Annuals or perennials, 10-50(-70+) cm. Stems erect or decumbent, branched from bases and/or distally (sometimes rooting at proximal nodes). Leaves cauline; opposite; petiolate or sessile; blades (1- or 3-nerved) lanceolate to lance-linear, bases cuneate, margins serrate to subentire, faces sparsely scabrellous. Heads radiate, in loose, corymbiform arrays or borne singly. Involucres hemispheric, 3-5 mm diam. Phyllaries persistent, 8-12+ in 2-3 series (lanceolate to linear, subequal, thin-herbaceous, spreading in fruit). Receptacles flat to convex, paleate (paleae linear to filiform, not conduplicate, falling with fruits). Ray florets 20-40 (in 2-3+ series), pistillate, fertile; corollas white or whitish. Disc florets 15-30+, bisexual, fertile; corollas white or whitish, tubes much shorter than ampliate, cylindric throats, lobes 4-5, ± deltate. Cypselae obcompressed, weakly 3-4-angled (not winged, epidermes usually corky and rugose to tuberculate); pappi persistent, coroniform (sometimes with 2 teeth). x = 11.