Boechera collinsii |
Boechera laevigata |
|
---|---|---|
collin's suncress, Collins' rockcress |
smooth rockcress |
|
Habit | Perennials; usually short-lived; sexual; caudex not woody. | Biennials; short-lived; sexual; caudex not evident. |
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 per plant, arising from center of rosette near ground surface, (1.5–)3–11 dm, glabrous throughout. |
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 obovate to oblanceolate, (4–)10–40 mm wide, margins serrate or dentate, ciliate-mucronate on teeth, trichomes often minute, surfaces glabrous or sparsely pubescent, trichomes simple, 0.1–0.6 mm. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
7–15, often concealing stem proximally; blade auricles 3–12(–17) mm, surfaces of distalmost leaves glabrous. |
Racemes | (15–)30–90-flowered, usually unbranched. |
16–45-flowered, sometimes branched. |
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 white, 3–5 × 1–1.5 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple. |
suberect to divaricate-ascending, straight to slightly curved, 5–23 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. |
divaricate-ascending, not appressed to rachis, rarely somewhat secund, curved, edges parallel, (4–)6–11.7 cm × 1–2 mm; valves glabrous; ovules 50–80 per ovary; style 0.1–0.7(–1) mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
uniseriate, 1.2–2.2 × 0.8–1.4 mm; wing continuous, 0.1–0.3 mm wide distally. |
2n | = 14. |
= 14. |
Boechera collinsii |
Boechera laevigata |
|
Phenology | Flowering May–Jun. | Flowering Mar–May. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Rocky bluffs, cedar glades, wooded hillsides, floodplains |
Elevation | 600-1400 m (2000-4600 ft) | 100-500 m (300-1600 ft) |
Distribution |
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
|
AL; AR; CT; DC; DE; GA; IA; IL; IN; KY; MA; MD; MI; MO; NC; NH; NJ; NY; OH; OK; PA; SC; TN; VA; VT; WI; WV; ON; QC |
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.) |
The taxon sometimes treated as Arabis laevigata var. missouriensis is here recognized as a separate species (Boechera missouriensis) based on its significantly longer petals (5–10 versus 3–5 mm) and distinctive, lyrate-pinnatifid basal leaves that persist well beyond anthesis. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 370. | FNA vol. 7, p. 386. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii | Turritis laevigata, Arabis hastata, Arabis heterophylla, Arabis laevigata, Arabis lyrifolia |
Name authority | (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) | (Muhlenberg ex Willdenow) Al-Shehbaz: Novon 13: 386. (2003) |
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