Boechera collinsii
Boechera shockleyi
collin's suncress, Collins' rockcress
Shockley's Rock cress
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, (0.8–)2–5 dm, densely pubescent proximally, trichomes short-stalked, 7–12-rayed, 0.1–0.2 mm, densely to sparsely pubescent distally.
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, 3–10 mm wide, margins entire, not ciliate, surfaces densely pubescent, trichomes short-stalked, 7–12-rayed, 0.1–0.2 mm.
(8–)15–40, concealing stem proximally;
blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent.
14–60, concealing stem for most of length;
blade auricles 0.5–4 mm, surfaces of distalmost leaves densely pubescent.
(15–)30–90-flowered, usually unbranched.
20–70-flowered, usually unbranched.
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 pubescent;
petals lavender, 6–9 × 0.8–1.2 mm, glabrous;
pollen ellipsoid.
reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple.
divaricate-ascending, straight, 7–28 mm, pubescent, trichomes appressed, branched.
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, not secund, usually curved, rarely straight, edges parallel, 4.5–11 cm × 1.5–2 mm;
valves glabrous or sparsely pubescent throughout;
ovules 140–190 per ovary;
style 0.05–0.6 mm.
uniseriate, 1–1.4 × 0.8–1 mm;
wing continuous (rarely absent), to 0.1 mm wide.
sub-biseriate, 1–1.3 × 0.7–0.8 mm;
wing distal or, rarely, absent, 0.05–0.1 mm wide.
= 14.
Boechera collinsii
Boechera shockleyi
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 shockleyi is a distinctive sexual species recognizable by the combination of strongly overlapping cauline leaves, a dense covering of minute, 7–12-rayed trichomes, and relatively long, curved, divaricate-ascending fruits with sub-biseriate seeds. It is most similar to B. inyoensis, but differs from that species in its narrower (0.8–1.2 versus 1.2–2 mm) petals, eciliate basal leaves with smaller (0.1–0.2 versus 0.2–0.7 mm) trichomes, greater number (140–190 versus 74–134) of ovules per ovary, and shorter (1–1.3 versus 1.7–2 mm) seeds with distal (versus continuous) wings.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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