Herbs or subshrubs, perennial; trichomes (1) pointed with surfaces ± smooth, knobby, or notched, (2) retrorsely barbed along shaft and at apex, (3) dendritic, and (4) stinging. Stems erect, sometimes becoming decumbent. Leaves cauline; petiole present or absent; blade ovate-elliptic, lobed, margins entire. Inflorescences headlike thyrses; peduncle to 1 dm. Pedicels not elongating in fruit. Flowers: hypanthium adnate to ovary proximally, free distally; perianth whorls similar; sepals white to yellowish abaxially, yellow adaxially, distinct, linear-lanceolate, longer than petals; petals white to yellowish abaxially, yellow adaxially, distinct, linear-lanceolate, spreading, both surfaces densely hairy; nectary absent; stamens 5, included; filaments monomorphic, dorsiventrally flattened, linear, shorter than anthers; anthers with distal connective extension; staminodes absent; pistil pseudomonomerous, placenta subapical; stigma ovoid, 3–5-lobed, densely hairy. Fruits cypselae, urceolate-ovoid, straight; sepals and petals persistent. Seeds 1, ovoid. x = 7.
sw United States, n Mexico.
In subfam. Gronovioideae, Cevallia is sister to a clade consisting of Fuertesia and Gronovia.
The distinctive stamens, which have inflated, tonguelike extensions beyond the pollen sacs, are unique in the family.