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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 7

1 Abaxial surface of leaf blades with some 7-16-rayed trichomes   (2)
+ Abaxial surface of leaf blades with simple and/or 2-5 (or 6)-rayed or malpighiaceous trichomes   (9)
       
2 (1) Trichomes pectinate; leaf blades with midvein prominent abaxially; fruits inflated (at least basally).   73 Draba oligosperma (in part)
+ Trichomes stellate or, rarely, subdendritic; leaf blades with midvein obscure abaxially (prominent in D. lactea); fruits flattened   (3)
       
3 (2) Leaf blades with midvein strongly thickened abaxially.   55 Draba lactea (in part)
+ Leaf blades with midvein obscure abaxially   (4)
       
4 (3) Petals white, 2-4 mm   (5)
+ Petals yellow (white fading yellowish in D. palanderiana), 4-6 mm   (7)
       
5 (4) Fruits linear to narrowly lanceolate or oblong, 6-15(-18) mm; ovules 16-24(-28) per ovary; rachises often slightly flexuous.   57 Draba lonchocarpa (in part)
+ Fruits ovate to oblong, 4-8 mm; ovules 12-16 per ovary; rachises not flexuous   (6)
       
6 (5) Fruits not appressed to rachises; petals 2-3 mm wide; fruiting pedicels (4-)5-9 mm; style 0.4-1 mm.   65 Draba mulliganii (in part)
+ Fruits appressed to rachises; petals 0.7-1.2 mm wide; fruiting pedicels 0.5-2(-4) mm; style 0.05-0.1 mm.   86 Draba porsildii (in part)
       
7 (4) Ovules 18-32 per ovary; seeds 0.9-1.1 × 0.5-0.7 mm; fruit valves glabrous.   76 Draba palanderiana (in part)
+ Ovules 8-16 per ovary; seeds 1.2-2 × 0.8-1.3 mm; fruit valves often puberulent, sometimes glabrous   (8)
       
8 (7) Styles (0.7-)1-1.8(-2.4) mm; petiole bases and leaf blade margins not ciliate; sepals pubescent, trichomes 4-6-rayed; Idaho.   9 Draba argyrea (in part)
+ Styles 0.5-0.9(-1.1) mm; petiole bases and leaf blade margins ciliate; sepals pubescent, trichomes simple and 2-rayed; Alaska, British Columbia, Washington, Yukon.   93 Draba ruaxes
       
9 (1) Leaf blades with malpighiaceous trichomes.   99 Draba sibirica (in part)
+ Leaf blades with simple, forked, stellate, or subdendritic trichomes   (10)
       
10 (9) Abaxial surface of leaf blades with mixture of simple and 2(-4)-rayed trichomes   (11)
+ Abaxial surface of leaf blades with 2-6-rayed trichomes   (18)
       
11 (10) Petals yellow (rarely fading white); fruits not inflated basally (flattened)   (12)
+ Petals white; fruits inflated basally (flattened in D. fladnizensis)   (15)
       
12 (11) Perennials with poorly developed caudex, not stoloniferous; petals 1.5-3.2 × 0.5-1.2 mm; styles 0.01-0.12 mm; ovules (20-)24-38(-44) per ovary   (13)
+ Perennials with branched caudex or stoloniferous; petals 3.5-6 × 2-3.5 mm; styles 0.4-1 mm; ovules 8-20 per ovary   (14)
       
13 (12) Abaxial surface of leaf blades pubescent with 2-4-rayed trichomes; stems pubescent, trichomes simple and 2-4-rayed.   2 Draba albertina (in part)
+ Abaxial surface of leaf blades glabrous or with some simple and 2-rayed trichomes; stems usually glabrous, rarely sparsely pubescent basally, trichomes simple.   29 Draba crassifolia (in part)
       
14 (12) Plants stoloniferous; basal leaves not rosulate, blades with obscure midvein; fruits oblong, 2-3 mm wide.   72 Draba ogilviensis (in part)
+ Plants not stoloniferous; basal leaves rosulate, blades with prominent, persistent midvein; fruits elliptic to lanceolate, 3-4 mm wide.   84 Draba pilosa (in part)
       
15 (11) Basal leaf blades with a prominent midvein   (16)
+ Basal leaf blades with obscure midvein   (17)
       
16 (15) Fruits flattened, elliptic-lanceolate to oblong, 1.5-2 mm wide; rachises glabrous; petals 2-3.5 mm.   37 Draba fladnizensis (in part)
+ Fruits slightly inflated, ovoid to oblong, 2-3 mm wide; rachises usually pubescent, rarely glabrous; petals 1.5-2(-2.5) mm.   113 Draba subcapitata (in part)
       
