Boechera subpinnatifida |
Boechera retrofracta |
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ashy rock-cress, Klamath rockcress |
dangling suncress, reflexed rock-cress, secund rock-cress |
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Habit | Perennials; long-lived; sexual; caudex woody (often with persistent, crowded leaf bases). | Biennials or perennials; short-lived; sexual; caudex present or absent. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 1–4(–5) dm, densely pubescent proximally, trichomes short-stalked, 2–6-rayed, 0.1–0.2 mm, sparsely pubescent distally. |
usually 1 per caudex branch, arising from center of rosette near ground surface, 1.5–7(–10.5) dm, densely pubescent proximally, trichomes short-stalked, 2–8-rayed, 0.1–0.2 mm, sparsely pubescent distally. |
Basal leaves | blade narrowly oblanceolate, 1–4(–5) mm wide, margins prominently dentate to subpinnatifid (leaf margins of sterile shoots often entire), ciliate near petiole base, trichomes (simple or 2-rayed), 0.4–0.6 mm, surfaces densely pubescent, trichomes short-stalked, (2–)4–9-rayed, 0.05–0.2 mm. |
blade oblanceolate, 2–7 mm wide, margins entire or shallowly dentate, sometimes ciliate at petiole base, surfaces densely pubescent, trichomes short-stalked, 5–10-rayed, 0.05–0.2 mm. |
Cauline leaves | (10–)20–60, often concealing stem throughout; blade auricles 0.5–3 mm, surfaces of distalmost leaves moderately to sparsely pubescent. |
15–40, concealing stem proximally; blade auricles 0.5–2.5 mm or, rarely, absent, surfaces of distalmost leaves pubescent. |
Racemes | 8–30-flowered, usually unbranched. |
15–80(–140)-flowered, usually unbranched. |
Flowers | divaricate-ascending to pendent at anthesis; sepals pubescent; petals usually purple, rarely lavender, 9–14 × 1.5–3 mm, glabrous; pollen ellipsoid. |
pendent at anthesis; sepals pubescent; petals white to lavender, 4–8 × 0.8–2.2 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | reflexed, strongly recurved, 5–15 mm, pubescent, trichomes appressed, branched. |
reflexed, abruptly recurved at base, otherwise usually straight, 7–12(–18) mm, pubescent, trichomes appressed, branched. |
Fruits | pendent, not appressed to rachis, not secund, straight to slightly curved, edges parallel, (3.5–)5–8 cm × (1.6–)2–3 mm; valves pubescent throughout; ovules 24–42 per ovary; style 0.5–1 mm. |
strongly reflexed, usually appressed to rachis, sometimes somewhat secund, straight, edges parallel, 3.5–9 cm × 0.9–1.8 mm; valves glabrous or sparsely pubescent throughout; ovules 60–116 per ovary; style 0.5–2 mm. |
Seeds | uniseriate, 2.5–3.5 × 1.5–2.2 mm; wing continuous or at both ends, 0.4–0.8 mm wide. |
uniseriate, 1–1.4 × 0.9–1.2 mm; wing continuous, to 0.1 mm wide. |
2n | = 14. |
= 14. |
Boechera subpinnatifida |
Boechera retrofracta |
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Phenology | Flowering Mar–May. | Flowering Apr–Aug. |
Habitat | Rock outcrops, talus, gravelly soil, often in sagebrush-grassland communities | Rock outcrops, open hillsides, gravel bars and sandy banks in grassland, sagebrush, oak woodlands, and open conifer forests |
Elevation | 800-2400 m (2600-7900 ft) | 300-3300 m (1000-10800 ft) |
Distribution |
CA; ID; NV; OR; UT
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AK; CA; ID; MI; MT; NV; OR; UT; WA; WY; AB; BC; MB; NT; ON; QC; SK
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Discussion | Originally thought to be restricted to northern California and adjacent Oregon, Boechera subpinnatifida is a sexual species that recently has been found in central Idaho, northern Nevada, and northwestern Utah. It appears to intergrade with both B. puberula and B. retrofracta, and species boundaries within this complex need further study. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Though often treated as a variety of Arabis (Boechera) holboellii (e.g., R. C. Rollins 1993; G. A. Mulligan 1996; N. H. Holmgren 2005b), B. retrofracta is easily distinguished from that species by having narrower (0.9–1.8 versus 2–2.5 mm), mostly non-secund fruits that are almost always appressed to rachises. The two taxa have allopatric distributions, with B. retrofracta found on the North American continent (mostly west of the Great Plains) and B. holboellii apparently confined to Greenland. Boechera retrofracta has formed hybrids with at least 12 other species. Besides differing in macromorphological characters, all those hybrids are distinct from B. retrofracta in the strict sense in having wider (20–30 versus 13–16 µm), spheroid pollen grains with asymmetric colpi. Arabis kochii Blankinship is an illegitimate name, sometimes found in synonymy with Boechera retrofracta. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 409. | FNA vol. 7, p. 402. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis subpinnatifida | Arabis retrofracta, Arabis arcuata var. secunda, Arabis exilis, Arabis holboellii var. retrofracta, Arabis holboellii var. secunda, Arabis lignipes, Arabis retrofracta var. multicaulis, Arabis secunda, Arabis sparsiflora subsp. secunda, Arabis tenuis, B. exilis, B. holboellii var. secunda |
Name authority | (S. Watson) Al-Shehbaz: Novon 13: 389. (2003) | (Graham) Á. Löve & D. Löve: Taxon 31: 125. (1982) |
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