Boechera cascadensis |
Boechera falcifructa |
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Cascade rock-cress, Cascade suncress, Cascades rockcress, littleleaf rockcress |
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Habit | Perennials; long-lived; (cespitose); apomictic; caudex somewhat woody. | Perennials; usually long-lived; apomictic; caudex often woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 0.5–2.2 dm, sparsely pubescent proximally, trichomes simple and short-stalked, 2- or 3-rayed, 0.1–0.2 mm, glabrous distally. |
usually 1 per caudex branch, arising from center of rosette near ground surface, 1.5–4.5 dm, densely pubescent proximally, trichomes short-stalked, 4–9-rayed, 0.05–0.2 mm, glabrous or sparsely pubescent distally. |
Basal leaves | blade linear-oblanceolate, 0.7–2 mm wide, margins entire, ciliate proximally, trichomes to 0.4 mm, surfaces densely pubescent, trichomes short-stalked, (2- or) 3–6-rayed, 0.05–0.2(–0.3) mm. |
blade linear to narrowly oblanceolate, 1–4 mm wide, margins entire, ciliate at petiole base, trichomes (simple), to 0.5 mm, surfaces densely pubescent, trichomes short-stalked, 4–9-rayed, 0.05–0.2 mm. |
Cauline leaves | 4–6, not concealing stem; blade auricles 0.5–1 mm, surfaces of distalmost leaves glabrous. |
5–9, not concealing stem; blade auricles 0.5–1 mm, surfaces of distalmost leaves sparsely pubescent. |
Racemes | 3–11-flowered, unbranched. |
10–18-flowered, sparingly branched. |
Flowers | ascending at anthesis; sepals glabrous or sparsely pubescent; petals lavender, 5–6 × 1–1.7 mm, glabrous; pollen spheroid. |
divaricate-ascending at anthesis; sepals pubescent; petals lavender, 5–7 × 0.7–1.2 mm, glabrous; pollen spheroid. |
Fruiting pedicels | ascending to divaricate-ascending, straight, 3–8 mm, glabrous. |
divaricate-descending, gently curved downward, 6–12 mm, pubescent, trichomes appressed, branched. |
Fruits | ascending to divaricate-ascending, not appressed to rachis, not secund, straight, edges parallel, 3.5–6.2 cm × 1.2–1.5 mm; valves glabrous; ovules 58–80 per ovary; style 0.8–1.5 mm. |
divaricate-descending, not appressed to rachis, not secund, gently curved, edges parallel, 4.5–6 cm × 1.2–1.5 mm; valves glabrous; ovules 62–80 per ovary; style 0.5–1 mm. |
Seeds | uniseriate, 1.1–1.3 × 0.9–1 mm; wing continuous, 0.05–0.1 mm wide. |
uniseriate, 1.2–1.7 × 0.8–1.2 mm; wing mostly distal, 0.05–0.1 mm wide. |
Boechera cascadensis |
Boechera falcifructa |
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Phenology | Flowering Jun. | Flowering May–Jun. |
Habitat | Basaltic cliffs and rocky slopes in subalpine areas | Rocky slopes and sandy soil in sagebrush or pinyon-juniper woodlands |
Elevation | ca. 1900 m (ca. 6200 ft) | 1500-1800 m (4900-5900 ft) |
Distribution |
OR; WA |
NV |
Discussion | Of conservation concern. Morphological evidence suggests that Boechera cascadensis is an apomictic species that arose through hybridization between B. microphylla and B. paupercula (see M. D. Windham and I. A. Al-Shehbaz 2007 for detailed comparison). It is known from two collections: the type specimens from Kittitas County, Washington, and a more recent collection from Baker County, Oregon. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Morphological evidence suggests that Boechera falcifructa is an apomictic species that arose through hybridization between B. cobrensis and B. fernaldiana. It is more similar to the former, but is distinguished by its gently curved fruiting pedicels (versus strongly recurved or reflexed distally), narrower (1.2–1.5 versus 1.7–2.5 mm) fruits, more (62–80 versus 34–64) ovules per ovary, longer (0.5–1 versus 0.05–0.2 mm) styles, and narrower (0.05–0.1 versus 0.25–0.5 mm) seed wings. Although independently reproducing, B. falcifructa is known only from Elko and Lander counties, where the parental species grow in proximity. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 369. | FNA vol. 7, p. 377. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis microphylla var. thompsonii | Arabis falcifructa |
Name authority | Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 260. (2007) | (Rollins) Al-Shehbaz: Novon 13: 385. (2003) |
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