Boechera arcuata |
Boechera depauperata |
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arching rockcress, elegant rockcress |
soldier rockcress |
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Habit | Perennials; usually long-lived; sexual; caudex often woody (well-developed). | Perennials; usually long-lived; (cespitose); apomictic; caudex 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. |
usually 1 per caudex branch, arising from center of rosette near ground surface, 0.5–1.5(–2) dm, densely pubescent proximally, trichomes short-stalked, 4–8-rayed, 0.07–0.4 mm, usually sparsely pubescent distally, rarely glabrous. |
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 narrowly oblanceolate, 0.7–3(–5) mm wide, margins entire, sometimes ciliate proximally, trichomes to 0.4 mm, surfaces densely pubescent, trichomes short-stalked, 5–8-rayed, 0.05–0.25 mm. |
Cauline leaves | 10–30(–45), often concealing stem proximally; blade auricles 2–5(–6) mm, surfaces of distalmost leaves pubescent. |
3–7, not concealing stem; blade auricles 0.5–1.5 mm, surfaces of distalmost leaves usually pubescent, rarely glabrous. |
Racemes | 12–50(–70)-flowered, usually unbranched. |
9–23-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 lavender to purplish, 3.5–5 × 0.8–1.2 mm, glabrous; pollen spheroid. |
Fruiting pedicels | usually divaricate-ascending, rarely horizontal, gently recurved or straight, 8–22 mm, pubescent, trichomes subappressed, 2–4-rayed. |
divaricate-ascending, straight, 1.5–7 mm, usually pubescent, rarely glabrous, 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. |
divaricate-ascending, not appressed to rachis, not secund, straight, edges parallel, 1.7–3.5(–4.5) cm × 1–1.5 mm; valves glabrous; ovules 32–44 per ovary; style 0.05–0.2 mm. |
Seeds | uniseriate or sub-biseriate, 1.5–1.7 × 1–1.2 mm; wing continuous, 0.1–0.2 mm wide. |
uniseriate, 1.2–1.5 × 1–1.2 mm; wing continuous, 0.1–0.15 mm wide. |
Boechera arcuata |
Boechera depauperata |
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Phenology | Flowering Mar–Jun. | Flowering Jun–Jul. |
Habitat | Rocky hillsides and cliffs in pine forests and chaparral | Exposed ridges and talus slopes in subalpine and alpine habitats |
Elevation | 300-1800 m (1000-5900 ft) | 2700-3900 m (8900-12800 ft) |
Distribution |
CA
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CA; NV
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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.) |
Morphological evidence suggests that Boechera depauperata is an apomictic species that arose through hybridization between B. lemmonii and B. paupercula (see M. D. Windham and I. A. Al-Shehbaz 2007 for detailed comparison). It is known in California from Fresno, Mono, and Tulare counties and in Nevada from Washoe County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 365. | FNA vol. 7, p. 373. |
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 depauperata, Arabis lemmonii var. depauperata |
Name authority | (Nuttall) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 64. (2006) | (A. Nelson & P. B. Kennedy) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 262. (2007) |
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