Boechera atrorubens
Boechera glareosa
black-flower rockcress, dark-red-flower rockcress, purple sickle-pod rock-cress, sicklepod rockcress
usually 1 per caudex branch, arising from center of rosette near ground surface, 0.8–6 dm, sparsely pubescent proximally, trichomes short-stalked and simple, (scattered), 2-rayed, 0.1–0.15 mm, glabrous distally.
usually 2–6 per caudex branch, arising from margin of rosette near ground surface, 0.8–4 dm, densely pubescent proximally, trichomes simple and short-stalked, 2-rayed, 0.3–0.6 mm, glabrous distally.
blade oblanceolate, 4–10 mm wide, margins usually dentate, not ciliate, surfaces densely pubescent, trichomes short-stalked, 3- or 4-rayed, 0.1–0.2 mm.
blade narrowly oblanceolate, 1–5 mm wide, margins entire or few-toothed, ciliate proximally, trichomes (simple), to 0.9 mm, surfaces densely pubescent, trichomes simple and short-stalked, 2- or 3-rayed, 0.3–0.5 mm.
7–25, concealing stem proximally;
blade auricles 1–4 mm, surfaces of distalmost leaves glabrous.
3–6, not concealing stem;
blade auricles 0.3–0.6 mm, surfaces of distalmost leaves glabrous.
6–20-flowered, usually unbranched.
7–15-flowered, usually unbranched.
ascending at anthesis;
sepals pubescent;
petals dark reddish purple (drying indigo), 7–9 × 1.5–2 mm, glabrous;
pollen ellipsoid.
ascending at anthesis;
sepals pubescent;
petals lavender, 3.5–6 × 1–1.5 mm, glabrous;
pollen ellipsoid.
ascending, usually straight, 5–10 mm, glabrous or pubescent, trichomes spreading, simple.
divaricate-ascending to horizontal, straight or gently recurved, 4–10 mm, glabrous or sparsely pubescent, trichomes spreading.
ascending, not appressed to rachis, not secund, curved or straight, edges parallel, (4–)6–12 cm × 1.7–2.2 mm;
valves glabrous;
ovules 80–100 per ovary;
style 0.2–0.5 mm.
divaricate-ascending to horizontal, not appressed to rachis, not secund, usually curved or straight, edges parallel, 2.5–4 cm × 1.2–1.5 mm;
valves glabrous;
ovules 50–80 per ovary;
style 0.05–0.3 mm.
uniseriate, 1.2–1.7 × 0.9–1.2 mm;
wing lateral and distal, 0.1–0.2 mm wide.
uniseriate, 1–1.5 × 0.7–1 mm;
wing usually distal, ca. 0.1 mm wide.
Boechera atrorubens
Boechera glareosa
Boechera atrorubens is often treated as a variety of B. sparsiflora (e.g., R. C. Rollins 1993), it is readily separated from that species by having proximal stems sparsely (versus densely) pubescent with much smaller (0.15 versus 1.5 mm) trichomes. The two taxa rarely grow in proximity and, in areas where they are sympatric, B. atrorubens is further distinguished by its narrower (1.5–2 versus 2–5 mm) petals that are dark reddish purple to indigo (versus lavender or white).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Specimens of Boechera glareosa originally were identified as Arabis microphylla var. macounii (= B. macounii) by R. C. Rollins. The former (a sexual species) is distinguished from the latter (an apomictic hybrid) by having wider (1–2 versus 0.5–0.8 mm) petals, fewer (2–9 versus mostly 9–16) cauline leaves, and fewer (7–15 versus 10–33) flowers per inflorescence. Boechera glareosa is known only from Moffat County, Colorado, and Summit and Uintah counties, Utah.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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