Boechera shockleyi |
Boechera atrorubens |
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Shockley's Rock cress |
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, (rarely with persistent, crowded leaf bases). | Perennials; usually short-lived; sexual; caudex not woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, (0.8–)2–5 dm, densely pubescent proximally, trichomes short-stalked, 7–12-rayed, 0.1–0.2 mm, densely to sparsely pubescent distally. |
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. |
Basal leaves | blade oblanceolate, 3–10 mm wide, margins entire, not ciliate, surfaces densely pubescent, trichomes short-stalked, 7–12-rayed, 0.1–0.2 mm. |
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. |
Cauline leaves | 14–60, concealing stem for most of length; blade auricles 0.5–4 mm, surfaces of distalmost leaves densely pubescent. |
7–25, concealing stem proximally; blade auricles 1–4 mm, surfaces of distalmost leaves glabrous. |
Racemes | 20–70-flowered, usually unbranched. |
6–20-flowered, usually unbranched. |
Flowers | ascending at anthesis; sepals pubescent; petals lavender, 6–9 × 0.8–1.2 mm, glabrous; pollen ellipsoid. |
ascending at anthesis; sepals pubescent; petals dark reddish purple (drying indigo), 7–9 × 1.5–2 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | divaricate-ascending, straight, 7–28 mm, pubescent, trichomes appressed, branched. |
ascending, usually straight, 5–10 mm, glabrous or pubescent, trichomes spreading, simple. |
Fruits | divaricate-ascending, not appressed to rachis, not secund, usually curved, rarely straight, edges parallel, 4.5–11 cm × 1.5–2 mm; valves glabrous or sparsely pubescent throughout; ovules 140–190 per ovary; style 0.05–0.6 mm. |
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. |
Seeds | sub-biseriate, 1–1.3 × 0.7–0.8 mm; wing distal or, rarely, absent, 0.05–0.1 mm wide. |
uniseriate, 1.2–1.7 × 0.9–1.2 mm; wing lateral and distal, 0.1–0.2 mm wide. |
Boechera shockleyi |
Boechera atrorubens |
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Phenology | Flowering Apr–May. | Flowering Apr–May. |
Habitat | Rock outcrops (primarily dolomite) and gravelly soil in desert scrub, sagebrush, and pinyon-juniper woodlands | Rocky summits and sandy loam on sagebrush slopes |
Elevation | 1200-2200 m (3900-7200 ft) | ca. 600 m (ca. 2000 ft) |
Distribution |
CA; NV; UT
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OR; WA
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Discussion | Boechera shockleyi is a distinctive sexual species recognizable by the combination of strongly overlapping cauline leaves, a dense covering of minute, 7–12-rayed trichomes, and relatively long, curved, divaricate-ascending fruits with sub-biseriate seeds. It is most similar to B. inyoensis, but differs from that species in its narrower (0.8–1.2 versus 1.2–2 mm) petals, eciliate basal leaves with smaller (0.1–0.2 versus 0.2–0.7 mm) trichomes, greater number (140–190 versus 74–134) of ovules per ovary, and shorter (1–1.3 versus 1.7–2 mm) seeds with distal (versus continuous) wings. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 7, p. 406. | FNA vol. 7, p. 366. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis shockleyi | Arabis atrorubens, Arabis atriflora, Arabis sparsiflora var. atrorubens |
Name authority | (Munz) Dorn: Brittonia 55: 3. (2003) | (Suksdorf ex Greene) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 64. (2006) |
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