Boechera rollei |
Boechera macounii |
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Rolle's rock-cress |
littleleaf suncress, Macoun's suncress, sloppy suncress |
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Habit | Perennials; long-lived; sexual; caudex woody. | Perennials; usually long-lived; apomictic; caudex often 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. |
1 or several per caudex branch, arising from center or margin of rosette near ground surface, 2–3.6 dm, densely pubescent proximally, trichomes simple and short-stalked, 2-rayed, 0.1–0.8 mm, glabrous 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 oblanceolate to linear-oblanceolate, 1–3(–5) mm wide, margins entire or minutely toothed, ciliate proximally, trichomes (simple), to 0.7 mm, surfaces densely pubescent, trichomes short-stalked, 3–6-rayed, 0.07–0.3 mm. |
Cauline leaves | 6–12, sometimes concealing stem proximally; blade auricles 0.5–2.5 mm, surfaces of distalmost leaves glabrous. |
(5–)9–16, often concealing stem proximally; blade auricles 0.5–1.5 mm, surfaces of distalmost leaves glabrous. |
Racemes | 3–7-flowered, unbranched. |
10–33-flowered, usually unbranched. |
Flowers | divaricate-ascending at anthesis; sepals glabrous; petals creamy white, 8–11 × 2–2.5 mm, glabrous; pollen ellipsoid. |
divaricate-ascending at anthesis; sepals pubescent; petals lavender to purple, 4–5 × 0.5–0.8 mm, glabrous; pollen spheroid. |
Fruiting pedicels | strongly curved proximally, 4–6 mm, glabrous. |
divaricate-ascending to horizontal, straight, 5–13(–17) mm, usually densely pubescent, rarely glabrous, trichomes appressed, 2- or 3-rayed. |
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. |
divaricate-ascending to descending, not appressed to rachis, not secund, usually curved, edges parallel, 3.5–6.5 cm × 0.8–1.2 mm; valves glabrous; ovules 56–78 per ovary; style 0.1–0.4 mm. |
Seeds | uniseriate, 3–4 × 1.5–2 mm; wing distal and proximal, 0.3–0.6 mm wide. |
uniseriate, 1–1.2 × 0.7–1 mm; wing often continuous, 0.05–0.15 mm wide. |
Boechera rollei |
Boechera macounii |
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Phenology | Flowering Aug. | Flowering May–Jul. |
Habitat | Peridotite rocks on sparsely forested slopes | Rocky hillsides in open pinewoods |
Elevation | 1600-1800 m (5200-5900 ft) | 2200-2900 m (7200-9500 ft) |
Distribution |
CA |
ID; MT; WY; BC |
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.) |
Morphological evidence suggests that Boechera macounii is an apomictic species that arose through hybridization between B. collinsii and B. microphylla (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. 403. | FNA vol. 7, p. 389. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis rollei | Arabis macounii, Arabis densicaulis, Arabis microphylla var. macounii |
Name authority | (Rollins) Al-Shehbaz: Novon 13: 389. (2003) | (S. Watson) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 267. (2007) |
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