Boechera arcuata |
Boechera missouriensis |
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arching rockcress, elegant rockcress |
green 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, 2–7.5 dm, sparsely pubescent proximally, trichomes simple, to 0.5 mm, or 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 oblanceolate, 5–18 mm wide, margins lyrate-pinnatifid, often ciliate-mucronate on lobes, trichomes minute, surfaces glabrous or sparsely pubescent, trichomes simple, 0.1–0.5 mm. |
Cauline leaves | 10–30(–45), often concealing stem proximally; blade auricles 2–5(–6) mm, surfaces of distalmost leaves pubescent. |
10–45, often concealing stem proximally; blade auricles 1–5 mm, surfaces glabrous. |
Racemes | 12–50(–70)-flowered, usually unbranched. |
18–47-flowered, sometimes branched. |
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 glabrous; petals white, 5–10 × 1–1.5 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | usually divaricate-ascending, rarely horizontal, gently recurved or straight, 8–22 mm, pubescent, trichomes subappressed, 2–4-rayed. |
suberect to divaricate-ascending, straight or slightly curved, 5–13 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. |
ascending to divaricate-ascending, not appressed to rachis, not secund, curved, edges parallel, 6–11 cm × 1.5–2 mm; valves glabrous; ovules 60–86 per ovary; style 0.1–1 mm. |
Seeds | uniseriate or sub-biseriate, 1.5–1.7 × 1–1.2 mm; wing continuous, 0.1–0.2 mm wide. |
uniseriate, 1.2–2 × 1–1.2 mm; wing continuous, 0.1–0.4 mm wide. |
Boechera arcuata |
Boechera missouriensis |
|
Phenology | Flowering Mar–Jun. | Flowering Mar–Jun. |
Habitat | Rocky hillsides and cliffs in pine forests and chaparral | Rocky bluffs, wooded slopes, valley bottoms |
Elevation | 300-1800 m (1000-5900 ft) | 50-300 m (200-1000 ft) |
Distribution |
CA
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AR; CT; GA; IL; KY; MA; MI; MN; MO; NC; NY; OK; SC; WI
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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.) |
Boechera missouriensis occasionally has been treated as a variety of B. laevigata. With its significantly longer petals (5–10 versus 3–5 mm) and distinctive, lyrate-pinnatifid basal leaves that persist well beyond anthesis, it warrants recognition as a species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 365. | FNA vol. 7, p. 390. |
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 missouriensis, Arabis laevigata var. heterophylla, Arabis laevigata var. missouriensis, Arabis missouriensis var. deamii, Arabis viridis, Arabis viridis var. deamii |
Name authority | (Nuttall) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 64. (2006) | (Greene) Al-Shehbaz: Novon 13: 387. (2003) |
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