Boechera cobrensis |
Boechera pinetorum |
|
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cobre rock-cress, Masonic rock-cress, sagebrush rockcress |
Holboell's rock-cress, woodland rock-cress |
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Habit | Perennials; long-lived; (often cespitose); sexual; caudex somewhat woody (usually without persistent leaf bases). | Perennials; short-lived; apomictic; caudex not woody. |
Stems | 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. |
usually 1 per caudex branch, arising from center of rosette near ground surface, 2–8(–9.6) dm, densely pubescent proximally, trichomes simple and short-stalked, 2–4-rayed, to 1 mm, sparsely pubescent or glabrous distally. |
Basal leaves | 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. |
blade oblanceolate, 2–8(–11) mm wide, margins entire or denticulate, ciliate proximally, trichomes (simple), 0.5–1 mm, surfaces sparsely to densely pubescent, trichomes short-stalked, 2–4 (or 5)-rayed, 0.2–0.5 mm, these mixed with fewer simple ones. |
Cauline leaves | 5–10, not concealing stem; blade auricles 1–1.5 mm, surfaces of distalmost leaves usually sparsely pubescent. |
7–33, often concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves sparsely pubescent or glabrous. |
Racemes | 10–25-flowered, often sparingly branched. |
15–63-flowered, usually unbranched. |
Flowers | divaricate-ascending at anthesis; sepals pubescent; petals white to lavender, 3.5–6 × 0.7–1 mm, glabrous; pollen ellipsoid. |
divaricate to pendent at anthesis; sepals pubescent; petals white to lavender, 5–6 × 1–1.5 mm, glabrous; pollen spheroid. |
Fruiting pedicels | divaricate-ascending to horizontal, often straight proximally, usually strongly recurved or reflexed distally, 4–17 mm, usually pubescent, rarely glabrous, trichomes appressed, branched. |
reflexed, abruptly recurved near base, otherwise straight, 4–12 mm, sparsely pubescent or glabrous, trichomes spreading, simple and 2-rayed. |
Fruits | 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. |
reflexed to closely pendent, not appressed to rachis, not secund, straight or curved, edges parallel, (4.5–)5.5–8.5 cm × 1.5–2 mm; valves glabrous; ovules 70–110 per ovary; style 0.05–0.4 mm. |
Seeds | uniseriate, 1.4–1.8 × 1–1.2 mm; wing continuous, 0.25–0.5 mm wide. |
uniseriate, 1.5–1.8 × 1.2–1.5 mm; wing continuous, 0.15–0.3 mm wide. |
2n | = 14. |
|
Boechera cobrensis |
Boechera pinetorum |
|
Phenology | Flowering May–Jun. | Flowering May–Jul. |
Habitat | Sandy soil, usually under shelter of shrubs in semi-desert communities | Rock outcrops and gravelly soil in meadows and open conifer forests |
Elevation | 1200-2800 m (3900-9200 ft) | 1100-3200 m (3600-10500 ft) |
Distribution |
CA; ID; NV; OR; WY
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CA; NV; OR
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Discussion | 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.) |
Most authors (e.g., R. C. Rollins 1993; R. D. Dorn 2001; S. L. Welsh et al. 2003; N. H. Holmgren 2005b) have treated Boechera pinetorum as a variety of Arabis (Boechera) holboellii. Under this guise, the name has been applied to a vast array of plants collected throughout western North America. This includes a diversity of sexual diploids plus nearly every hybrid containing a genome from B. retrofracta. Based on re-examination of the type collection, we have adopted a much narrower concept of the species. Morphological evidence suggests that B. pinetorum is an apomictic triploid hybrid containing three different genomes, derived from B. rectissima, B. retrofracta, and B. sparsiflora. Plants closely resembling the type of B. pinetorum are confined to the northern Sierra Nevada and adjacent southern Cascades. The majority of collections previously associated with the epithet pinetorum represent B. pauciflora (see M. D. Windham and I. A. Al-Shehbaz 2007 for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 370. | FNA vol. 7, p. 397. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis cobrensis | Arabis pinetorum, Arabis divaricarpa var. pinetorum, Arabis holboellii var. pinetorum, B. holboellii var. pinetorum |
Name authority | (M. E. Jones) Dorn: Vasc. Pl. Wyoming ed. 3, 375. (2001) | (Tidestrom) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 271. (2007) |
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