69. Physaria prostrata (A. Nelson) O’Kane & Al-Shehbaz, Novon. 12: 327. 2002.
Lesquerella prostrata A. Nelson, Bull. Torrey Bot. Club 26: 124. 1899
Perennials; caudex branched; densely pubescent, trichomes (usually sessile, rarely short-stalked), several-rayed, rays furcate or bifurcate, (umbonate, tuberculate throughout). Stems several from base, usually prostrate, rarely decumbent, (unbranched, often purplish, sparsely pubescent), to 1.5 dm. Basal leaves: blade deltate, hastate, or, less often, rhombic to elliptic, 1-5 cm, margins entire (often partially involute). Cauline leaves: (proximal shortly petiolate); blade linear to oblanceolate, 0.5-1.5 cm, margins entire. Racemes loose, elongated. Fruiting pedicels (ascending, slightly sigmoid to straight), 5-10 mm. Flowers: sepals (often purplish), oblong, lanceolate, or ovate, 4-6 mm, (median pair thickened apically); petals spatulate or cuneate, 5-8(-9) mm, (margins undulate). Fruits ovoid or ellipsoid, slightly compressed, 3-5(-6) mm, (base often gibbous); valves pubescent, trichomes loose, furcate near their bases and spreading, sometimes sparsely pubescent inside; ovules 4(-8) per ovary; style 1.5-4 mm. Seeds flattened.
Flowering May-Jun. Whitish sand and small rocks on steep slopes, dry hillsides, windswept knolls, shaley slopes; of conservation concern; 1800-2500 m; Idaho, Utah, Wyo.
Physaria prostrata is sometimes found on igneous substrates, which is unusual for the genus.