CLYPEOLA L., Sp. Pl.: 652 (1753).

Herbs annual. Trichomes sessile, 6–20-rayed, stellate with rigid, appressed rays, those on fruits often with coarse, subsetose, barbellate or smooth, apically hooked or straight simple trichomes. Multicellular glands absent. Stems erect to ascending, sometimes prostrate, simple several basally and/or apically, leafy, not spiny. Basal leaves petiolate, not rosulate, simple, entire; cauline leaves subsessile, cuneate to attenuate, not auriculate at base, entire. Racemes few to several flowered, ebracteate, corymbose, elongated or not in fruit; rachis straight; fruiting pedicels recurved, reflexed, or rarely divaricate, persistent detached from base. Sepals ovate, free, deciduous, suberect, equal, base of lateral pair not saccate; petals yellow, erect and sometimes with flaring blade, shorter or rarely longer than sepals; blade oblanceolate or rarely spatulate, glabrous or rarely sparsely pubescent adaially, apex obtuse or rarely retuse; claw undifferentiated or rarely differentiated from blade, shorter than sepals, glabrous, unappendaged, entire; stamens 6, included, erect, slightly tetradynamous or subequal; filaments winged, appendaged, glabrous, free; anthers ovate, not apiculate; nectar glands 4, lateral, 1 on each side of lateral stamen, median glands absent; ovules 1 per ovary; placentation subapical. Fruit indehiscent, samaroid silicles, ovate or orbicular, strongly latiseptate, not inflated, unsegmented; valves papery to subleathery, veinless, often with coarse, setose, barbellate or smooth, straight or rarely hooked simple trichomes sometimes mixed with minute stellate trichomes or minute simple papillae, often keeled, smooth, winged or wingless, unappendaged; gynophore absent; replum united with valve margin to form fruit wing; septum absent or rarely reduced to rim, veinless; style obsolete or to 3.5 mm long, filiform, persistent; stigma capitate, entire, unappendaged. Seeds aseriate, wingless, ovate to orbicular, strongly flattened; seed coat not mucilaginous when wetted; cotyledons accumbent.