Draba incerta |
Draba cusickii |
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whitlow-wort, Yellowstone Draba, Yellowstone Draba whitlow-wort, Yellowstone whitlow-grass, Yellowstone whitlow-wort |
Cusick's Draba, Steens Mountain whitlow-grass |
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Habit | Perennials; (cespitose, often pulvinate); caudex branched (dense with persistent leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Perennials; (loosely cespitose); caudex branched (with few, persistent leaf remains); scapose. |
Stems | unbranched, (0.2–)0.4–1.4(–2.1) dm, often pubescent throughout, sometimes glabrous distally, trichomes often simple and 2–5-rayed, 0.1–0.5 mm, (sometimes with mostly subpectinate ones). |
unbranched, 0.3–1.2 dm, pubescent throughout, trichomes (2–)4-rayed, 0.05–0.5(–0.6) mm. |
Basal leaves | rosulate; petiolate; petiole (0–1 cm), ciliate throughout; blade narrowly oblanceolate to linear, (0.4–)0.6–1.7(–2.5) cm × (1–)1.5–3.5(–5) mm, margins entire, (ciliate, trichomes usually simple, rarely 2-rayed, 0.2–1.1 mm), surfaces usually pubescent with short-stalked, pectinate trichomes, 0.15–0.5 mm, sometimes also with 4–6-rayed ones, (midvein usually obscure abaxially), sometimes glabrous adaxially. |
rosulate; shortly petiolate; petiole base ciliate (margin not ciliate, trichomes 2-rayed, 0.3–0.6 mm); blade oblanceolate to obovate, 0.4–1.2 cm × 2–5 mm, margins entire or, rarely, denticulate, surfaces pubescent with stalked, (2–)4-rayed trichomes, 0.15–0.4 mm. |
Cauline leaves | usually 0 (or 1, as a bract); sessile; blade linear to oblong, margins entire, surfaces pubescent as basal. |
0. |
Racemes | 3–14(–30)-flowered, usually ebracteate, rarely proximalmost flowers bracteate, elongated in fruit; rachis not flexuous, glabrous or pubescent as stem. |
10–20(–25)-flowered, ebracteate, considerably elongated in fruit; rachis not flexuous, pubescent as stems proximally. |
Flowers | sepals broadly ovate, 2.5–3.5(–4) mm, pubescent, (trichomes simple and 2- or 3-rayed); petals yellow (fading white), oblanceolate to obovate, 4–6 × 1.5–2.5 mm; anthers ovate, 0.3–0.5 mm. |
sepals broadly ovate, 2–2.5 mm, pubescent, (trichomes short-stalked, 3- or 4-rayed); petals yellow, obovate to oblanceolate, 3.7–6 × 1.5–2.5 mm; anthers ovate, 0.5–0.6 mm. |
Fruiting pedicels | ascending, straight, (2.5–)4–11(–27) mm, glabrous or pubescent, trichomes 2–5-rayed or pectinate. |
divaricate-ascending, straight (not expanded basally), 4–9 mm, pubescent, trichomes (2–)4-rayed, (0.05–0.25 mm). |
Fruits | broadly ovate to lanceolate, plane, flattened, 5–9(–11) × 2–4 mm; valves glabrous or puberulent, trichomes simple and 2-rayed, 0.05–0.3 mm; ovules 8–16(–20) per ovary; style 0.2–0.9 mm. |
lanceolate to broadly ovate, plane, flattened, 6–9 × 2–4.5 mm; valves pubescent, trichomes short-stalked, (2–)4-rayed, 0.05–0.25 mm; ovules 10–18 per ovary; style 0.4 0.8(–1) mm. |
Seeds | oblong, 1.1–1.5 × 0.7–1 mm. |
oblong, 1.2–1.5 × 0.7–0.8 mm. |
2n | = 112. |
= 26. |
Draba incerta |
Draba cusickii |
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Phenology | Flowering Jun–Aug. | Flowering Jun–Jul. |
Habitat | Rock outcrops, talus, gravelly areas, tundra | Basaltic outcrops, talus, rocky soil |
Elevation | 0-3300 m (0-10800 ft) | 2000-2700 m (6600-8900 ft) |
Distribution |
AK; CO; ID; MT; NV; UT; WA; WY; AB; BC; QC; YT
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OR
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Discussion | Draba incerta was shown by G. A. Mulligan (1972) to be sexually reproducing and 14-ploid with x = 8. It is often confused with the apomict D. oligosperma (2n = 32, 64). Draba incerta is readily separated from D. oligosperma by having well-formed (versus abortive) anthers and pollen, stalked (versus sessile) leaf trichomes, and ciliate (versus non-ciliate) basal leaves with obscure (versus prominent) midveins. Although both species have leafless scapes, one often finds a bract adnate to, or subtending, the proximalmost pedicel in D. incerta. Draba incerta is found near sea level in Alaska. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Draba cusickii was divided by R. C. Rollins (1993) into two varieties with significantly different morphologies and chromosome numbers. The Nevada endemic var. pedicellata (2n = 20) is here treated as a distinct species following M. D. Windham (2004). Draba cusickii has the same chromosome number as D. sobolifera but is readily distinguished from that species by having 4-rayed (versus simple or 2-rayed) fruit trichomes. Draba cusickii is known from Steens Mountain (Harney County). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 313. | FNA vol. 7, p. 304. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. exalata, D. incerta var. laevicapsula, D. incerta var. peasei, D. laevicapsula, D. peasei | D. sphaeroides var. cusickii |
Name authority | Payson: Amer. J. Bot. 4: 261. (1917) | B. L. Robinson ex O. E. Schulz: in H. G. A. Engler, Pflanzenr. 89[IV,105]: 105. (1927) |
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