Draba glabella |
Draba praealta |
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golden Draba, rock whitlow-grass, smooth Draba, smooth whitlow-grass, smooth whitlow-mustard |
Draba, tall Draba, tall whitlow-grass, tall whitlow-grass Draba |
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Habit | Perennials; (sometimes cespitose); caudex simple or branched; not scapose. | Annuals or perennials; (short-lived); caudex simple or branched; not scapose. |
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. |
branched or unbranched, (0.5–)0.8–3.2(–3.8) dm, pubescent throughout, trichomes 3–5-rayed, 0.1–0.4 mm, with simple and 2-rayed ones, 0.4–1 mm. |
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. |
rosulate; subsessile; petiole base ciliate, (trichomes simple and 2-rayed, 0.2–0.8 mm); blade oblanceolate, (0.7–)1–3.5(–4.5) cm × 1.5–7(–9) mm, margins usually dentate, rarely entire, surfaces pubescent, abaxially with stalked, 3–6-rayed trichomes, 0.1–0.5 mm, adaxially with stalked, 3–5-rayed, 0.1–0.6 mm, and simple ones, to 0.8 mm. |
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. |
(1 or) 2–5(–9); sessile; blade ovate to lanceolate, margins dentate or entire, surfaces pubescent as basal. |
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. |
(5–)8–30(–37)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. |
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-season ones petaliferous); sepals ovate, 1.7–2.5 mm, pubescent, (trichomes simple and stalked, 2-rayed); petals white, oblanceolate to spatulate, 2.8–3.5(–4) × 0.8–1.2 mm; anthers ovate, 0.2–0.3 mm. |
Fruiting pedicels | divaricate-ascending to suberect, straight, (1–)3–10(–16) mm, glabrous or pubescent as stem. |
divaricate-ascending to ascending or suberect (not appressed to rachis), straight, (3–)4–10(–12) mm, pubescent, trichomes 3–5-rayed (0.1–0.4 mm), and sometimes simple. |
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. |
(erect, not appressed to rachis) lanceolate to linear-lanceolate, plane, flattened, (5–)7–12(–15) × 1.5–2.5(–3) mm; valves puberulent, trichomes simple and short-stalked, 2–4-rayed, 0.05–0.25 mm; ovules (24–)30–52 per ovary; style 0.03–0.1(0.15) mm. |
Seeds | oblong, 0.9–1.1 × 0.5–0.7 mm. |
oblong, 0.8–1.1 × 0.5–0.6 mm, (often apiculate). |
2n | = 64, 80. |
= 56. |
Draba glabella |
Draba praealta |
|
Phenology | Flowering May–Aug. | Flowering Jun–Aug. |
Habitat | Rock outcrops, talus, rocky ridges and knolls, meadows, tundra, gravelly beaches sandy river margins, disturbed soils | Rocky pine slopes, subalpine areas, alpine meadows, grassy volcanic ridges, woodlands, damp rocky areas, limestone talus, shale cliffs, steep hillsides |
Elevation | 0-1400 m (0-4600 ft) | 1200-2900 m (3900-9500 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) |
CA; ID; MT; NV; OR; WA; WY; AB; BC; NT; YT; e Asia (Russian Far East [Chukchi Peninsula])
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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.) |
Morphological and chromosomal evidence (M. D. Windham, unpubl.) suggests that Draba praealta may be an allopolyploid originating through hybridization between D. albertina and D. cana. Both R. C. Rollins (1993) and N. H. Holmgren (2005b) placed D. lonchocarpa var. dasycarpa in the synonymy of D. lonchocarpa. G. A. Mulligan (1974) indicated that the type of var. dasycarpa does not belong to that species and he correctly annotated its isotype (Macoun 64454, CAN) as D. praealta. Mulligan (1976) and Rollins indicated that D. praealta occurs in Alaska, but we have not seen unequivocal material from the state. We have not seen the material on which A. E. Katenin and V. V. Petrovsky (1995) based their record from the Russian Far East. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 307. | FNA vol. 7, p. 331. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling 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 | D. cascadensis, D. columbiana, D. dolichopoda, D. lapilutea, D. lonchocarpa var. dasycarpa, D. praealta var. yellowstonensis, D. yellowstonensis |
Name authority | Pursh: Fl. Amer. Sept. 2: 434. (1813) | Greene: Pittonia 3: 306. (1898) |
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