Annual or perennial, commonly several-branched from base, ±glabrous to cottony-pubescent. Leaves narrowly obovate to spathulate, serrate, or rarely entire. Inflorescence a single sessile or minutely pedunculate capitulum, sometimes terminal on ultimate branchlets, not leaf-opposed. Capitula bowl-shaped to cup-shaped or sub-globular, domed or flat-topped; involucral bracts ovate to obovate; receptacle slightly convex, flat, or slightly concave. Fruiting heads firm to hard, persistent to some degree; bracts spreading; receptacle with an underlying pith layer extending slightly below base of involucre. Achenes linear or narrowly cuneoid, obtuse at apex, smooth or scabridulous, 4-or 5-angled with prominent ribs at each angle; ribs terminating in a spongy apical portion usually slightly wider than body of achene; hairs antrorse, subappressed, confined to ribs, often with minutely inrolled or thickened apices.
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