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FNA | Family List | FNA Vol. 7 | Brassicaceae

9. Draba Linnaeus, Sp. Pl. 2: 642. 1753; Gen. Pl. ed. 5, 291. 1754.

[Greek drabe, acrid, for taste of mustard plant] [Greek drabe, acrid, for taste of mustard plant]

Ihsan A. Al-Shehbaz, Michael D. Windham, Reidar Elven

Abdra Greene; Erophila de Candolle; Nesodraba Greene; Tomostima Rafinesque

Annuals, biennials, or perennials [subshrubs]; (caudex simple or branched); scapose or not; glabrous or pubescent, trichomes stalked or sessile, simple, forked, cruciform, stellate, malpighiaceous, or dendritic, often more than 1 kind present. Stems usually erect to ascending, sometimes decumbent or prostrate, unbranched or branched (usually distally). Leaves usually basal and cauline, sometimes cauline absent; petiolate or sessile; basal usually rosulate, usually petiolate, rarely sessile, blade margins usually entire or toothed, rarely pinnately lobed; cauline (when present), petiolate or sessile, blade (base cuneate [auriculate]), margins entire or dentate. Racemes (often corymbose, sometimes bracteate), elongated or not in fruit. Fruiting pedicels (proximalmost) erect or ascending to divaricate, slender. Flowers: sepals (rarely persistent), erect, ascending, or, rarely, spreading, ovate or oblong [elliptic], lateral pair not saccate or subsaccate basally; petals (erect or ascending to patent), yellow, white, pink, purple, or orange [red], obovate, spatulate, oblanceolate, or linear [orbicular, oblong], (longer than or, rarely, shorter than sepals), claw obscurely to well-differentiated from blade, (apex obtuse, rounded, notched, or, rarely, deeply 2-lobed); stamens slightly to strongly tetradynamous; filaments dilated or not basally, (glabrous); anthers ovate or oblong, (not apiculate); nectar glands (1, 2, or 4), distinct or confluent, subtending bases of stamens, median glands present or absent. Fruits silicles or siliques, sessile, ovate, lanceolate, elliptic, oblong, linear, suborbicular, ovoid, or subglobose, plane or spirally twisted, smooth, (not keeled, unappendaged), usually latiseptate, rarely terete; valves (papery), each with distinct or obscure midvein and lateral veins, glabrous or pubescent; replum rounded; septum complete; ovules 4-70(-88) per ovary; style obsolete or distinct; stigma capitate. Seeds biseriate, oblong, ovate, or orbicular, usually flattened (slightly flattened in D. aleutica, D. verna), usually not winged (winged in D. asterophora, D. brachycarpa, D. carnosula, D. pterosperma); seed coat (minutely reticulate), not mucilaginous when wetted; cotyledons accumbent. x = 6-12.

Species ca. 380 (121 in the flora): North America, Mexico, South America (Andes, Colombia to Patagonia), Europe, Asia, nw Africa; alpine and boreal, rarely in temperate and low-elevation areas of North America and Eurasia.

SELECTED REFERENCES Beilstein, M. A. and M. D. Windham. 2003. A phylogenetic analysis of western North American Draba (Brassicaceae) based on nuclear ribosomal DNA sequences from the ITS region. Syst. Bot. 28: 584-592. Ekman, E. 1929. Studies in the genus Draba. Svensk Bot. Tidskr. 23: 476-495. Ekman, E. 1930. Contribution to the Draba flora of Greenland. II. Svensk Bot. Tidskr. 24: 280-297. Ekman, E. 1931. Contribution to the Draba flora of Greenland. III. Some notes on the arctic, especially the Greenland drabas of the sections Aizopsis and Chrysodraba DC. Svensk Bot. Tidskr. 25: 465-494. Ekman, E. 1932. Contribution to the Draba flora of Greenland. IV. Svensk Bot. Tidskr. 26: 431-447. Fernald, M. L. 1934. Draba in temperate northeastern America. Rhodora 36: 241-261, 285-305, 314-344, 353-371, 392-404. Hitchcock, C. L. 1941. A Revision of the Drabas of Western North America. Seattle. [Univ. Wash. Publ. Biol. 11.] Koch, M. and I. A. Al-Shehbaz. 2002. Molecular data indicate complex intra- and intercontinental differentiation of American Draba (Brassicaceae). Ann. Missouri Bot. Gard. 89: 88-109. Mulligan, G. A. 1976. The genus Draba in Canada and Alaska: Key and summary. Canad. J. Bot. 54: 1386-1393. Payson, E. B. 1917. The perennial scapose drabas of North America. Amer. J. Bot. 4: 253-267. Schulz, O. E. 1927. Cruciferae—Draba, Erophila. In: H. G. A. Engler, ed. 1900-1953. Das Pflanzenreich…. 107 vols. Berlin. Vol. 89[IV,105], pp. 1-396.


