Boechera collinsii |
Boechera suffrutescens |
|
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collin's suncress, Collins' rockcress |
woody rock-cress |
|
Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; long-lived; sexual or apomictic; caudex 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 branch, arising from center of rosette, elevated above ground surface on woody base, 1–4(–5) dm, usually glabrous proximally, rarely pubescent, trichomes short-stalked, 2-rayed, 0.1–0.3 mm, glabrous 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 narrowly oblanceolate, 1.5–6 mm wide, margins entire, not ciliate or, rarely, with simple trichomes to 0.7 mm, surfaces glabrous or sparsely to densely pubescent, trichomes short-stalked, 2–6-rayed, 0.07–0.4 mm. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
(4–)6–12, sometimes concealing stem proximally; blade auricles 0.5–2 mm, surfaces of distalmost leaves glabrous. |
Racemes | (15–)30–90-flowered, usually unbranched. |
6–12-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. |
pendent at anthesis; sepals glabrous; petals purple or whitish with rose tips, 4.5–6 × 2–2.5 mm, glabrous; pollen ellipsoid or spheroid. |
Fruiting pedicels | reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple. |
reflexed, usually abruptly recurved at base, otherwise straight, 4–18 mm, glabrous. |
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. |
reflexed to closely pendent, sometimes appressed to rachis, often secund, straight to somewhat curved, edges undulate (not parallel), 3–7(–8) cm × 3–5(–6) mm; valves glabrous; ovules 20–30 per ovary; style 0.4–1.2 mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
uniseriate, 2.5–5.5 × 1.8–3.5 mm; wing continuous, 0.8–1.5 mm wide. |
2n | = 14. |
|
Boechera collinsii |
Boechera suffrutescens |
|
Phenology | Flowering May–Jun. | Flowering Jun–Aug. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Rocky slopes and gravelly soil, often with sagebrush |
Elevation | 600-1400 m (2000-4600 ft) | 1800-3000 m (5900-9800 ft) |
Distribution |
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
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CA; ID; NV; OR; WA
|
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.) |
Boechera suffrutescens is recognizable by its prominently suffrutescent habit and wide (greater than 3 mm), reflexed fruits. Both sexual and apomictic collections are known; further study is needed to determine whether they truly are conspecific. The taxon previously known as Arabis suffrutescens var. horizontalis appears to be of hybrid origin; it is treated here as a distinct species (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. 370. | FNA vol. 7, p. 409. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii | Arabis suffrutescens, Arabis dianthifolia, Arabis duriuscula |
Name authority | (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) | (S. Watson) Dorn: Brittonia 55: 3. (2003) |
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