Draba glabella |
Draba howellii |
|
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golden Draba, rock whitlow-grass, smooth Draba, smooth whitlow-grass, smooth whitlow-mustard |
Howell's Draba, Howell's whitlow-grass, rosette Draba |
|
Habit | Perennials; (sometimes cespitose); caudex simple or branched; not scapose. | Perennials; (loosely cespitose); caudex branched (somewhat surculose, with persistent leaf remains, branches sometimes terminating in sterile rosettes); often 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. |
unbranched, (0.2–)0.4–1.1(–1.5) dm, usually pubescent throughout, rarely glabrous, trichomes simple and 2–4-rayed, 0.1–0.6 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; blade (somewhat fleshy), oblanceolate or spatulate to obovate, 0.4–1.6(–2.5) cm × (1.5–)3–6(–10) mm, margins entire, surfaces pubescent with stalked, cruciform, and fewer 2- or 3-rayed trichomes, 0.07–0.5 mm, rarely both surfaces glabrous and trichomes on margins, (midvein obscure abaxially). |
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. |
0–3 (or 4); sessile; blade ovate to oblong, margins entire, 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–)7–18(–25)-flowered, usually ebracteate, sometimes proximalmost 1 or 2 flowers bracteate, elongated in fruit; rachis not flexuous, usually pubescent as stem, rarely glabrous. |
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. |
sepals ovate, 2.5–3.2 mm, glabrous or pubescent, (trichomes 2–4-rayed); petals yellow, oblanceolate, 5.5–8 × 1–2 mm; anthers oblong, 0.7–0.9 mm. |
Fruiting pedicels | divaricate-ascending to suberect, straight, (1–)3–10(–16) mm, glabrous or pubescent as stem. |
divaricate-ascending, straight, (4–)7–10 mm, usually pubescent as stem, rarely glabrous. |
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. |
lanceolate to elliptic-lanceolate or broadly ovate, plane (not curved), strongly flattened, 6–11(–15) × 3–5 mm; valves usually pubescent, rarely glabrous, trichomes simple and 2–4-rayed, 0.05–0.3 mm; ovules 8–22 per ovary; style (0.7–)1.6–3 mm. |
Seeds | oblong, 0.9–1.1 × 0.5–0.7 mm. |
oblong, 1–1.6 × 0.8–1 mm, (sometimes distally appendaged). |
2n | = 64, 80. |
|
Draba glabella |
Draba howellii |
|
Phenology | Flowering May–Aug. | Flowering Jul–Aug. |
Habitat | Rock outcrops, talus, rocky ridges and knolls, meadows, tundra, gravelly beaches sandy river margins, disturbed soils | Rocky summits, cracks in granite walls, rock crevices |
Elevation | 0-1400 m (0-4600 ft) | 1900-2700 m (6200-8900 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; OR |
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.) |
Draba howellii is known from Siskiyou and Trinity counties, California, and Josephine County, Oregon. One collection, Tracy 14623 (DS, GH, UC), is unusual in having glabrous stems, pedicels, and leaf blade surfaces. In this regard, it resembles D. carnosula, but in all other respects (bracts, seeds, inflorescences, etc.), it is indistinguishable from D. howellii. For characteristics distinguishing the two species, see 23. D. carnosula. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 307. | FNA vol. 7, p. 312. |
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 | |
Name authority | Pursh: Fl. Amer. Sept. 2: 434. (1813) | S. Watson: Proc. Amer. Acad. Arts 20: 354. (1885) |
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