Boechera oxylobula |
Boechera cobrensis |
|
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cobre rock-cress, Masonic rock-cress, sagebrush rockcress |
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Habit | Perennials; short- to long-lived; (cespitose); sexual; caudex usually not woody. | Perennials; long-lived; (often cespitose); sexual; caudex somewhat woody (usually without persistent leaf bases). |
Stems | usually 3–7 per caudex branch, arising from margin of rosette near ground surface, or arising laterally proximal to sterile shoots, 0.4–2.5 dm, glabrous or pubescent proximally, trichomes simple and short-stalked, 2-rayed, 0.1–0.4 mm, glabrous distally. |
usually 1 per caudex branch, arising from center of rosette near ground surface, (1.2–)2.5–6 dm, densely pubescent proximally, trichomes short-stalked, 4–10-rayed, 0.1–0.2 mm, sparsely pubescent or glabrous distally. |
Basal leaves | blade linear to linear-oblanceolate, 1–2.5 mm wide, margins usually entire, rarely denticulate, often ciliate, trichomes (simple), 0.3–0.7 mm, surfaces glabrous or sparsely pubescent, trichomes short-stalked, 2- or 3-rayed, 0.1–0.4 mm. |
blade linear to narrowly oblanceolate, 1–4 mm wide, margins entire, ciliate near petiole base, trichomes (simple), to 0.6 mm, surfaces densely pubescent, trichomes short-stalked, 4–10-rayed, 0.1–0.2 mm. |
Cauline leaves | 3–12, not concealing stem; blade auricles absent, surfaces of distalmost leaves usually glabrous, rarely sparsely pubescent. |
5–10, not concealing stem; blade auricles 1–1.5 mm, surfaces of distalmost leaves usually sparsely pubescent. |
Racemes | 2–12-flowered, unbranched. |
10–25-flowered, often sparingly branched. |
Flowers | ascending-divaricate at anthesis; sepals glabrous or pubescent; petals white to pale lavender, 4–5 × 1.5–2 mm, glabrous; pollen ellipsoid. |
divaricate-ascending at anthesis; sepals pubescent; petals white to lavender, 3.5–6 × 0.7–1 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | divaricate-ascending to horizontal, slightly to strongly recurved, 3–8 mm, glabrous or sparsely pubescent, trichomes (isolated), simple. |
divaricate-ascending to horizontal, often straight proximally, usually strongly recurved or reflexed distally, 4–17 mm, usually pubescent, rarely glabrous, trichomes appressed, branched. |
Fruits | pendent, not appressed to rachis, not or, rarely, weakly secund, straight, edges parallel, 1.5–3.5 cm × 1.2–2 mm; valves glabrous; ovules 28–44 per ovary; style 0.1–0.4 mm. |
pendent, not appressed to rachis, not secund, straight or slightly curved, edges parallel, 2.5–5.5 cm × 1.7–2.5 mm; valves glabrous; ovules 34–64 per ovary; style 0.05–0.2 mm. |
Seeds | uniseriate, 0.9–1.2 × 0.6–1 mm; wing often continuous, 0.07–0.1 mm wide. |
uniseriate, 1.4–1.8 × 1–1.2 mm; wing continuous, 0.25–0.5 mm wide. |
2n | = 14. |
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Boechera oxylobula |
Boechera cobrensis |
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Phenology | Flowering May–Jul. | Flowering May–Jun. |
Habitat | Cliffs, rocky slopes, gravelly soil in sagebrush and open conifer forests | Sandy soil, usually under shelter of shrubs in semi-desert communities |
Elevation | 2100-3600 m (6900-11800 ft) | 1200-2800 m (3900-9200 ft) |
Distribution |
CO |
CA; ID; NV; OR; WY
|
Discussion | Most of the collections assigned here have been called Arabis (Boechera) demissa by other authors (e.g., R. C. Rollins 1993; N. H. Holmgren 2005b). Because the holotype of A. demissa is identical to B. oxylobula in nearly every way (see M. D. Windham and I. A. Al-Shehbaz 2006 for detailed comparison), we treat them as conspecific. Boechera oxylobula is restricted to Garfield, Gunnison, Hinsdale, Lake, Mineral, Park, and Saguache counties in central Colorado. The taxon traditionally treated as A. (Boechera) demissa var. languida is here recognized as an apomictic species of hybrid origin (see Windham and Al-Shehbaz 2007b for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Boechera cobrensis is a sexual diploid commonly found on stabilized sand dunes. The related B. lignifera often is found in similar habitats, and the two species can be difficult to distinguish where their ranges overlap in Idaho and Wyoming. It is possible that B. cobrensis was involved in the origin of some apomictic populations currently assigned to B. lignifera. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 391. | FNA vol. 7, p. 370. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis oxylobula, Arabis aprica, Arabis demissa, Arabis rugocarpa, B. demissa | Arabis cobrensis |
Name authority | (Greene) W. A. Weber: Phytologia 51: 370. (1982) | (M. E. Jones) Dorn: Vasc. Pl. Wyoming ed. 3, 375. (2001) |
Web links |