Boechera lasiocarpa |
Boechera retrofracta |
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dangling suncress, reflexed rock-cress, secund rock-cress |
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Habit | Perennials; long-lived; sexual; caudex often woody. | Biennials or perennials; short-lived; sexual; caudex present or absent. |
Stems | 1 or few per caudex branch, arising from center or margin of rosette, somewhat elevated on woody base or near ground surface, (0.7–)2–3.5 dm, densely pubescent proximally, trichomes short-stalked, 4–8-rayed, 0.05–0.15 mm, moderately to 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, 2–5 mm wide, margins entire, not ciliate, surfaces densely pubescent, trichomes short-stalked, 4–8-rayed, 0.05–0.15 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 | 4–10, often concealing stem proximally; blade auricles absent, surfaces of distalmost leaves sparsely to moderately pubescent. |
15–40, concealing stem proximally; blade auricles 0.5–2.5 mm or, rarely, absent, surfaces of distalmost leaves pubescent. |
Racemes | 5–12-flowered, usually unbranched. |
15–80(–140)-flowered, usually unbranched. |
Flowers | divaricate at anthesis; sepals pubescent; petals purple to lavender, 6–10 × 1.5–2.5 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 | descending, recurved, 4–14 mm, pubescent, trichomes appressed, branched. |
reflexed, abruptly recurved at base, otherwise usually straight, 7–12(–18) mm, pubescent, trichomes appressed, branched. |
Fruits | pendent, usually not appressed to rachis, rarely secund, straight or curved, 2–5 cm × 1.7–2.2 mm; valves glabrous or pubescent throughout; ovules 26–36 per ovary; style 0.2–0.9 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, 1.5–2 × 1–1.5 mm; wing distal or continuous, 0.1–0.2 mm wide. |
uniseriate, 1–1.4 × 0.9–1.2 mm; wing continuous, to 0.1 mm wide. |
2n | = 14. |
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Boechera lasiocarpa |
Boechera retrofracta |
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Phenology | Flowering May–Jun. | Flowering Apr–Aug. |
Habitat | Rocky ridges and slopes with dwarf sagebrush | Rock outcrops, open hillsides, gravel bars and sandy banks in grassland, sagebrush, oak woodlands, and open conifer forests |
Elevation | 1800-2800 m (5900-9200 ft) | 300-3300 m (1000-10800 ft) |
Distribution |
UT |
AK; CA; ID; MI; MT; NV; OR; UT; WA; WY; AB; BC; MB; NT; ON; QC; SK
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Discussion | Boechera lasiocarpa is a sexual species that appears to be restricted to the Bear River Mountains and northern Wasatch Range in north-central Utah. Reports of Arabis (Boechera) lasiocarpa from central Idaho (e.g., R. C. Rollins 1993; N. H. Holmgren 2005b) represent B. rollinsiorum (see M. D. Windham and I. A. Al-Shehbaz 2006 for detailed comparison). (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. 387. | FNA vol. 7, p. 402. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis lasiocarpa | 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 | (Rollins) Dorn: Brittonia 55: 3. (2003) | (Graham) Á. Löve & D. Löve: Taxon 31: 125. (1982) |
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