"Heads radiate or discoid, the rays when present few, often 8, sterile, generally neutral, yellow or less often white or pink; invol bracts biseriate and dimorphic, the outer ± herbaceous, often very large, the inner membranous, often striate; receptacle flat or slightly convex, its bracts narrow, flat or nearly so; disk-fls perfect and fertile; style-branches flattened, with externally hairy, usually short appendage; achenes flattened parallel to the invol bracts, but not (or scarcely) winged, or sometimes almost regularly tetragonal, rarely subterete; pappus of (1)2–4(6) awns or teeth, commonly retrorsely barbed, but sometimes antrorsely barbed or even barbless, in a few spp. obsolete; herbs (ours) with opposite, simple to dissected lvs. 200, cosmop.Thelesperma megapotamicum (Spreng.) Kuntze, of the Great Plains, has been reported as adventive in Ill. and Mo. It is a glabrous perennial with the lvs once or twice pinnatifid into slender segments; the discoid (or inconspicuously radiate) heads terminate long, naked peduncles; the outer invol bracts are very short, and the inner ones are connate to the middle or above; the wingless achenes have a pappus of 2 retrorsely barbed awn-scales. (T. gracile)"
Achenes compressed or angled, striate-sulcate, ribbed, unmargined or margins narrowly winged or callose-thickened; at apex with or without aristae, aristae with or without antrorse and or retrorse barbs.
Ray florets neuter with aristate or exaristate ovary or pistillate and fertile with well developed achenes and aristae, rays yellow or orange, rarely white (B. pilosa L.) or lemon-yellow, striate; disc florets yellow to brownish, corolla 5-lobed
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