Boechera arcuata |
Boechera laevigata |
|
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arching rockcress, elegant rockcress |
smooth 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. |
1 per plant, arising from center of rosette near ground surface, (1.5–)3–11 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, (4–)10–40 mm wide, margins serrate or dentate, ciliate-mucronate on teeth, trichomes often minute, surfaces glabrous or sparsely pubescent, trichomes simple, 0.1–0.6 mm. |
Cauline leaves | 10–30(–45), often concealing stem proximally; blade auricles 2–5(–6) mm, surfaces of distalmost leaves pubescent. |
7–15, often concealing stem proximally; blade auricles 3–12(–17) mm, surfaces of distalmost leaves glabrous. |
Racemes | 12–50(–70)-flowered, usually unbranched. |
16–45-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, 3–5 × 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 to slightly curved, 5–23 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, not appressed to rachis, rarely somewhat secund, curved, edges parallel, (4–)6–11.7 cm × 1–2 mm; valves glabrous; ovules 50–80 per ovary; style 0.1–0.7(–1) mm. |
Seeds | uniseriate or sub-biseriate, 1.5–1.7 × 1–1.2 mm; wing continuous, 0.1–0.2 mm wide. |
uniseriate, 1.2–2.2 × 0.8–1.4 mm; wing continuous, 0.1–0.3 mm wide distally. |
2n | = 14. |
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Boechera arcuata |
Boechera laevigata |
|
Phenology | Flowering Mar–Jun. | Flowering Mar–May. |
Habitat | Rocky hillsides and cliffs in pine forests and chaparral | Rocky bluffs, cedar glades, wooded hillsides, floodplains |
Elevation | 300-1800 m (1000-5900 ft) | 100-500 m (300-1600 ft) |
Distribution |
CA
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AL; AR; CT; DC; DE; GA; IA; IL; IN; KY; MA; MD; MI; MO; NC; NH; NJ; NY; OH; OK; PA; SC; TN; VA; VT; WI; WV; ON; QC |
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.) |
The taxon sometimes treated as Arabis laevigata var. missouriensis is here recognized as a separate species (Boechera missouriensis) based on its significantly longer petals (5–10 versus 3–5 mm) and distinctive, lyrate-pinnatifid basal leaves that persist well beyond anthesis. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 365. | FNA vol. 7, p. 386. |
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 | Turritis laevigata, Arabis hastata, Arabis heterophylla, Arabis laevigata, Arabis lyrifolia |
Name authority | (Nuttall) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 64. (2006) | (Muhlenberg ex Willdenow) Al-Shehbaz: Novon 13: 386. (2003) |
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