17 (15) Sepals persistent; fruiting pedicels 1-2.5(-4) mm; petals 1.5-2 mm; fruits (2-)3-5 × (1.2-)1.5-2.5 mm; e California.   64 Draba monoensis (in part)
+ Sepals caducous; fruiting pedicels (3-)5-10(-17) mm; petals 3-5 mm; fruits 4-8(-10) × 2.5-4 mm; s Utah.   112 Draba subalpina (in part)
       
18 (10) Caudex simple or branched, without sterile rosettes; styles 0.01-0.15(-0.2) mm   (19)
+ Caudex often branched, with sterile rosettes; styles (0.1-)0.2-3 mm   (21)
       
19 (18) Sepals pubescent with simple and 2- or 3-rayed trichomes; abaxial surface of leaf blades with (2-)4(-6)-rayed trichomes; s Nevada.   78 Draba paucifructa (in part)
+ Sepals glabrous or with simple trichomes; abaxial surface of leaf blades with 2-4-rayed trichomes; not s Nevada   (20)
       
20 (19) Stems proximally with simple and 2-rayed trichomes; adaxial surface of leaf blades with simple and 2-rayed trichomes; anthers 0.15-0.25 mm; fruits (4-)6-12(-15) mm.   2 Draba albertina (in part)
+ Stems proximally with 2-4-rayed trichomes; adaxial surface of leaf blades with 2-4-rayed trichomes; anthers 0.25-0.4 mm; fruits (8-) 10-17(-20) mm.   108 Draba stenoloba (in part)
       
21 (18) Abaxial surface of leaf blades with some pectinate or submalpighiaceous trichomes   (22)
+ Abaxial surface of leaf blades with cruciform or 2-5-rayed trichomes   (23)
       
22 (21) Abaxial surface of leaf blades with pectinate and some 4-6-rayed trichomes; ovules 8-16(-20) per ovary.   48 Draba incerta (in part)
+ Abaxial surface of leaf blades with submalpighiaceous trichomes; ovules 20-28 per ovary.   53 Draba kassii
       
23 (21) Fruits inflated (at least basally)   (24)
+ Fruits flattened   (26)
       
24 (23) Styles 0.1-0.5 mm; fruiting pedicels not expanded basally; anthers 0.2-0.3 mm; Alaska, Alberta, British Columbia, Montana, Yukon.   59 Draba macounii (in part)
+ Styles 0.3-1(-1.3) mm; fruiting pedicels usually expanded basally; anthers 0.4-0.5 mm; Nevada, Utah   (25)
       
25 (24) Plants densely pulvinate; petals 2.7-4 mm; fruiting pedicels divaricate- ascending.   106 Draba sphaeroides (in part)
+ Plants loosely cespitose; petals 3.5-5.5 mm; fruiting pedicels divaricate, horizontal, or slightly descending.   81 Draba pedicellata (in part)
       
26 (23) Seeds 1.8-2.8 × 1.2-2 mm, winged.   12 Draba asterophora (in part)
+ Seeds 0.7-2(-2.6) × 0.4-1(-1.4) mm, not winged   (27)
       
27 (26) Fruits twisted, curved.   98 Draba sharsmithii
+ Fruits plane, not curved (straight)   (28)
       
28 (27) Leaf blades with prominent midveins, margins ciliate (trichomes simple).   35 Draba densifolia (in part)
+ Leaf blades with obscure midveins, margins not ciliate   (29)
       
29 (28) Fruits 2.5-4.5(-5.5) mm wide; rachises often flexuous; fruiting pedicels expanded basally or not.   81 Draba pedicellata (in part)
+ Fruits 1.5-3 mm wide; rachises not flexuous; fruiting pedicels not expanded basally   (30)
       
30 (29) Ovules 4-10(-12) per ovary; seeds 0.8-1.3 mm wide   (31)
+ Ovules 12-30 per ovary; seeds 0.4-0.8 mm wide   (32)
       
31 (30) Styles (0.1-)0.3-0.8 mm; petals 4-5(-6) × 1.2-2 mm; sepals 1.5-2 mm; ec California.   30 Draba cruciata (in part)
+ Styles 0.6-1.7 mm; petals 5-7 × 2-3 mm; sepals 2.5-4 mm; n Utah.   60 Draba maguirei (in part)
       
32 (30) Abaxial surface of leaf blades pubescent, trichomes cruciform; racemes (2-)4-13(-18)-flowered; petals 3-5 mm; Alaska, Alberta, British Columbia, Northwest Territories, Yukon.   52 Draba juvenilis (in part)
+ Abaxial surface of leaf blades pubescent, trichomes (2-)4 (or 5)-rayed; racemes 14-36-flowered; petals 5-6 mm; sw Utah.   121 Draba zionensis

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