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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]

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 4

1 Fruit trichomes 2-7-rayed (at least on replum); petals white   (2)
+ Fruit trichomes simple and 2-5-rayed; petals white or yellow   (8)
2 (1) Racemes bracteate (at least basally)   (3)
+ Racemes ebracteate   (4)
3 (2) Racemes (10-)15-47(-63)-flowered, often considerably elongated in fruit; ovules 28-48 per ovary.   22 Draba cana
+ Racemes 2-5(-8)-flowered, slightly elongated in fruit; ovules 16-24 per ovary.   50 Draba inexpectata
4 (2) Petals 2-3.5 × 0.7-1.4 mm; fruits 1.5-2.5 mm wide   (5)
+ Petals 3.5-6 × 1.5-2.5 mm; fruits 2-3.5 mm wide   (6)
5 (4) Cauline leaves 1-3(-6); fruits usually twisted, rarely plane; rachises not flexuous in fruit; ovules 28-40 per ovary; California.   19 Draba breweri (in part)
+ Cauline leaf 1; fruits plane; rachises often slightly flexuous in fruit; ovules 12-24(-28) per ovary; Alaska, Canada, Greenland.   68 Draba nivalis (in part)
6 (4) Basal leaf blade margins dentate or denticulate; fruits usually slightly twisted, rarely plane; styles (0.2-)0.4-1 mm.   6 Draba arabisans (in part)
+ Basal leaf blade margins usually entire, rarely 1-toothed on each side; fruits plane; styles 0.1-0.6 mm   (7)
7 (6) Basal leaf blades with simple trichomes apically, abaxial surfaces with distinct midveins; seeds 0.8-1.1 × (0.6-)0.7-0.8 mm.   7 Draba arctica (in part)
+ Basal leaf blades without simple trichomes apically, abaxial surfaces with obscure midveins; seeds 0.6-0.8 × 0.4-0.6 mm.   25 Draba cinerea (in part)
8 (1) Petals yellow   (9)
+ Petals white   (11)
9 (8) Ovules 28-38(-44) per ovary; racemes basally bracteate, (10-)18-52(-72)-flowered; cauline leaves 5-20(-26); fruits (6-)9-14(-17) mm, often subappressed to rachis; stem trichomes non-crisped.   13 Draba aurea (in part)
+ Ovules 6-16(-18) per ovary; racemes ebracteate, 3-15(-18)-flowered; cauline leaves 1-4 (or 5); fruits 3-10 mm, not appressed to rachis; stem trichomes often crisped   (10)
10 (9) Plants matted, caudex branches creeping; stem trichomes dendritic; ovules 6-12 per ovary; se Utah.   90 Draba ramulosa
+ Plants not matted, caudex branches not creeping; stem trichomes stellate; ovules 10-16(-18) per ovary; Colorado.   110 Draba streptobrachia (in part)
11 (8) Styles (0.7-)1-2(-2.3) mm; fruits twisted; sw Colorado.   102 Draba smithii
+ Styles 0.05-0.6(-0.8) mm; fruits plane or slightly twisted; not sw Colorado   (12)
12 (11) Leaf blade margins dentate or denticulate; cauline leaves 2-25   (13)
+ Leaf blade margins entire; cauline leaves 1(-4)   (14)
13 (12) Leaf blade surfaces pubescent, trichomes cruciform or (2-)4-6-rayed (rays usually simple, rarely branched); plants with rhizomatous caudex.   16 Draba borealis (in part)
+ Leaf blade surfaces pubescent, trichomes stellate-pectinate, 4-8(-12)- rayed; plants without rhizomatous caudex (sometimes cespitose).   38 Draba glabella (in part)
14 (12) Rachises not flexuous; sepals persistent; fruits plane.   21 Draba californica (in part)
+ Rachises often slightly flexuous; sepals caducous; fruits slightly twisted or plane.   57 Draba lonchocarpa (in part)

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