Index Seminum (Bratislave) 1837: . 1837.
Annuals, 4–62 cm. Stems erect, branched distally. Leaves mostly cauline; proximal opposite, distal alternate; ± sessile; blades linear, margins entire or toothed, faces hirsute or villous and (distal leaves) sparsely glandular-pubescent. Heads radiate, borne singly or in loose, ± corymbiform arrays. Peduncular bracts: pit-glands, tack-glands, and/or spines 0 at tips. Involucres ± campanulate to cylindric or ellipsoid, 3–12+ mm diam. Phyllaries 3–8 in 1 series (± lance-linear, herbaceous, each fully enveloping a ray ovary, abaxially hirsute or villous and sparsely glandular-pubescent or eglandular). Receptacles flat to convex (setulose), paleate (paleae falling, in 1 series between rays and disc, distinct). Ray-florets 3–8, pistillate, fertile; corollas yellow, turning reddish (lobes ± parallel). Disc-florets 4–35, bisexual and fertile; corollas yellow to reddish, tubes ± equaling narrowly funnelform throats, lobes 5, lance-deltate (anthers ± dark purple; styles glabrous proximal to branches). Ray cypselae (black) obcompressed, clavate (10-ribbed, straight, basal attachments centered, apices beakless, faces glabrous or ± scabrous); pappi 0. Disc cypselae (brown to black) similar to rays (± scabrous); pappi of 10 white, oblong scales (apices obtuse). x = 8.
w North America, nw Mexico