Streptanthus longifolius Bentham, Pl. Hartw., 10. 1839; Heterothrix longifolia (Bentham) Rydberg; Lamprophragma longifolium (Bentham) O. E. Schulz; Pennellia hunnewellii Rollins; P. mcvaughii Rollins; Thelypodium anisopetalum Greene; T. longifolium (Bentham) S. Watson

Stems simple or few from base, 4-15 dm, pubescent proximally, trichomes simple and long-stalked, 2-rayed, mixed with smaller, dendritic ones. Basal leaves caducous; petiole to 3 cm; blade spatulate to oblanceolate, 1.8-3 cm × 2-4 mm, margins dentate, sinuate, incised, or runcinate, surfaces pubescent, trichomes stalked, forked and dendritic, mixed with fewer, simple ones. Cauline leaves (distal) sessile; blade linear, 3-9.2 cm × 0.8-5 mm, surfaces glabrous or glabrate. Racemes secund, 1.6-7.9 dm in fruit. Fruiting pedicels slightly descending, recurved, 5-13 mm. Flowers (slightly zygomorphic, receptacle asymmetric); sepals purple or green, oblong, 4-9 × 1.5-4 mm, (adaxial largest); petals lavender to purple apically, spatulate, (4-)5-7(-12) × 1-3 mm, (adaxial largest); filaments 4-9 mm; anthers 1-1.2(-2) mm. Fruits pendent, straight or nearly so, 5-10 cm × 1-1.2 mm, slightly latiseptate; valves glabrous; septum transparent; ovules 150-250 per ovary; style 0.5-1.2 mm. Seeds biseriate, plump, not winged, oblong, 0.7-1.3 × 0.4-0.5 mm; seed coat mucilaginous when wetted; cotyledons incumbent. 2n = 16.

Flowering Jul-Oct. Mixed pine-oak forest, limestone hills, rocky outcrops and meadows, stream banks, shaded ravines; 1400-3400 m; Ariz., N.Mex., Tex.; Mexico; Central America (Costa Rica, Guatemala).