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Annual or perennial herbs, or shrubs. Stems usually many-branched, foliose, glabrous or hairy. Leaves cauline, opposite or rarely alternate (not in Australia), usually petiolate, simple or ternately to pinnately compound. Inflorescence of terminal, solitary or loosely cymose capitula, pedunculate. Capitula discoid or radiate, usually small; involucral bracts ±free, in 2–5 series; outer bracts ±foliaceous, usually linear to spathulate, lanceolate or oblanceolate; inner bracts membranous, similar to outer ones; receptacle flat or slightly convex; paleae narrow, membranous, caducous. Ray florets sterile, rarely bisexual (B. pilosa), few or absent, yellow or white. Disc florets bisexual, fertile, numerous, 5-lobed, yellow or greenish. Achenes frequently dimorphic, linear to oblong-cuneate, laterally compressed or 4-angled, ribbed; beak absent. Pappus of 2–4 stiff, retrorsely barbed awns.
Annual or perennial herbs or shrubs. Leaves opposite, simple or variously compound with segments linear to broadly ovate. Capitula radiate, terminal, solitary or arranged in cymes; involucre of usually green outer phyllaries and variously coloured inner phyllaries; paleae membranous, usually oblong-linear, 2–many-striate. 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. 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.
Annual or perennial herbs. Lvs opposite, simple and entire to pinnately or ternately dissected or compound. Capitula pedunculate, solitary or in loose cymes. Involucral bracts in 2 rows; outer row usually foliaceous; inner row membranous. Receptacle flat or slightly convex; scales present. Either outer florets ligulate, female or sterile, and white, yellow or pink, or all florets tubular and ☿. Achenes all similar, square or flattened in section but not winged; pappus of (0)-2-5 awns usually with retrorse barbs.
Capitula solitary, or infl. compound. Phyll. in 2 series. outer foliaceous, inner membr.; receptacle ± flat, with chaffy deciduous scales. Ray-florets ligulate, neuter, or absent; disk-florets tubular, perfect. Achenes us. 4-angled, pappus of 2 to 4 barbed bristles. Annual to perennial herbs with opp. lvs. A widespread genus of some 200 spp., mainly of America.
