ACUSTON Raf., Sylva Tell. 131 (1838).

Subshrubs, canescent, densely pubescent throughout. Trichomes sessile or subsessile, with rather slender 8-12 rays, stellate, without webbing between the rays, simple trichomes absent. Multicellular glands absent. Stems erect to ascending, woody, many branched basally, branches terminated in sterile rosettes or leafy flowering shoots, not spiny. Basal leaves petiolate, rosulate, simple, entire; cauline leaves sessile and cuneate to attenuate, not auriculate at base, entire. Racemes few or rarely several flowered, ebracteate, corymbose, slightly elongated in fruit; rachis straight; fruiting pedicels, divaricate to horizontal, straight, densely pubescent, persistent. Sepals oblong, free, deciduous, erect, moderately pubescent, unequal, base of lateral pair saccate; petals yellow, erect at base with flaring blade, longer than sepals; blade obovate to spatulate, apex obtuse; claw strongly differentiated from blade, subequaling or longer than sepals, glabrous, unappendaged, entire; stamens 6, slightly exserted, erect, slightly tetradynamous; filaments glabrous, free, median pairs winged to near apex, lateral pair winged to middle, unilaterally toothed at wing apex; anthers oblong, not apiculate; nectar glands 4, 1 on each side of lateral stamens, median glands absent; ovules 4-12 per ovary; placentation parietal. Fruit dehiscent, capsular silicles, oblong or rarely suborbicular, strongly latiseptate, not inflated, unsegmented; valves thickened, subleathery, veinless, densely pubescent outside, glabrous inside, not keeled, smooth, wingless, unappendaged; gynophore obsolete; replum rounded, concealed by connate valve margins; septum complete, membranous, veinless; style 1-4 mm long, stout, caducous, pubescent along proximal half; stigma capitate, strongly 2-lobed, the lobes connivent, decurrent, opposite replum, unappendaged. Seeds biseriate, winged all around, suborbicular, strongly flattened; seed coat not mucilaginous when wetted; cotyledons accumbent.