STREPTANTHELLA Rydberg, Fl. Rocky Mts., 364, 1062. 1917.
Ihsan A. Al-Shehbaz
Tribe: Thelypodieae Prantl in Engler & Prantl, Nat. Pflanzenfam. III. 2: 155. 1891.
Name derivation: diminutive of Streptanthus, another genus in the Brassicaceae.
Type species: S. longirostris (S. Watson) Rydberg (based on Arabis longirostris S. Watson).
Herbs, annual, often glaucous. Trichomes absent. Muticellular glands absent. Stems erect or ascending, often branched above. Basal leaves soon withered; cauline leaves short-petiolate, not auriculate at base, simple, entire, dentate, sinuate, or pinnatifid; uppermost sessile, often entire. Racemes several-flowered, ebracteate, lax, elongated considerably in fruit; rachis straight; fruiting pedicels recurved to reflexed, persistent. Sepals oblong, erect, caducous, glabrous, unequal, base of lateral pair subsaccate. Petals white or yellow, often with purplish veins, slightly exceeding sepals; blade spatulate, crisp at margin, obtuse at apex; claw well-differentiated from blade, shorter than calyx, glabrous, unappendaged, entire. Stamens 6, slightly exserted, in 3 pairs of unequal length; filaments wingless, unappendages, glabrous, free; anthers ovate to oblong, apiculate at apex. Nectar glands lateral, semi-annular, subtending lateral stamens, median glands absent. Ovules (12–)16–28(–34); placentation parietal. Fruits dehiscent siliques, linear, latiseptate, not inflated, unsegmented; valves papery, with a prominent midvein extending full length, glabrous, not keeled, smooth, wingless, unappendaged; gynophore absent; replum rounded to slightly flattened, visible; septum complete, veinless; style well-developed, united with valves and replum apices, persistent; stigma subentire. Seeds uniseriate, winged, oblong, flattened; seed coat not mucilaginous when wetted; cotyledons incumbent. x = 7.
Monospecific: N Mexico, W United States.