85. Draba platycarpa Torrey & A. Gray, Fl. N. Amer. 1: 108. 1838.
Draba cuneifolia Nuttall ex Torrey & A. Gray var. platycarpa (Torrey & A. Gray) S. Watson; D. viperensis H. St. John
Annuals; scapose or subscapose. Stems often unbranched, sometimes branched proximally, (0.3-)0.5-3.2(-4) dm, densely hirsute proximally, trichomes simple, 0.9-1.5 mm, and stalked, 2-4-rayed, 0.1-0.6 mm, pubescent distally, trichomes usually branched, rarely simple ones present. Basal leaves rosulate; petiole obscure; blade obovate to spatulate or oblanceolate, 1-4.5 cm × 5-25(-30) mm, margins dentate, surfaces pubescent, abaxially with stalked, (2 or) 3 or 4-rayed trichomes, 0.1-0.6 mm, adaxially with simple, 0.7-1.3 mm, and stalked, 2-4-rayed ones, 0.1-0.5 mm. Cauline leaves (3 or) 4-8(-14); sessile; blade similar to basal. Racemes 12-45(-60)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent, trichomes 2-4-rayed. Fruiting pedicels horizontal to divaricate, straight, 4-9(-11) mm, pubescent as stem. Flowers: (mid- and late-season ones cleistogamous, apetalous); sepals oblong, 1.4-2.2 mm, pubescent; petals white, oblanceolate, (1.7-)2.5-3.5(-4) × 1-2 mm; anthers ovate, 0.2-0.35 mm (shorter in cleistogamous flowers). Fruits obovate-oblong to obovate, plane, flattened, 5-8.2(-9.5) × (2.4-)2.8-3.7(-4) mm; valves pubescent, trichomes simple, antrorse, 0.2-0.5 mm; ovules (28-) 40-70(-82) per ovary; style 0.01-0.2 mm. Seeds ovoid, 0.5-0.7 × 0.3-0.5 mm. 2n = 16, 32.
Flowering Feb-Mar. Rocky hillsides, gravelly and sandy areas, dry plains, roadsides; 0-500 m; Ariz., Ark., Idaho, La., Okla., Oreg., Tex., Wash.
Draba platycarpa is occasionally treated as a variety of D. cuneifolia, but is amply distinct from that species (R. L. Hartman et al. 1975).