Boechera collinsii |
Boechera pratincola |
|
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collin's suncress, Collins' rockcress |
meadow rock-cress |
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Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; usually short-lived; apomictic; caudex 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 branch, arising from center of rosette near ground surface, 2–6 dm, pubescent proximally, trichomes sessile, 2- or 3-rayed, 0.15–0.6 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, 1.5–5(–7) mm wide, margins usually entire, rarely denticulate, ciliate at petiole base, trichomes to 0.4 mm, surfaces pubescent, trichomes sessile, 2–4(–6)-rayed, 0.1–0.45 mm. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
(7–)13–42, concealing stem proximally; blade auricles 1–4 mm, surfaces of distalmost leaves sparsely pubescent apically. |
Racemes | (15–)30–90-flowered, usually unbranched. |
(7–)14–45-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, 6–10 × 1.5–2 mm, glabrous; pollen spheroid. |
Fruiting pedicels | reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple. |
erect, straight, 5–12 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. |
erect, appressed to rachis, not secund, straight, edges parallel, 4–6.5 cm × 1.5–2 mm; valves glabrous; ovules 60–140 per ovary; style 0.1–0.3 mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
sub-biseriate, 1.4–2 × 1–1.4 mm; wing continuous, 0.1–0.35 mm wide. |
2n | = 14. |
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Boechera collinsii |
Boechera pratincola |
|
Phenology | Flowering May–Jun. | Flowering Jun–Aug. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Rocky slopes and soil patches in open areas and along forest edges |
Elevation | 600-1400 m (2000-4600 ft) | 1900-3200 m (6200-10500 ft) |
Distribution |
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
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CA; ID; NV; OR
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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 pratincola is an apomictic species that arose through hybridization between B. paupercula and B. stricta (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 370. | FNA vol. 7, p. 399. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii | Arabis pratincola, Arabis drummondii var. pratincola, Arabis nemophila |
Name authority | (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) | (Greene) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 245. (2007) |
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