Annuals, to 60 cm. Stems erect, branched. Leaves cauline; mostly alternate, proximal sometimes opposite; petiolate or sessile; blades narrowly oblong, oblanceolate, or lance-linear, margins sinuate-dentate or entire, faces loosely to densely woolly. Heads usually radiate (sometimes obscurely disciform in M. congdonii, usually borne singly (in corymbiform arrays in M. congdonii). Involucres hemispheric, 5-13 mm diam. Phyllaries persistent, 4-11 in 1 series (usually spreading, reflexed in fruit in M. congdonii, distinct or connate with distinct tips, elliptic to oblanceolate, herbaceous to membranous or indurate, bases flat or cupped, apices acute to acuminate, abaxial faces woolly, usually with black hairs toward tips). Receptacles convex to conic, smooth or pitted, glabrous, epaleate. Ray florets 4(-7, inconspicuous, corollas ± lacking laminae) or (7-)8(-11), pistillate, fertile; corollas usually yellow, sometimes cream in M. major (each lamina opposed by an adaxial lobule or tooth). Disc florets 20-100, bisexual, fertile; corollas yellow (glandular or with nonglandular hairs); tubes cylindric to cylindro-funnelform, about equaling gradually or abruptly dilated, narrowly to broadly funnelform throats, lobes (4-)5, ± deltate (anther appendages usually widest at bases, glandular; style-branch appendages deltate). Cypselae obcompressed or ± prismatic, 3-angled (ray or peripheral) or 2- or 4-angled (disc); pappi usually 0 (persistent, of 2-4+ spatulate, erose to laciniate scales in M. congdonii). x = 13.