19. Streptanthus hesperidis Jepson, Erythea 1: 14. 1893; S. breweri A. Gray var. hesperidis (Jepson) Jepson, Fl. Calif. 2: 33. 1936; Pleiocardia hesperidis (Jepson) Greene, Leafl. Bot. Observ. Crit. 1: 86. 1904. TYPE: United States, California, Knoxville Grade to Lower Lake, 28 Jul 1892, W. L. Jepson 13,355 (holotype, JEPS!). One of the two sheets of this collection carries Jepson’s handwriting and is taken here as the type.

     Herbs, annual, glabrous, mostly yellowish. Stems 1–3 dm, simple or branched about base. Basal leaves not rosulate, short petiolate, soon withered, broadly obovate, 2–3 cm, coarsely and bluntly dentate distally; middle cauline leaves ovate to lanceolate, 1–4 x 0.5–1.5 cm, sessile, amplexicaul, often entire, yellowish, not overlapping; upper leaves reduced, entire. Racemes ebracteate, without a terminal cluster of sterile flowers, secund, rachis flexuous; fruiting pedicels divaricate-ascending, straight, 1–2 mm. Flowers: sepals forming urceolate calyx, yellow-green, ovate-lanceolate, 5–8 mm, glabrous, keeled, recurved or flaring apically; petals whitish with purplish veins, 6–8 mm; blade 2–3 x 1–1.3 mm, not crisped; claw 4–5 mm, about as wide as blade; filaments in 3 pairs of unequal length; adaxial pair united full length, recurved, 6–9 mm; abaxial pair united to middle, 3–5 mm; lateral pair 2–3.5 mm; anthers of adaxial stamens sterile, 0.7–1.2; anthers of abaxial and lateral stamens fertile, 1.7–2.5 mm. Fruits 3–6 cm x 0.9–1.1 mm, divaricate-ascending, nearly straight to rarely arcuate, flattened, somewhat torulose; valves glabrous, with obscure midvein; gynophore 0.2–0.5 mm; replum straight; style 0.1–0.3 mm; stigma entire; ovules and seeds 26–38 per fruit. Seeds oblong, 1.2–1.5 x 0.6–0.8 mm; wing absent or distal and 0.05–0.1 mm wide. 2n = 28.

Flowering: May–Jul.

Habitat: serpentine barrens and associated openings in chaparral-oak woodland and cypress woodland.

Elevation: 250–600 m.

Distribution: United States (California/Lake and Napa counties).