate-dentate with acute teeth, 1'-3' long or the upper much smaller; spikes numerous in terminal panicles, loosely flowered, 1'-3' long, slender; fruit, including the winged calyx, 2" broad; calyx-lobes not completely covering the summit of the utricle, which appears as a 5-rayed area.