Annuals, 5-250 cm. Stems erect. Leaves mostly cauline (at flowering) proximal opposite (often in rosettes), distal alternate; sessile; blades lanceolate or oblong-linear to linear, margins usually entire, sometimes toothed, faces hirsute to strigose, usually glandular-pubescent as well. Heads usually radiate (sometimes discoid in M. glomerata), in corymbiform, paniculiform, racemiform, or spiciform arrays or in glomerules. Peduncular bracts: pit-glands, tack-glands, and/or spines 0. Involucres ellipsoid, depressed-globose, globose, obconic, ovoid, or urceolate, 1-10+ mm diam. Phyllaries 0 (then outer paleae functioning as phyllaries, sometimes in M. glomerata), or 1-22 in 1 series (lance-linear to lance-attenuate or oblanceolate, herbaceous, each mostly or wholly enveloping a subtended ray ovary, abaxially hirsute and, usually, glandular). Receptacles flat to convex, glabrous or setulose, paleate (paleae persistent or falling readily, in 1 series between rays and discs, ± connate or distinct, phyllary-like, more scarious). Ray florets 0 (sometimes in M. glomerata), or 1-22, pistillate, fertile; corollas yellowish (with maroon bases sometimes in M. elegans; purplish red sometimes in M. sativa). Disc florets 1-80+, bisexual and fertile or functionally staminate; corollas usually yellow, sometimes purplish, tubes shorter than or about equaling funnelform throats, lobes 5, deltate (anthers ± dark purple or yellow to brownish; styles glabrous proximal to branches). Ray cypselae compressed, ± 3-angled, or rarely terete, clavate (often arcuate, basal attachments central or offset, apices sometimes beaked, faces glabrous); pappi 0. Disc cypselae similar, sometimes obovoid (often ± straight, basal attachments central, apices not beaked), sometimes 0; pappi 0. x = 8. Madia is more narrowly circumscribed here than in previous treatments by D. D. Keck (1959) and others. Molecular phylogenetic data have indicated that Madia in those earlier senses is not monophyletic (B. G. Baldwin 1996). As treated here, Madia comprises all members of Keck´s informal 'section Madia' except M. minima (= Hemizonella) (Baldwin 1999b). Most species are reportedly either cross-incompatible or intersterile (J. Clausen 1951).
Heads radiate, the rays pistillate and fertile, yellow, often short, or rarely wanting and the heads discoid; invol bracts subherbaceous, uniseriate, equal, enfolding the achenes, the invol appearing deeply sulcate; receptacle convex, chaffy only near the margin; disk-fls perfect but sometimes sterile; style-branches flattened, with an acute, hairy appendage; ray-achenes generally ±compressed radially, finely striate, commonly incurved, those of the disk similar or empty; pappus none, or a short crown or a few short scales; ±glandular and heavy-scented, annual to perennial herbs with chiefly alternate, entire or merely toothed lvs and small or middle-sized heads. 17, w. N. Amer. and Chile.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.