Draba heilii |
Draba arabisans |
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rock Draba, rock whitlow-mustard |
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Habit | Perennials; (densely cespitose); caudex few-branched (compact, with persistent, thickened leaves); not scapose. | Perennials; (sometimes cespitose); caudex simple or branched; not scapose. |
Stems | unbranched or branched distally, 0.3–0.7 dm, glabrous throughout or, rarely, pilose, trichomes simple and stalked, 2-rayed, 0.2–0.5 mm. |
branched or unbranched, (0.5–)0.7–3(–4.5) dm, pubescent proximally, glabrous or pubescent distally, trichomes sessile (non-crisped), 4- or 5-rayed, stellate, or subpectinate, 0.07–0.4 mm. |
Basal leaves | (persistent, imbricate); rosulate; undifferentiated into blade and petiole (becoming indurate at base); blade linear-lanceolate, 0.5–0.8 cm × 1–1.5(–2) mm, margins entire, surfaces glabrous or, rarely, pilose with simple and stalked, 2-rayed trichomes, (margins ciliate with simple and, rarely, 2-rayed setiform trichomes, 0.5–1.3 mm, midvein prominent). |
rosulate; petiolate; petiole base and margin sparsely ciliate, (trichomes simple and 2-rayed, 0.2–0.8 mm); blade oblanceolate to spatulate or linear-oblanceolate, 1–3.8(–5) cm × 2–5(–8) mm, margins dentate or denticulate, surfaces pubescent with sessile, non-crisped, 4- or 5-rayed, stellate trichomes, 0.07–0.5mm, (some rays branched, appearing 2–12-rayed, midvein obscure abaxially). |
Cauline leaves | 6–8; sessile; blade linear-oblong, 0.5–0.8 cm × 1–2 mm (widest about base), margins entire, (ciliate). |
(2 or) 3–10(–13); sessile; blade ovate to oblong, margins dentate to subentire, surfaces pubescent as basal. |
Racemes | 10–26-flowered, ebracteate, elongated in fruit; rachis not flexuous, usually glabrous, rarely pubescent, (trichomes non-crisped, simple and 2-rayed). |
5–18(–25)-flowered, ebracteate, elongated in fruit; rachis not flexuous, glabrous or pubescent as stem. |
Flowers | sepals ovate, 1.7–2.7 mm, usually glabrous, rarely pilose, (trichomes simple); petals yellow, oblong-oblanceolate, 4–6 × 1.5–2 mm; anthers oblong, 0.5–0.6 mm. |
sepals oblong, 1.7–2.5 mm, pubescent, trichomes short-stalked, 3- or 4-rayed; petals white, broadly obovate, 3.5–5 × 1.5–2.5 mm; anthers ovate, 0.4–0.5 mm. |
Fruiting pedicels | ascending, straight, 3–5(–7) mm, usually glabrous, rarely pilose, (trichomes simple and 2-rayed, stalked). |
divaricate-ascending to suberect, straight or slightly curved, (3–)4–10(–13) mm, glabrous or pubescent as stem. |
Fruits | narrowly lanceolate, twisted 1/2 turn or plane, flattened, 7–10 × 1.3–1.6 mm; valves glabrous; ovules 16–20 per ovary; style 0.7–1.3 mm. |
ovate to lanceolate or linear-lanceolate, usually slightly twisted, rarely plane, flattened, 5–11(–14) × 2–3.5 mm; valves usually glabrous, rarely pubescent, trichomes 3- or 4-rayed, 0.07–0.2 mm; ovules 20–28(–32) per ovary; style (0.2–)0.4–1 mm. |
Seeds | ovoid, 1 × 0.6 mm. |
oblong, 0.8–1.1 × 0.6–0.8 mm. |
2n | = 96. |
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Draba heilii |
Draba arabisans |
|
Phenology | Flowering Jun–Jul. | Flowering Jun–Aug. |
Habitat | Alpine tundra | Rock outcrops and talus (usually limestone or dolomite), open woods, rocky shores |
Elevation | ca. 3700 m (ca. 12100 ft) | 0-300 m (0-1000 ft) |
Distribution |
NM |
ME; MI; MN; NY; VT; WI; MB; NB; NF; NS; ON; QC
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Discussion | Draba heilii is restricted to Mora and Rio Arriba counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Draba arabisans is often confused with D. glabella (2n = 80); it is easily distinguished by having sessile (versus short-stalked) stellate trichomes on abaxial leaf blade surfaces and longer styles (0.2–)0.4–1 [versus 0.1–0.2(–0.4)] mm. Both species have twisted and plane fruits; D. arabisans has mostly twisted fruits; D. glabella has predominantly plane fruits. The complete absence of simple trichomes proximally on stems of D. arabisans can be a useful feature separating it from D. glabella, which often has at least some simple trichomes on the proximal half of the stem. Draba arabis Persoon is an illegitimate name, sometimes found in synonymy with D. arabisans. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 311. | FNA vol. 7, p. 291. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | D. arabisans var. superiorensis, D. incana var. arabisans, D. incana var. glabriuscula | |
Name authority | Al-Shehbaz: Harvard Pap. Bot. 14: 83, fig. 1. (2009) | Michaux: Fl. Bor.-Amer. 2: 28. (1803) |
Web links |