Group 8

1 Abaxial surface of leaf blades with pectinate, subpectinate, subdendritic, or stellate with 7-16-rayed trichomes   (2)
+ Abaxial surface of leaf blades with simple, cruciform, or 2-4(-6)-rayed trichomes   (12)
       
2 (1) Leaves, pedicels, and sepals with sessile or subsessile, pectinate trichomes   (3)
+ Leaves, pedicels, and sepals with stalked, stellate to subdendritic trichomes   (5)
       
3 (2) Fruit valves pubescent, trichomes pectinate; ovules 4-8 per ovary.   80 Draba pectinipila
+ Fruit valves glabrous or pubescent, trichomes simple or 2-rayed; ovules (6-)8-16 (-20) per ovary   (4)
       
4 (3) Fruits 5-9(-11) mm, flattened; petals 4-6 mm; sepals 2.5-3.5(-4) mm; leaf midvein usually obscure.   48 Draba incerta (in part)
+ Fruits 3-6(-7) mm, inflated; petals 2.5-4 mm; sepals 1.5-3 mm; leaf midvein prominent.   73 Draba oligosperma (in part)
       
5 (2) Petals white or creamy white   (6)
+ Petals yellow   (9)
       
6 (5) Sepals caducous; fruit valves glabrous; Alaska, Northwest Territories, Yukon   (7)
+ Sepals persistent; fruit valves usually pubescent, rarely glabrous (D. californica); e California, w Nevada   (8)
       
7 (6) Stems pubescent throughout, trichomes 8-15-rayed; petals spatulate to oblanceolate, 2-3.5 × 0.8-1.4 mm; rachises and fruiting pedicels pubescent; styles 0.1-0.4 mm.   68 Draba nivalis (in part)
+ Stems pubescent proximally, trichomes 2-9-rayed; petals obovate, 4.4-5.5 × 2-3 mm; rachises and fruiting pedicels usually glabrous, rarely sparsely pubescent; styles 0.3-0.8 mm.   76 Draba palanderiana
       
8 (6) Fruits usually twisted, rarely plane, with 2-5-rayed trichomes; fruiting pedicels 1.5-3(-4) mm.   19 Draba breweri (in part)
+ Fruits plane, with simple and 2- or 3-rayed trichomes, rarely glabrous; fruiting pedicels (2-)4-9(-12) mm.   21 Draba californica (in part)
       
9 (5) Fruits 4-11 mm, flattened, twisted or plane   (10)
+ Fruits 2-5(-6) mm, inflated (at least basally), plane   (11)
       
10 (9) Styles (0.7-)1-1.8(-2.4) mm; fruits symmetric; fruiting pedicels (4-) 5-12(-19) mm; c Idaho.   9 Draba argyrea (in part)
+ Styles (0.1-)0.3-0.7(-1) mm; fruits often asymmetric; fruiting pedicels 2-5(-7) mm; ec California.   100 Draba sierrae (in part)
       
11 (9) Racemes (4-)6-18(-23)-flowered, elongated in fruit; petals 4-6 mm; fruiting pedicels 4-9(-13) mm; c Idaho.   105 Draba sphaerocarpa
+ Racemes 2-5(-10)-flowered (subumbellate), not or slightly elongated in fruit; petals 2.8-4 mm; fruiting pedicels 1.5-3(-6) mm; e California, w Nevada.   114 Draba subumbellata
       
12 (1) Plants stoloniferous; basal leaves not rosulate.   72 Draba ogilviensis (in part)
+ Plants not stoloniferous (usually cespitose); basal leaves usually rosulate   (13)
       
13 (12) Petals white   (14)
+ Petals yellow   (16)
       
14 (13) Sepals persistent; fruits slightly inflated basally; petals 1.5-2 × 0.5-0.6 mm.   64 Draba monoensis (in part)
+ Sepals caducous; fruits flattened; petals 2-6 × 0.8-2.8 mm   (15)
       
15 (14) Styles 0.1-0.7 mm; fruit valves usually glabrous, rarely pubescent, trichomes simple (along margin); Alaska, Alberta, British Columbia, Northwest Territories, Yukon.   52 Draba juvenilis (in part)
+ Styles (0.7-)1-1.8(-2.1) mm; fruit valves with simple and 2-rayed trichomes; e Nevada.   82 Draba pennellii (in part)
       
16 (13) Abaxial surface of leaf blades with cruciform trichomes; ovules 16-30 per ovary.   52 Draba juvenilis (in part)
+ Abaxial surface of leaf blades with 2-6-rayed trichomes; ovules 4-18(-22) per ovary   (17)
       
17 (16) Racemes (15-)30-75-flowered; Arizona.   11 Draba asprella
+ Racemes 3-20(-27)-flowered; not Arizona   (18)
       
18 (17) Styles (0.7-)1.6-3 mm; petals 5.5-8 mm; anthers 0.7-0.9 mm.   46 Draba howellii (in part)
+ Styles 0.3-1.4 mm; petals 3.5-5.5(-6) mm; anthers 0.4-0.6 mm   (19)
       
19 (18) Fruit valves glabrous or pubescent, trichomes simple and 2-rayed; fruiting pedicels usually expanded basally   (20)
+ Fruit valves pubescent, trichomes 2-6-rayed; fruiting pedicels not expanded basally   (21)
       
20 (19) Petals 3.5-5.5 mm; fruiting pedicels horizontal to divaricate; ovules 8-16 per ovary.   81 Draba pedicellata (in part)
+ Petals 2.7-4 mm; fruiting pedicels divaricate-ascending; ovules 4-10 (-12) per ovary.   106 Draba sphaeroides (in part)
       
21 (19) Fruits flattened, 2-4.5 mm wide, 10-18-seeded; styles 0.4-0.8(-1) mm; racemes 10-20(-25)-flowered; surface of leaf blades pubescent with (2-) 4-rayed trichomes; se Oregon.   32 Draba cusickii
+ Fruits inflated basally, 3.5-5 mm wide, 8-12-seeded; styles (0.5-)0.7-1.4 mm; racemes 5-10(-16)-flowered; surface of leaf blades pubescent with 2-6-rayed trichomes; Alberta, British Columbia, Colorado, Utah, Wyoming, Yukon.   116 Draba ventosa

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