Thysanocarpus pusillus Hooker, Icon. Pl. 1: plate 42. 1837; Athysanus pusillus var. glabrior S. Watson; T. oblongifolius Nuttall

Plants sparsely to densely pubescent proximally, some-times glabrous distally. Stems (0.2-)0.5-3(-5) dm. Basal leaves: petiole 0.1-0.5 cm; blade oblanceolate, obovate, or oblong, 0.3-1.5(-2) cm × (1-)2-6(-8) mm, margins entire or dentate, apex acute to obtuse, surfaces uniformly pubescent, trichomes cruciform and 3-rayed, adaxially sometimes mixed with coarse, simple ones. Cauline leaves 1-6; blade similar and equaling or smaller than basal. Fruiting pedicels slender, (1.5-)2-4(-6) mm. Flowers: sepals 0.5-1 × 0.3-0.7 mm; petals oblong, 1.5-3 × 0.5-1 mm; filaments 0.4-0.6 mm; anthers (0.05-)0.1-0.2(-0.25) mm. Fruits usually orbicular to obovate, rarely broadly oblong, 1-locular, not twisted; valves thin, veins sometimes prominent, usually pubescent, rarely glabrous, trichomes simple, to 0.5 mm, hooked (sometimes restricted to margins, or mixed with smaller, sessile, cruciform or 3-rayed ones); septum absent; ovules 2(-4) per ovary; style 0.05-0.2 mm. Seeds 1, (0.8-)0.9-1.1(-1.2) × (0.5-)0.7-0.9(-1) mm. 2n = 26.

Flowering Feb-Jun. Open grassy slopes, grassy glades in woodlands, chaparral, sandy and gravelly flats, flood plains, rock outcrops, cliffs and ledges, on limestone, serpentine, sandstone, granitic and basaltic substrates; 0-1800 m; B.C.; Ariz., Calif., Idaho, Mont., Nev., Oreg., Wash.; Mexico (Baja California).

Records of Athysanus pusillus for Montana appear to be solely from Ravalli County, and for Nevada from Storey and Washoe counties.