Draba incerta |
Draba bifurcata |
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whitlow-wort, Yellowstone Draba, Yellowstone Draba whitlow-wort, Yellowstone whitlow-grass, Yellowstone whitlow-wort |
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Habit | Perennials; (cespitose, often pulvinate); caudex branched (dense with persistent leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Biennials or, rarely, perennials; caudex simple or branched; not 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). |
branched or unbranched, 1–3.9 dm, pubescent throughout or proximally, trichomes simple, 0.3–1.4 mm, often with smaller, 2 (or 3)-rayed ones. |
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. |
(soon withered); rosulate; petiolate; petiole ciliate, (trichomes simple, 0.4–1.1 mm); blade oblanceolate to spatulate, 1–7 cm × 2–12(–26) mm, margins entire or dentate (pubescent as petiole), surfaces pubescent, abaxially with simple trichomes, 0.6–1.1 mm, and stalked, 2- (or 3-)rayed ones, often smaller, adaxially with subsetiform, simple trichomes, 0.5–1.2 mm (rarely with fewer, stalked, 2-rayed ones). |
Cauline leaves | usually 0 (or 1, as a bract); sessile; blade linear to oblong, margins entire, surfaces pubescent as basal. |
(2–)6–15; sessile; blade lanceolate to ovate or oblong, margins dentate, surfaces pubescent as basal. |
Racemes | 3–14(–30)-flowered, usually ebracteate, rarely proximalmost flowers bracteate, elongated in fruit; rachis not flexuous, glabrous or pubescent as stem. |
10–51-flowered, ebracteate, elongated in fruit; rachis glabrous or pubescent as stem, not flexuous. |
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 ovate, 2.5–3.2 mm, pubescent, (trichomes simple and short-stalked, 2-rayed); petals yellow, oblanceolate, 4.5–6.5 × 1.5–2 mm; anthers oblong, 0.8–1.1 mm. |
Fruiting pedicels | ascending, straight, (2.5–)4–11(–27) mm, glabrous or pubescent, trichomes 2–5-rayed or pectinate. |
horizontal to divaricate, straight, 4–15 mm, glabrous or pubescent, trichomes simple and 2-rayed. |
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. |
elliptic-lanceolate, twisted (1 turn or plane), flattened, 6–10 × 2–2.5 mm; valves glabrous or sparsely puberulent, trichomes simple, 0.05–0.15 mm; ovules 14–20 per ovary; style (1–)2–3 mm. |
Seeds | oblong, 1.1–1.5 × 0.7–1 mm. |
oblong, 1.1–1.4 × 0.7–0.9 mm. |
2n | = 112. |
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Draba incerta |
Draba bifurcata |
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Phenology | Flowering Jun–Aug. | Flowering Jun–Jul. |
Habitat | Rock outcrops, talus, gravelly areas, tundra | Rocky areas, damp shady ravines, aspen-spruce communities |
Elevation | 0-3300 m (0-10800 ft) | 1800-3600 m (5900-11800 ft) |
Distribution |
AK; CO; ID; MT; NV; UT; WA; WY; AB; BC; QC; YT
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AZ |
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 bifurcata is distinguished from other North American species by a combination of yellow flowers with styles (1–)2–3 mm and almost exclusively simple trichomes on the abaxial surface of cauline leaf blades. It is known only from Chiricahua, Santa Catalina, and White mountains in Apache, Cochise, and Pima counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 313. | FNA vol. 7, p. 295. |
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. helleriana var. bifurcata |
Name authority | Payson: Amer. J. Bot. 4: 261. (1917) | (C. L. Hitchcock) Al-Shehbaz & Windham: Harvard Pap. Bot. 12: 411. (2007) |
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