Draba glabella |
Draba cuneifolia |
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golden Draba, rock whitlow-grass, smooth Draba, smooth whitlow-grass, smooth whitlow-mustard |
wedge leaf Draba |
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Habit | Perennials; (sometimes cespitose); caudex simple or branched; not scapose. | Annuals; scapose or subscapose. | ||||||||
Stems | branched or unbranched, (0.4–)1–3.5(–4.7) dm, often pubescent throughout (sometimes sparsely so distally), sometimes glabrous, trichomes simple and 2-rayed, (non-crisped), 0.2–1 mm, or subsessile, stellate-pectinate, and 3–8-rayed, 0.1–0.3 mm. |
(simple to many from or near base), unbranched, (0.2–) 0.3–2.7(–3.7) dm, hirsute or pubescent throughout, trichomes 3–4-rayed, 0.05–0.4 mm, (sometimes mixed proximally with simple or spurred ones, 0.5–1.2 mm). |
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Basal leaves | rosulate; petiolate; petiole ciliate, (trichomes simple, 0.1–0.8 mm); blade oblanceolate to spatulate or linear-oblanceolate, (0.6–)1–3.5(–5) cm × 2–8(–10) mm, margins dentate or denticulate, (pubescent as petiole), surfaces pubescent with non-crisped, minutely stalked, 4–8(–12)-rayed, stellate-pectinate trichomes, 0.15–0.6 mm, (midvein obscure abaxially), adaxially sometimes also with simple trichomes, or glabrous. |
not rosulate; petiole (obscure), not ciliate; blade oblanceolate to spatulate or broadly obovate, (0.4–)1–3.5(–5) cm × (2–)6–20(–28) mm, margins dentate (in distal 1/2), surfaces pubescent, abaxially with stalked, 2–4-rayed trichomes, 0.1–0.7 mm, adaxially similar or also with fewer, simple trichomes, 0.4–0.7 mm. |
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Cauline leaves | 2–17(–25); sessile; blade ovate to oblong, margins dentate to subentire, surfaces often pubescent as basal, or predominantly with simple trichomes adaxially. |
0–6 (on proximal 1/3 of stem); blade similar to basal. |
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Racemes | (5–)8–26(–34)-flowered, ebracteate or proximalmost 1 or 2 flowers bracteate, elongated in fruit; rachis not flexuous, usually glabrous, rarely pubescent as stem. |
10–50(–70)-flowered (throughout or on distal 1/3 of scape), ebracteate, elongated in fruit; rachis not flexuous, densely pubescent, trichomes 2–4-rayed. |
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Flowers | sepals oblong, 2–3.5 mm, pubescent, (trichomes simple and short-stalked, 2–4-rayed); petals white, broadly obovate, 4–5.5 × 1.5–3 mm; anthers ovate, 0.3–0.5 mm. |
(late ones cleistogamous, apetalous); sepals (green or pink), oblong, 1.5–2.5 mm, glabrous or pubescent, (trichomes simple); petals white, spatulate, (2–)2.5–4.5(–5) × 1–2 mm, (emarginate or obtuse); anthers ovate to oblong, (0.1–)0.25–0.4 mm. |
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Fruiting pedicels | divaricate-ascending to suberect, straight, (1–)3–10(–16) mm, glabrous or pubescent as stem. |
horizontal to divaricate-ascending, straight, (1–)2–7(–10) mm, pubescent as rachis. |
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Fruits | oblong to ovate or ovoid to lanceolate or linear-lanceolate, usually plane, rarely slightly twisted, flattened or inflated, (3–)5–12(–16) × 2–3.5 mm; valves glabrous or pubescent, trichomes simple or 2–4-rayed, 0.05–0.2(–0.4) mm; ovules (20–)24–36 per ovary; style 0.05–0.2(–0.5) mm. |
oblong to linear or lanceolate to broadly ovate, plane, flattened, (3–)6–12(–16) × 1.7–2.7(–3) mm; valves usually puberulent, rarely glabrous, trichomes simple, antrorse, 0.1–0.3 mm, (rarely with 2-rayed ones, or all trichomes short-stalked, 4-rayed, cruciform); ovules (12–)24–66(–72) per ovary; style 0.01–0.3(–0.4) mm. |
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Seeds | oblong, 0.9–1.1 × 0.5–0.7 mm. |
broadly ovoid, 0.5–0.7 × 0.4–0.5 mm. |
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2n | = 64, 80. |
= 30, 32. |
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Draba glabella |
Draba cuneifolia |
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Phenology | Flowering May–Aug. | |||||||||
