Boechera collinsii |
Boechera inyoensis |
|
---|---|---|
collin's suncress, Collins' rockcress |
Inyo rockcress |
|
Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; short-lived; apomictic; caudex usually not woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, (1.5–)2.5–8 dm, densely pubescent proximally, trichomes simple and short-stalked, 2-rayed, to 1 mm, sparsely pubescent or glabrous distally. |
usually 1 per caudex, arising from center of rosette near ground surface, (1–)2.5–6.5 dm, densely pubescent proximally, trichomes short-stalked, 7–12-rayed, 0.1–0.2 mm, densely to sparsely pubescent distally. |
Basal leaves | blade oblanceolate, 1–7 mm wide, margins entire or dentate, ciliate along petiole, trichomes (simple), to 0.7 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 5–8-rayed, 0.15–0.4 mm. |
blade oblanceolate, 1–4(–8) mm wide, margins entire, ciliate along petiole and proximally, trichomes (simple), to 1 mm, surfaces densely pubescent, trichomes short-stalked, 3–10-rayed, 0.2–0.7 mm. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
(7–)12–35, concealing stem proximally; blade auricles 0.5–2 mm, surfaces of distalmost leaves densely pubescent. |
Racemes | (15–)30–90-flowered, usually unbranched. |
10–65-flowered, usually unbranched. |
Flowers | descending to pendent at anthesis; sepals pubescent; petals usually white, rarely lavender, 4–6 × 0.8–1.5 mm, glabrous; pollen ellipsoid. |
ascending at anthesis; sepals pubescent; petals lavender to purplish, 5–8 × 1.2–2 mm, glabrous; pollen spheroid. |
Fruiting pedicels | reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple. |
divaricate-ascending to horizontal, straight or slightly curved downward, 5–15 mm, sparsely pubescent, trichomes appressed, branched. |
Fruits | strongly reflexed, usually appressed to rachis, rarely somewhat secund, straight, edges parallel, 3.5–6 cm × 0.9–1.5 mm; valves glabrous; ovules 70–126 per ovary; style 0.2–0.5 mm. |
divaricate-ascending to widely pendent, not appressed to rachis, not secund, usually curved, rarely straight, edges parallel, 3.7–6.5 cm × 1.5–2.2 mm; valves glabrous; ovules 74–134 per ovary; style 0.05–0.2 mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
usually sub-biseriate, rarely uniseriate, 1.7–2 × 1–1.5 mm; wing continuous, 0.1–0.2 mm wide. |
2n | = 14. |
= 21. |
Boechera collinsii |
Boechera inyoensis |
|
Phenology | Flowering May–Jun. | Flowering Apr–Jun. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Limestone and volcanic rock outcrops and clay soils in desert scrub and pinyon-juniper woodlands |
Elevation | 600-1400 m (2000-4600 ft) | 1400-2400 m (4600-7900 ft) |
Distribution |
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
|
CA; NV; UT
|
Discussion | Though often treated as a variety of Arabis (Boechera) holboellii (e.g., R. C. Rollins 1993; G. A. Mulligan 1996), B. collinsii is easily distinguished from that species by having simple and 2-rayed (versus 4–8-rayed) trichomes proximally on stems, and narrower (0.9–1.5 versus 2–2.5 mm) usually non-secund fruits. The two taxa also show allopatric distributions, with B. collinsii found on the North American continent (usually east of the Rocky Mountains) and B. holboellii apparently confined to Greenland. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Some plants here assigned to Boechera inyoensis were treated by R. C. Rollins (1993) and N. H. Holmgren (2005b) as Arabis (or B.) beckwithii. Closer examination of the type specimens of A. beckwithii reveals that they are conspecific with B. puberula, a sexual diploid widespread in the Great Basin of western North America. Boechera inyoensis is an apomictic triploid that clearly contains at least one genome derived from B. shockleyi (M. D. Windham and I. A. Al-Shehbaz 2007b); the other parent has not been determined. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 370. | FNA vol. 7, p. 385. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii | Arabis inyoensis, Arabis holboellii var. derensis, B. selbyi var. inyoensis |
Name authority | (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) | (Rollins) Al-Shehbaz: Novon 13: 386. (2003) |
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