Prostrate or erect, rough, hirsute, annual herb, often rooting at lower nodes; stem strigose, hirsute with appressed, white hairs; leaves opposite, sessile, linear or oblong-lanceolate, subentire or faintly serrate, narrowed at both ends; peduncles 1-2, axillary or terminal, slender bearing small, white, solitary, heterogamous heads; involucres broadly campanulate; bracts 2-seriate, herbaceous, ovate, obtuse or acute, outer large, broad, equaling or even exceeding the flowers; receptacle flat or nearly so; ray florets female, 2-seriate, fertile or sterile, ligule small, entire or 2-toothed, white, rarely yellow; disk florets bisexual, fertile, tubular, 4-5-fid; stamens 5, epipetalous, syngenecious, anthers sagitate, anther base obtuse; ovary 1 celled, 1-ovuled, solitary, basal, obtuse, style arms elongate, obtuse; achenes of disk florets stouter, laterally subcompressed, tip entire, toothed or 2-aristate; achenes of ray florets narrow, triquetrous, often empty; achenes toothed or aristate, winged on the margin; pappus absent.