Habitat | Rock outcrops, talus, rocky ridges and knolls, meadows, tundra, gravelly beaches sandy river margins, disturbed soils | |||||||||
Elevation | 0-1400 m (0-4600 ft) | |||||||||
Distribution |
AK; ME; VT; WI; BC; MB; NB; NL; NS; NT; NU; ON; QC; YT; Greenland; n Europe (n Russia); e Asia (Russian Far East, Siberia) |
AL; AR; AZ; CA; CO; FL; IL; KS; KY; LA; MO; MS; NC; NE; NM; NV; OH; OK; PA; SD; TN; TX; UT; n Mexico |
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Discussion | Draba glabella was reported by J. V. Freudenstein and J. K. Marr (1986) from Michigan, but that record likely was based on plants of D. arabisans, a highly variable species that occurs in that state. Draba glabella is extremely variable in indumentum, number of cauline leaves, fruiting pedicel length, fruit shape and size, style length, and seed number. M. L. Fernald (1934) divided it into five species and three varieties; R. C. Rollins (1993) recognized three species. Of these, G. A. Mulligan (1970, 1976) reduced D. laurentiana to synonymy of D. glabella and treated D. pycnosperma as a variety. Of all the segregates of D. glabella, var. pycnosperma might merit recognition. It is restricted to northwestern Newfoundland and northeastern Quebec, where var. glabella also grows. The main difference between the two varieties is the presence in var. pycnosperma of plump (versus flattened), ovoid to oblong fruits. Draba sornborgeri, recognized by Rollins as a distinct species, is merely a glabrescent form of D. glabella. Because of the tremendous morphological variability, wide distribution, extensive synonymy, and different chromosome numbers, D. glabella will require extensive molecular, cytological, and morphological studies to properly delimit the species and any potential infraspecific taxa. Some forms of Draba glabella approach both D. borealis and D. praealta, but these can be distinguished by examining the trichomes on the abaxial surfaces of basal leaf blades. In D. glabella, these trichomes are minutely stalked or subsessile and have branched rays. In the other two species, the trichomes have long stalks and the rays are always unbranched. The Linnaean name Draba hirta was applied to this species previously, and still is in Russia. The name is not typified, and the material at LINN is in bad condition and probably belongs to two species, D. glabella and D. norvegica, as recognized here. A typification of D. hirta may necessitate its re-introduction for this species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Varieties 3 (3 in the flora). Draba cuneifolia is highly variable in fruit shape and size, style length, ovule number per ovary, type of fruit indumentum, and length of the fruiting raceme in relation to the rest of the scape. Reported chromosome numbers also vary, but it is currently unclear whether this is the result of biologically relevant processes or erroneous counts. R. L. Hartman et al. (1975) divided the species into three varieties, a position followed by subsequent authors (e.g., R. C. Rollins 1993). Typical var. sonorae is rather distinct (see key below) and may deserve recognition as a separate species, as by O. E. Schulz (1927). Critical, population-based, molecular studies are needed to assess this. In the absence of such studies, we tentatively follow Hartman et al., recognizing three varieties that are distinguished primarily by the types of trichomes found on the fruits. Glabrous-fruited forms occasionally encountered in all three varieties can be difficult to identify. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 7, p. 307. | FNA vol. 7, p. 303. | ||||||||
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | D. arabisans var. canadensis, D. arabisans var. orthocarpa, D. canadensis, D. canadensis var. pycnosperma, D. daurica, D. glabella var. megasperma, D. glabella var. orthocarpa, D. glabella var. pycnosperma, D. henneana, D. hirta var. laurentiana, D. hirta var. pycnosperma, D. laurentiana, D. megasperma, D. norvegica var. pleiophylla, D. pycnosperma, D. sornborgeri | |||||||||
Name authority | Pursh: Fl. Amer. Sept. 2: 434. (1813) | Nuttall ex Torrey & A. Gray: Fl. N. Amer. 1: 108. (1838) | ||||||||
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