Boechera arcuata |
Boechera serotina |
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arching rockcress, elegant rockcress |
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Habit | Perennials; usually long-lived; sexual; caudex often woody (well-developed). | Biennials; short-lived; sexual; caudex not evident. |
Stems | usually 1 per caudex branch, arising from center of rosette, elevated on woody base or from ground surface, (2–)3–8 dm, densely pubescent proximally, trichomes short-stalked, 2-rayed and simple, to 1 mm, pubescent distally. |
usually 1 per plant, arising from center of rosette near ground surface, 4–10 dm, glabrous throughout. |
Basal leaves | blade linear to oblanceolate, 2–7(–12) mm wide, margins usually entire, rarely denticulate, ciliate along petiole, trichomes to 1.5 mm, surfaces densely pubescent, trichomes usually short-stalked, 2–5-rayed (rarely some simple), 0.4–0.8 mm. |
blade obovate to oblanceolate, 5–20 mm wide, margins dentate, not ciliate, surfaces glabrous or subapically puberulent, trichomes simple, 0.1–0.2 mm. |
Cauline leaves | 10–30(–45), often concealing stem proximally; blade auricles 2–5(–6) mm, surfaces of distalmost leaves pubescent. |
30–80, not concealing stem; blade auricles absent, surfaces of distalmost leaves glabrous. |
Racemes | 12–50(–70)-flowered, usually unbranched. |
70–150-flowered, multi-branched. |
Flowers | ascending at anthesis; sepals pubescent; petals purple, 9–14 × 2–4 mm, glabrous or sparsely pubescent (trichomes abaxially); pollen ellipsoid. |
divaricate-ascending at anthesis; sepals glabrous; petals white, 2.8–4 × 0.6–1 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | usually divaricate-ascending, rarely horizontal, gently recurved or straight, 8–22 mm, pubescent, trichomes subappressed, 2–4-rayed. |
divaricate-ascending to horizontal, straight or gently recurved, 6–15 mm, glabrous. |
Fruits | usually divaricate-ascending, rarely horizontal, not appressed to rachis, not secund, usually curved, edges parallel, (6–)8–13 cm × 1.5–2.2 mm; valves glabrous or trichomes relatively few, scattered; ovules 90–250 per ovary; style 0.01–0.5 mm. |
divaricate-ascending to widely pendent, not appressed to rachis, not secund, straight or slightly curved, edges parallel, 4.3–7.9 cm × 1.5–1.8 mm; valves glabrous; ovules 30–42 per ovary; style 0.1–0.2 mm. |
Seeds | uniseriate or sub-biseriate, 1.5–1.7 × 1–1.2 mm; wing continuous, 0.1–0.2 mm wide. |
uniseriate, 1.2–1.7 × 0.7–1 mm; wing continuous or, sometimes, distal (rarely absent), 0.1–0.2 mm wide. |
Flowering | Jul–Sep. |
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Shale | barrens and wooded slopes of crumbling shale; of conservation concern; 100–500 m; Va., W.Va. |
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2n | = 14. |
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Boechera arcuata |
Boechera serotina |
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Phenology | Flowering Mar–Jun. | Flowering Jul–Sep. |
Habitat | Rocky hillsides and cliffs in pine forests and chaparral | Shale barrens and wooded slopes of crumbling shale |
Elevation | 300-1800 m (1000-5900 ft) | 100-500 m (300-1600 ft) |
Distribution |
CA
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VA; WV |
Discussion | Although usually treated as a variety of Arabis (Boechera) sparsiflora (e.g., R. C. Rollins 1993), B. arcuata is easily distinguished from that species by having rachises and fruiting pedicels pubescent with subappressed, 2–4-rayed trichomes and a geographic range limited to southern and western California. By contrast, B. sparsiflora has rachises and fruiting pedicels with spreading, usually simple trichomes (sometimes glabrescent) and an allopatric distribution north and east of the Sierra Nevada. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
boechera serotina is unique among members of the genus in its highly branched inflorescences and late (summer–fall) anthesis. it is in the center for plant conservation’s national collection of endangered plants of conservation concern (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 365. | FNA vol. 7, p. 405. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Streptanthus arcuatus, Arabis holboellii var. arcuata, Arabis maxima, Arabis sparsiflora var. arcuata | Arabis serotina |
Name authority | (Nuttall) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 64. (2006) | (E. S. Steele) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 249. (2007) |
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