Boechera atrorubens |
Boechera rubicundula |
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black-flower rockcress, dark-red-flower rockcress, purple sickle-pod rock-cress, sicklepod rockcress |
Mount Day rockcress |
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Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; long-lived; apomictic; caudex 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. |
usually 1 per caudex branch, arising from center of rosette, often somewhat elevated above ground surface on woody base, 1–5 dm, densely pubescent proximally, trichomes simple, 0.5–1 mm, mixed with long-stalked, 2- or 3-rayed ones, 0.1–0.5 mm, moderately to sparsely pubescent 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, 4–8 mm wide, margins denticulate, ciliate along petiole, trichomes to 1 mm, surfaces densely pubescent, trichomes long-stalked, 2–5-rayed, 0.1–0.5 mm. |
Cauline leaves | 7–25, concealing stem proximally; blade auricles 1–4 mm, surfaces of distalmost leaves glabrous. |
8–25, often concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves moderately pubescent. |
Racemes | 6–20-flowered, usually unbranched. |
12–34-flowered, usually unbranched. |
Flowers | ascending at anthesis; sepals pubescent; petals dark reddish purple (drying indigo), 7–9 × 1.5–2 mm, glabrous; pollen ellipsoid. |
ascending at anthesis; sepals pubescent; petals purplish, 6–8 × 2–2.5 mm, glabrous; pollen spheroid. |
Fruiting pedicels | ascending, usually straight, 5–10 mm, glabrous or pubescent, trichomes spreading, simple. |
divaricate-ascending to horizontal, straight, 5–10 mm, pubescent, trichomes spreading, simple and 2-rayed. |
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-ascending to horizontal, not appressed to rachis, not secund, straight or slightly curved, edges parallel, 4–8 cm × 1.7–2.2 mm; valves glabrous; ovules 70–102 per ovary; style 0.1–0.3 mm. |
Seeds | uniseriate, 1.2–1.7 × 0.9–1.2 mm; wing lateral and distal, 0.1–0.2 mm wide. |
uniseriate, 1.4–1.8 × 1–1.3 mm; wing continuous, 0.1–0.2 mm wide. |
Boechera atrorubens |
Boechera rubicundula |
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Phenology | Flowering Apr–May. | Flowering Apr–May. |
Habitat | Rocky summits and sandy loam on sagebrush slopes | Mountain slopes |
Elevation | ca. 600 m (ca. 2000 ft) | ca. 1200 m (ca. 3900 ft) |
Distribution |
OR; WA
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CA |
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.) |
Morphological evidence suggests that Boechera rubicundula is an apomictic species that arose through hybridization between B. arcuata and B. breweri (see M. D. Windham and I. A. Al-Shehbaz 2007 for detailed comparison). It is known only from the type locality on Mt. Day in west-central California. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 366. | FNA vol. 7, p. 404. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis atrorubens, Arabis atriflora, Arabis sparsiflora var. atrorubens | Arabis arcuata var. rubicundula |
Name authority | (Suksdorf ex Greene) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 64. (2006) | (Jepson) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 273. (2007) |
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