Draba exunguiculata |
Draba macounii |
|
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clawless Draba |
Macoun's Draba, Macoun's whitlow-grass |
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Habit | Perennials; (densely cespitose); caudex branched (covered with persistent, somewhat thickened, dry petioles); not scapose. | Perennials; (cespitose); caudex simple or branched (with persistent leaf bases, branches sometimes terminating in sterile rosettes); scapose. |
Stems | unbranched, 0.15–0.7 dm, glabrous throughout or sparsely pubescent, trichomes simple, 0.3–0.9 mm. |
unbranched, (0.06–)0.1–0.4(–0.6) dm, usually pubescent, rarely glabrous, trichomes simple and stalked, 2–4-rayed, 0.15–0.9 mm. |
Basal leaves | rosulate; petiolate; petiole ciliate, (trichomes simple, 0.3–1.1 mm); blade linear to linear-oblanceolate, (0.5–)0.8–2(–2.5) cm × 1–3 mm, margins entire, (pubescent as petiole), surfaces abaxially sparsely pubescent with simple and stalked, 2- or 3-rayed trichomes, 0.1–0.4 mm, adaxially glabrous or subapically sparsely pubescent with simple trichomes. |
rosulate; petiole (obscure), margin ciliate, (trichomes simple, 0.3–1 mm); blade oblanceolate to obovate, (0.4–)0.6–1(–1.5) cm × (1–)2–4 mm, margins entire, surfaces usually pubescent abaxially, rarely glabrous, with short-stalked, 2–5-rayed trichomes, 0.1–0.5 mm, adaxially glabrous or pubescent with simple and short-stalked, 2-rayed trichomes. |
Cauline leaves | 1–4; sessile; blade linear to linear-oblanceolate, margins entire, surfaces pubescent as basal. |
0. |
Racemes | 4–13(–20)-flowered, ebracteate, elongated in fruit; rachis not flexuous, usually glabrous, rarely sparsely pubescent, trichomes simple, to 1 mm. |
3–10(–13)-flowered, ebracteate, (subumbellate), slightly elongated in fruit; rachis not flexuous, usually pubescent as stem, rarely glabrous. |
Flowers | sepals ovate, 2–2.5 mm, pubescent, (trichomes simple); petals (erect), yellow, obovate, 2–2.5(–3) × 1.5–2 mm, (not clawed); anthers oblong, 0.6–0.9 mm. |
sepals ovate, 1.5–2.5 mm, glabrous or pubescent, (trichomes simple and short-stalked, 2- or 3-rayed); petals pale yellow, spatulate, 2.7–4 × 1–2 mm; anthers ovate, 0.2–0.3 mm. |
Fruiting pedicels | divaricate-ascending, straight or slightly curved upward, 1–6 mm, usually glabrous, rarely with few, simple trichomes. |
horizontal to divaricate (not expanded basally), curved upward, 1.5–4.5(–6) mm, abaxially pubescent as stem, adaxially usually glabrous, rarely throughout. |
Fruits | lanceolate to oblong-lanceolate, plane, flattened, 5–13 × 1.5–3 mm; valves glabrous; ovules 20–24 per ovary; style 0.3–1 mm. |
subglobose to ovoid or ellipsoid, plane, inflated at least basally, 4–8 × 2–4.5 mm; valves glabrous; ovules 10–14(–16) per ovary; style 0.1–0.5 mm. |
Seeds | ovoid, 1–1.3 × 0.6–0.8 mm. |
ovoid, 1–1.2 × 0.6–0.8 mm. |
2n | = 56 ± 5. |
= 64. |
Draba exunguiculata |
Draba macounii |
|
Phenology | Flowering Jul–Aug. | Flowering Jun–Aug. |
Habitat | Open knolls, talus, gravelly alpine slopes, rocky alpine tundra | Rock outcrops, talus, tundra |
Elevation | 3600-4300 m (11800-14100 ft) | 700-2800 m (2300-9200 ft) |
Distribution |
CO |
AK; MT; AB; BC; YT |
Discussion | Of conservation concern. Draba exunguiculata occupies alpine areas of Clear Creek, El Paso, Grand, and Summit counties in central Colorado. Draba grayana is found in the same general area; both species are apomicts that occasionally grow sympatrically. Draba exunguiculata is easily distinguished from D. grayana by having stems and fruiting pedicels glabrous or sparsely pubescent with simple trichomes (versus moderately to densely pubescent with simple and 2- or 3-rayed trichomes), and by having erect, non-clawed petals, 2–3 mm and slightly longer than sepals (versus flared, clawed petals 3–4.5 mm and nearly twice as long as sepals). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Draba macounii is often confused with the circumpolar decaploid (2n = 80) D. alpina. Plants of the former have scapes (0.6–)1–4(–6) cm, fruiting pedicels divaricate to horizontal, gently curved, and 1.5–4.5(–6) mm, and petals pale yellow, spatulate, and 2.7–4 × 1–2 mm. By contrast, D. alpina has scapes (3–)5–17(–28) cm, fruiting pedicels divaricate-ascending to ascending, often straight, and (3–)4–14(–30) mm, and petals bright yellow, obovate, and 3.5–5 × 1.7–2.5 mm. R. C. Rollins (1993) indicated that the species occurs in Colorado, but we have not seen any material from that state. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 306. | FNA vol. 7, p. 318. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | D. chrysantha var. exunguiculata, D. chrysantha | |
Name authority | (O. E. Schulz) C. L. Hitchcock: Revis. Drabas W. N. Amer., 46. (1941) | O. E. Schulz: in H. G. A. Engler, Pflanzenr. 89[IV,105]: 97. (1927) |
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