Boechera collinsii |
Boechera porphyrea |
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collin's suncress, Collins' rockcress |
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Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; usually long-lived; apomictic; caudex often 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. |
1 to several per caudex branch, arising from center of rosette or arising laterally proximal to sterile shoots, somewhat elevated on woody base or from ground surface, 2–5(–9) dm, usually glabrous proximally, rarely sparsely pubescent, trichomes simple and short-stalked, 2- or 3-rayed, 0.1–0.5 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 oblanceolate, (3–)5–15 mm wide, margins dentate, ciliate at least along petiole, trichomes to 1 mm, surfaces pubescent, trichomes short-stalked, 2–6-rayed, 0.1–0.5 mm. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
5–17(–21), sometimes concealing stem proximally; blade auricles 0.5–3.5(–5.5) mm, surfaces of distalmost leaves glabrous. |
Racemes | (15–)30–90-flowered, usually unbranched. |
10–30(–70)-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 glabrous; petals lavender, 6.5–8.5 × 1–2.5 mm, glabrous; pollen spheroid. |
Fruiting pedicels | reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple. |
horizontal, gently curved downward, 10–27 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. |
widely pendent, not appressed to rachis, not secund, usually curved, edges parallel, 3–7 cm × 1.8–2.5 mm; valves glabrous; ovules 100–160 per ovary; style 0.2–0.5 mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
sub-biseriate, 1.1–1.6 × 0.9–1.1 mm; wing continuous, 0.1–0.2 mm wide. |
2n | = 14. |
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Boechera collinsii |
Boechera porphyrea |
|
Phenology | Flowering May–Jun. | Flowering late Mar-early May. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Rocky slopes in evergreen woodlands or desert scrub |
Elevation | 600-1400 m (2000-4600 ft) | 1200-2100 m (3900-6900 ft) |
Distribution |
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
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NM; TX |
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.) |
Morphological evidence suggests that Boechera porphyrea is an apomictic species that arose through hybridization between B. texana and B. perennans (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. 398. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii | Arabis porphyrea |
Name authority | (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) | (Wooton & Standley) Windham: Harvard Pap. Bot. 11: 272. (2007) |
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