Annual, prostrate or erect, glabrous or scaberulous, marshy herbs; stem 15-30 cm high, divaricately branched, pubescent or glabrous, glandular, rooting at the nodes below; leaves simple, opposite, sessile, exstipulate, linear-oblong, acute or obtuse at apex, entire or subcrenate, narrowed at base, pubescent and gland dotted on both surfaces; heads small, shortly peduncled, solitary, heterogamous, axillary, unilateral or in alternate axils, pale or creamy yellow; involucral bracts 4, foliaceous in two, opposite pairs, outer larger than inner, leafy, oblong, obtuse; receptacle convex or conic, enclosing the flowers tipped with glandular hairs; ray florets female, many seriate, fertile, ligulate, 3-4 toothed, disk florets bisexual, fertile or inner sterile, tubular or campanulate, 5 fid; anthers entire, obtuse base; style bifid, arms obtuse, tips hispids; achenes oblong, outer dorsally and inner laterally compressed brown; pappus absent.