Boechera villosa
Boechera retrofracta
dangling suncress, reflexed rock-cress, secund rock-cress
1–3 per caudex branch, arising laterally proximal to sterile shoots near ground surface, ca. 2.5 dm, densely pubescent proximally, trichomes simple and 2-rayed, 0.25–0.7 mm, glabrescent 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.
blade oblanceolate to obovate, 2.5–5 mm wide, margins entire, ciliate along petiole, trichomes (simple), to 1 mm, surfaces densely pubescent, trichomes simple and short-stalked, 2- or 3-rayed, 0.25–0.5 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.
4–6, not concealing stem;
blade auricles ca. 1 mm, surfaces of distalmost leaves sparsely pubescent.
15–40, concealing stem proximally;
blade auricles 0.5–2.5 mm or, rarely, absent, surfaces of distalmost leaves pubescent.
6–10-flowered, unbranched.
15–80(–140)-flowered, usually unbranched.
ascending at anthesis;
sepals pubescent;
petals lavender, 4–5 × 1–1.5 mm, glabrous;
pollen ellipsoid.
pendent at anthesis;
sepals pubescent;
petals white to lavender, 4–8 × 0.8–2.2 mm, glabrous;
pollen ellipsoid.
ascending, straight, 6–10 mm, glabrous or sparsely pubescent, trichomes subappressed, branched.
reflexed, abruptly recurved at base, otherwise usually straight, 7–12(–18) mm, pubescent, trichomes appressed, branched.
divaricate-ascending, not appressed to rachis, not secund, slightly curved, edges parallel, 4–5 cm × ca. 1 mm;
valves glabrous;
ovules ca. 64 per ovary;
style ca. 0.2 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.
uniseriate, (none mature).
uniseriate, 1–1.4 × 0.9–1.2 mm;
wing continuous, to 0.1 mm wide.
= 14.
Boechera villosa
Boechera retrofracta
Boechera villosa is known only from the type collection from the Rio Grande Gorge in Taos County. The holotype was originally identified as Arabis (Boechera) perennans but clearly is more closely related to B. pallidifolia (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.)
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