Boechera howellii |
Boechera repanda |
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Howell's flat-seed rock-cress, Howell's rockcress, pioneer rock-cress |
Greene's rockcress, Yosemite rockcress |
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Habit | Perennials; long-lived; sexual; caudex usually woody. | Perennials; short- to long-lived; sexual; caudex usually not woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 0.6–2(–3) dm, glabrous throughout. |
usually 1 per caudex branch, arising from center of rosette near ground surface, (1–)2–9 dm, densely pubescent proximally, trichomes short- to long-stalked, 2–6-rayed, 0.2–0.5 mm, rarely mixed with simple ones, to 1.5 mm, glabrous or sparsely pubescent distally. |
Basal leaves | blade narrowly oblanceolate, 1–7 mm wide, margins entire, ciliate proximally, trichomes (simple mixed with a few short-stalked, 2-rayed ones) 0.1–0.4 mm, surfaces glabrous. |
blade broadly oblanceolate to obovate, 7–25(–50) mm wide, margins usually repand to coarsely dentate, rarely entire, not ciliate, surfaces moderately to densely pubescent, trichomes short- to long-stalked, 3–6-rayed, 0.2–0.5 mm. |
Cauline leaves | 2–4, not concealing stem; blade auricles (0–)0.2–1 mm, surfaces of distalmost leaves usually glabrous, rarely ciliate proximally. |
(3–)8–30, not concealing stem; blade auricles absent, surfaces of distalmost leaves sparsely pubescent. |
Racemes | 2–5-flowered, unbranched. |
7–25-flowered, sometimes branched. |
Flowers | erect to ascending at anthesis; sepals glabrous; petals white to dark lavender, 4–8 × 1–2.5 mm, glabrous; pollen ellipsoid. |
erect to ascending at anthesis; sepals glabrous or sparsely pubescent; petals white, 3.5–6 × 0.8–1 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | ascending, straight, 4–10 mm, glabrous. |
erect to divaricate-ascending, straight, 3–10 mm, glabrous or pubescent, trichomes spreading, usually 2–5-rayed, rarely simple. |
Fruits | suberect to ascending, usually not appressed to rachis, not secund, straight to curved, edges often somewhat undulate (not parallel), 2.5–6.5 cm × 3–7 mm; valves glabrous; ovules 10–20 per ovary; style 0.05–0.3 mm. |
divaricate-ascending, not appressed to rachis, not secund, usually curved, rarely straight, edges parallel, (3.5–)5–13.5 cm × 2.5–4 mm; valves glabrous or pubescent throughout; ovules 34–50 per ovary; style 0.5–1.5 mm. |
Seeds | uniseriate, 3–6 × 2–4 mm; wing continuous, 1.3–2.5 mm wide. |
uniseriate, 2.5–5(–6) × 2–3(–3.5) mm; wing continuous, 0.7–1.8 mm wide. |
2n | = 14. |
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Boechera howellii |
Boechera repanda |
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Phenology | Flowering Jun–Aug. | Flowering Jun–Jul. |
Habitat | Rock outcrops, talus slopes and gravelly soil in alpine and subalpine habitats | Rock outcrops, talus, and gravelly soil in meadows and open pine forests |
Elevation | 1800-3800 m (5900-12500 ft) | 1600-3500 m (5200-11500 ft) |
Distribution |
CA; NV; OR
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CA; NV
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Discussion | Boechera howellii usually is subsumed under B. platysperma, but the two taxa are distinct (see M. D. Windham and I. A. Al-Shehbaz 2006 for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Boechera repanda is a sexual diploid that is distinguished from all other western North American species by its wide (10–50 mm), repand to coarsely dentate basal leaves. The form recognized as var. greenei appears to be a growth response to ecologically marginal habitats. Boechera repanda occurs sporadically in the Sierra Nevada and Transverse Ranges of California, and barely extends into the Carson Range in western Nevada. Arabis inamoena Greene (1911), not Greene (1908) is an illegitimate name, sometimes found in synonymy with Boechera repanda. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 384. | FNA vol. 7, p. 402. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis howellii, Arabis conferta, Arabis inamoena var. acutata, Arabis platyloba, Arabis platysperma var. howellii, Arabis platysperma var. imparata | Arabis repanda, Arabis repanda var. greenei |
Name authority | (S. Watson) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 69. (2006) | (S. Watson) Al-Shehbaz: Novon 13: 388. (2003) |
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