50. Physaria ludoviciana (Nuttall) O’Kane & Al-Shehbaz, Novon. 12: 325. 2002.
Alyssum ludovicianum Nuttall, Gen. N. Amer. Pl. 2: 63. 1818, based on Myagrum argenteum Pursh, Fl. Amer. Sept. 2: 434. 1813, not A. argenteum Vitman 1790; Lesquerella ludoviciana (Nuttall) S. Watson; Vesicaria ludoviciana (Nuttall) de Candolle
Perennials; caudex simple or branched; densely pubescent, trichomes (sessile or short-stalked), 4-7-rayed, rays usually furcate, sometimes bifurcate, (rough-tuberculate throughout). Stems few from base, erect with outer usually decumbent, 1-3.5(-5) dm. Basal leaves (erect); blade narrowly lanceolate to linear or (outer) oblanceolate, (1-)2-6(-9) cm, margins usually entire, rarely shallowly dentate, (inner involute, outer usually flat, base usually with some simple trichomes). Cauline leaves: blade narrowly oblanceolate to linear, (1-)2-4(-8) cm, margins flat or involute. Racemes compact, (elongated and loose in fruit, densely-flowered). Fruiting pedicels (usually recurved), (5-)10-20(-25) mm. Flowers: sepals oblong to broadly elliptic, 4-7(-8) mm, (lateral pair subsaccate, median pair cucullate); petals oblanceolate or obovate, (5-)6.5-9.5(-11) mm, (claw undifferentiated from blade, or blade gradually narrowed to claw). Fruits subglobose or obovoid, usually inflated, sometimes slightly compressed, (3-)4-6 mm; valves densely pubescent, trichomes spreading, usually pubescent inside, trichomes appressed, sessile; ovules (4-)8-12 (-16) per ovary; style 3-4.5(-6.5) mm. Seeds slightly flattened. 2n = 10, 20, 30.
Flowering Apr-Jul(-Aug). Sandy or gravelly soils, steep hillsides, prairie pastures, clay slopes, limestone outcrops, sand dunes, open plains, sandy bluffs, rocky flats, white tuff sands; 0-1900 m; Ariz., Calif., Colo., Ill., Iowa, Kans., Minn., Mont., Nebr., Nev., N.Mex., N.Dak., Okla., S.Dak., Utah, Wis., Wyo.
Material previously reported as Physaria ludoviciana from Canada (Alberta, Manitoba, Saskatchewan) is here included in 6a. P. arenosa subsp. arenosa. Lesquerella argentea (Pursh) MacMillan is a later homonym that has been used for P. ludoviciana.