Boechera arcuata |
Boechera pinzliae |
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arching rockcress, elegant rockcress |
Pinzl's Rock cress |
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Habit | Perennials; usually long-lived; sexual; caudex often woody (well-developed). | Perennials; long-lived; apomictic; caudex usually woody. |
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. |
1–3 per caudex branch, arising from margin of rosette near ground surface, 0.4–1.6 dm, densely pubescent proximally, trichomes short-stalked, 2–5-rayed, 0.05–0.2 mm, glabrous or sparsely pubescent distally. |
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. |
(petiole glabrous); blade linear-oblanceolate, 1–3 mm wide, margins entire, rarely ciliate proximally, trichomes to 0.5 mm, surfaces densely pubescent, trichomes short-stalked, 2–5-rayed, 0.05–0.2 mm. |
Cauline leaves | 10–30(–45), often concealing stem proximally; blade auricles 2–5(–6) mm, surfaces of distalmost leaves pubescent. |
3–6, not concealing stem; blade auricles 0(–0.3) mm, surfaces of distalmost leaves sparsely to moderately pubescent. |
Racemes | 12–50(–70)-flowered, usually unbranched. |
5–8-flowered, unbranched. |
Flowers | ascending at anthesis; sepals pubescent; petals purple, 9–14 × 2–4 mm, glabrous or sparsely pubescent (trichomes abaxially); pollen ellipsoid. |
ascending at anthesis; sepals pubescent; petals purple, 4–5 × 1–1.5 mm, glabrous; pollen spheroid. |
Fruiting pedicels | usually divaricate-ascending, rarely horizontal, gently recurved or straight, 8–22 mm, pubescent, trichomes subappressed, 2–4-rayed. |
ascending to divaricate-ascending, straight, 2–6 mm, glabrous or sparsely pubescent, trichomes appressed, branched. |
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. |
ascending to divaricate-ascending, not appressed to rachis, not secund, straight, edges parallel, 2.5–4.8 cm × 2.5–3.2 mm; valves glabrous; ovules 26–34 per ovary; style 0.1–0.3 mm. |
Seeds | uniseriate or sub-biseriate, 1.5–1.7 × 1–1.2 mm; wing continuous, 0.1–0.2 mm wide. |
uniseriate, 2.5–3.5 × 1.5–2.5 mm; wing continuous, 0.2–0.9 mm wide. |
Boechera arcuata |
Boechera pinzliae |
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Phenology | Flowering Mar–Jun. | Flowering Jul. |
Habitat | Rocky hillsides and cliffs in pine forests and chaparral | Gravelly granitic soils in alpine and subalpine areas |
Elevation | 300-1800 m (1000-5900 ft) | 3000-3400 m (9800-11200 ft) |
Distribution |
CA
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CA; NV |
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.) |
Of conservation concern. Morphological evidence suggests that Boechera pinzliae is an apomictic hybrid that contains at least one genome derived from B. platysperma; the other parent has not yet been determined. It is most similar to B. elkoensis, from which it differs in having sparsely pubescent (versus glabrous) sepals and basal leaves with stalked (versus sessile or subsessile) trichomes. Boechera pinzliae is known only from the White Mountains in extreme western Nevada (Esmeralda County) and east-central California (Mono County). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 365. | FNA vol. 7, p. 397. |
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 pinzliae |
Name authority | (Nuttall) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 64. (2006) | (Rollins) Al-Shehbaz: Novon 13: 388. (2003) |
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