Boechera atrorubens |
Boechera fructicosa |
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black-flower rockcress, dark-red-flower rockcress, purple sickle-pod rock-cress, sicklepod rockcress |
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Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; short-lived; apomictic; caudex usually not woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 0.8–6 dm, sparsely pubescent proximally, trichomes short-stalked and simple, (scattered), 2-rayed, 0.1–0.15 mm, glabrous distally. |
3 to many per caudex branch, arising from margin of rosette near ground surface, 3.5–6 dm, pubescent proximally, trichomes short-stalked, 2–4-rayed, 0.2–0.3 mm, glabrous distally. |
Basal leaves | blade oblanceolate, 4–10 mm wide, margins usually dentate, not ciliate, surfaces densely pubescent, trichomes short-stalked, 3- or 4-rayed, 0.1–0.2 mm. |
blade oblanceolate, 3–7 mm wide, margins dentate, ciliate proximally, trichomes (simple), to 0.3 mm, surfaces pubescent, trichomes short-stalked, 4–8-rayed, 0.05–0.2 mm. |
Cauline leaves | 7–25, concealing stem proximally; blade auricles 1–4 mm, surfaces of distalmost leaves glabrous. |
5–10, not concealing stem; blade auricles 0.5–1 mm, surfaces of distalmost leaves glabrous. |
Racemes | 6–20-flowered, usually unbranched. |
10–18-flowered, usually unbranched. |
Flowers | ascending at anthesis; sepals pubescent; petals dark reddish purple (drying indigo), 7–9 × 1.5–2 mm, glabrous; pollen ellipsoid. |
divaricate-ascending at anthesis; sepals pubescent; petals lavender, 4–6 × 1–1.5 mm, glabrous; pollen spheroid. |
Fruiting pedicels | ascending, usually straight, 5–10 mm, glabrous or pubescent, trichomes spreading, simple. |
divaricate-descending, straight, 5–10 mm, glabrous. |
Fruits | ascending, not appressed to rachis, not secund, curved or straight, edges parallel, (4–)6–12 cm × 1.7–2.2 mm; valves glabrous; ovules 80–100 per ovary; style 0.2–0.5 mm. |
divaricate-descending, not appressed to rachis, not secund, curved, edges parallel, 4–6 cm × 1.5–1.8 mm; valves glabrous; ovules 60–70 per ovary; style 0.1–0.4 mm. |
Seeds | uniseriate, 1.2–1.7 × 0.9–1.2 mm; wing lateral and distal, 0.1–0.2 mm wide. |
uniseriate, 1.5–2 × 1–1.3 mm; wing distal, ca. 0.1 mm wide. |
Boechera atrorubens |
Boechera fructicosa |
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Phenology | Flowering Apr–May. | Flowering Jun–Jul. |
Habitat | Rocky summits and sandy loam on sagebrush slopes | Dry, disturbed soil |
Elevation | ca. 600 m (ca. 2000 ft) | ca. 2000 m (ca. 6600 ft) |
Distribution |
OR; WA
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WY |
Discussion | Boechera atrorubens is often treated as a variety of B. sparsiflora (e.g., R. C. Rollins 1993), it is readily separated from that species by having proximal stems sparsely (versus densely) pubescent with much smaller (0.15 versus 1.5 mm) trichomes. The two taxa rarely grow in proximity and, in areas where they are sympatric, B. atrorubens is further distinguished by its narrower (1.5–2 versus 2–5 mm) petals that are dark reddish purple to indigo (versus lavender or white). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Boechera fructicosa is known only from the type collection (A. & E. Nelson 5681) taken near Undine Falls in Park County. Multiple plants are represented (comprising the holotype and four isotypes), though one specimen with the same number at RM is B. stricta. Although the exact parentage of this apomictic hybrid remains in doubt, it is virtually certain that B. microphylla contributed at least one genome. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 366. | FNA vol. 7, p. 379. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis atrorubens, Arabis atriflora, Arabis sparsiflora var. atrorubens | Arabis fructicosa |
Name authority | (Suksdorf ex Greene) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 64. (2006) | (A. Nelson) Al-Shehbaz: Novon 13: 385. (2003) |
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