30. Streptanthus platycarpus A. Gray, Pl. Wright.5: 10. 1853; Erysimum platycarpum (A. Gray) Kuntze, Revis. Gen. Pl. 2: 933. 1891. TYPE: United States, Texas, stony hills, Valley of the Pecos, Jun 1851, Charles Wright 844 (holotype, GH!; isotypes, GH!, MO!, NY!).
Streptanthus sparsiflorus Rollins, Contr. Gray Herb. 200: 190. 1970. TYPE: U.S.A. Texas: Culberson Co., S fork of McKittrick Canyon, Guadalupe Mts., 21 Jun 1964, Donovan S. Correll & C. Hanson 29805 (holotype, GH!; isotypes, LL!, UC!).
Herbs, annual, glaucous, glabrous throughout except sometimes for uppermost stems and pedicels. Stems 1.2–10 dm, single, usually branched, glabrous or sparsely pilose distally. Basal leaves subrosulate, petiolate, soon withered, oblanceolate in outline, 4–20 cm, sinuate to lyrate or pinnatifid; middle cauline leaves ovate, 1.5–15 x 0.5–6 cm, sessile, auriculate to amplexicaul, entire or sinuate-dentate; upper leaves ovate, entire, smaller. Racemes ebracteate or lowermost few flowers bracteate, very rarely bracteate throughout, lax, without a terminal cluster of sterile flowers; fruiting pedicels divaricate to ascending, straight, glabrous or pilose, 0.7–3.5 cm. Flowers: sepals forming campanulate calyx, purple to deep maroon, lanceolate, 8–12 mm, not keeled; petals lavender or purplish lavender, 1.6–2.7 cm; blade spreading to reflexed, not crisped, 1–1.8 cm x 6–9 mm; claw crisped, 6–10 mm; filaments in 3 pairs of unequal length, free; adaxial pair 5–8 mm; abaxial pair 4–6 mm; lateral pair 3–5 mm; anthers of all stamens fertile, 4.5–6 mm. Fruits 4–9.5 cm x 4.5–6 mm, erect to divaricate-ascending, strongly flattened, straight, not torulose; valves glabrous, with a distinct midvein; gynophore 0.3–1 mm; replum straight; style 0.5–2 mm; stigma strongly 2-lobed; ovules and seeds 26–42 per fruit,. Seeds orbicular to oblong-orbicular, 4.5–5 x 4–5 mm; wing continuous, 0.7–1.2 mm wide. 2n = 28.
Habitat: cliff ledges, often on limestone, rocky sites, roadsides, rocky creek beds.
Elevation: 400–1200 m.
Distribution: Mexico (Coahuila), United States (Texas).