Leafl. W. Bot. 10: 182. 1965.
Annuals; (glaucous, usually with purplish cast), glabrous. Stems unbranched or branched distally, 2–10 dm. Basal leaves (soon withered); rosulate; petiolate; blade 2-pinnatifid or 2-pinnatisect, 3.5–15 cm. Cauline leaves: blade lanceolate, 3–16 cm × 10–40 mm, (smaller distally), base amplexicaul, margins dentate or entire (entire distally). Racemes bracteate below or between proximalmost 1 or 2 flowers. Fruiting pedicels divaricate-ascending, (straight), 4–15 mm. Flowers: calyx urceolate; sepals violet-purple, 6–10 mm, slightly keeled or not, (apex recurved); petals white (with violet veins), 8–11 mm, blade 3–4 × 1.5–2 mm, margins not crisped, (undulate), claw 6–8 mm, about as wide as blade, (apex reflexed); stamens in 3 unequal pairs; filaments (distinct): abaxial pair 4–6 mm, lateral pair 3–4 mm, adaxial pair 7–9 mm; anthers: abaxial and lateral pairs fertile, 3.5–5 mm, adaxial pair partially fertile, 2.5–3 mm; gynophore 1–2 mm. Fruits ascending, smooth, straight or slightly curved, flattened, 6–12 cm × 1.7–2.5 mm; valves each with prominent midvein; replum straight; ovules 60–100 per ovary; style 0.1–1 mm; stigma slightly 2-lobed. Seeds broadly ovoid to suborbicular, 2–2.5 × 1.5–2 mm; wing 0.1–0.3 mm wide, distal 1/2. 2n = 28.
Phenology: Flowering May–Jun.
Habitat: Sparsely rocky sites with vegetation (fractured slate, metamorphic gravels, gruss deposits), oak-pine woodlands
Elevation: 400-1400 m
Streptanthus farnsworthianus is known from Fresno, Kern, Madera, and Tulare counties.