in N. L. Britton et al., N. Amer. Fl. 34: 170. 1915.
Annuals or perennials, 40–80+ cm. Stems erect, distally branched. Leaves cauline; mostly opposite (distal alternate); blades linear, margins coarsely toothed, faces glabrous (bases ± setaceous, oil-glands scattered along midveins). Heads radiate, in loose, corymbiform arrays or borne singly. Calyculi of 5–8 subulate or pinnatisect bractlets (bearing oil-glands). Involucres ± campanulate, 5–8 mm diam. Phyllaries persistent, 10–12 in 2 series (strongly connate, oblong to linear, margins of outer free to bases, faces of all or outer bearing submarginal and subapical oil-glands). Receptacles convex, pitted (socket margins fimbrillate), epaleate. Ray florets 7–12, pistillate, fertile; corollas lemon to greenish yellow. Disc florets 20–40+, bisexual, fertile; corollas dull yellow, tubes shorter than cylindro-funnelform throats, lobes 5, deltate. Cypselae obpyramidal, glabrous or sparsely strigillose; pappi persistent, of 10–12, 1(–3)-aristate scales in ± 2 series. x = 13.
sc United States.