Boechera rollei |
Boechera xylopoda |
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Rolle's rock-cress |
beautiful rockcress, bigfoot hybrid rockcress |
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Habit | Perennials; long-lived; sexual; caudex woody. | Perennials; long-lived; apomictic; caudex woody. |
Stems | usually 1 per caudex branch, arising from center of rosette, elevated above ground surface on woody base, 1.5–2.5 dm, glabrous throughout. |
usually 1 from per caudex branch, arising from center of leaf tuft, elevated above ground surface on woody base, (3–)5–7.5 dm, pubescent proximally, trichomes short-stalked, 2–5-rayed, 0.25–0.9 mm., similarly pubescent distally. |
Basal leaves | blade oblanceolate, 3–8 mm wide, margins entire, ciliate proximally, trichomes (simple), 0.2–0.7 mm, surfaces glabrous or sparsely pubescent, trichomes short-stalked, 2–4-rayed, 0.2–0.4 mm. |
blade linear-oblanceolate to oblanceolate, 3–7 mm wide, margins entire or somewhat dentate, ciliate near petiole base, trichomes (simple), to 1.5 mm, surfaces densely pubescent, trichomes short-stalked, 4–8-rayed, 0.15–0.5 mm. |
Cauline leaves | 6–12, sometimes concealing stem proximally; blade auricles 0.5–2.5 mm, surfaces of distalmost leaves glabrous. |
8–18, usually not concealing stem; blade auricles 1–2 mm, surfaces of distalmost leaves sparsely pubescent. |
Racemes | 3–7-flowered, unbranched. |
20–38-flowered, usually unbranched. |
Flowers | divaricate-ascending at anthesis; sepals glabrous; petals creamy white, 8–11 × 2–2.5 mm, glabrous; pollen ellipsoid. |
divaricate to pendent at anthesis; sepals pubescent; petals purple, 9–12 × 2–3.5 mm, sparsely pubescent (often some trichomes abaxially); pollen spheroid. |
Fruiting pedicels | strongly curved proximally, 4–6 mm, glabrous. |
descending-divaricate, usually recurved, 9–20 mm, usually pubescent, rarely glabrous, trichomes subappressed, branched. |
Fruits | pendent, not appressed to rachis, not secund, straight to slightly curved, edges undulate (not parallel), 3.5–6 cm × 2.5–3.5 mm; valves glabrous; ovules 14–22 per ovary; style 0.5–1 mm. |
reflexed, not appressed to rachis, not secund, straight, edges parallel, 5–7 cm × 2–2.5 mm; valves glabrous proximally, sparsely pubescent distally; ovules 98–126 per ovary; style 0.1–0.5 mm. |
Seeds | uniseriate, 3–4 × 1.5–2 mm; wing distal and proximal, 0.3–0.6 mm wide. |
sub-biseriate, 2–2.5 × 1.3–1.6 mm; wing continuous, 0.2–0.25 mm wide. |
Boechera rollei |
Boechera xylopoda |
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Phenology | Flowering Aug. | Flowering Mar–May. |
Habitat | Peridotite rocks on sparsely forested slopes | Rock outcrops and gravelly slopes, often under shelter of shrubs in desert scrub, sagebrush, and chaparral communities |
Elevation | 1600-1800 m (5200-5900 ft) | 900-2000 m (3000-6600 ft) |
Distribution |
CA |
CA; NV
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Discussion | Boechera rollei is easily distinguished from the habitally similar B. suffrutescens by its longer (8–11 versus 4.5–6 mm) petals, narrower (2.5–3.5 versus 3–6 mm) fruits, and narrower (0.3–0.6 versus 0.8–1.5 mm) seed wings. This distinctive sexual species is known only from the vicinity of the type locality on the divide between the Applegate and Klamath Rivers in Siskiyou County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Although usually treated as a variety of Arabis (Boechera) pulchra, B. xylopoda is an apomictic taxon that is morphologically intermediate between B. perennans and B. pulchra (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison) and probably arose through hybridization between those two sexual diploids. Arabis trichopoda Greene (1908), not Turczaninow (1840) is an illegitimate name, sometimes found in synonymy with Boechera xylopoda. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 403. | FNA vol. 7, p. 411. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis rollei | Arabis pulchra var. gracilis, Arabis pulchra var. glabrescens, Arabis pulchra var. viridis, B. pulchra var. gracilis |
Name authority | (Rollins) Al-Shehbaz: Novon 13: 389. (2003) | Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 250. (2007) |
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