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52. Descurainia Webb & Berthelot, Hist. Nat. Îsles Canaries. 3(2,3): 72. 1836.
[name conserved]
Tansy mustard [For François Descurain, 1658-1740, French botanist and apothecary]
Barbara E. Goodson, Ihsan A. Al-Shehbaz
Huguenenia Reichenbach, name rejected; Sophia Adanson, name rejected
Annuals, biennials, or perennials [shrubs, subshrubs]; not scapose; glabrous, glabrate, or sparsely to densely pubescent, trichomes usually short-stalked, dendritic, rarely also simple, sometimes mixed with unicellular, glandular, clavate papillae. Stems erect or prostrate, unbranched or branched basally and/or distally. Leaves basal and cauline; petiolate or sessile; basal (often withered by flowering), rosulate, petiolate, blade (1-3-pinnate), margins entire or toothed; cauline petiolate or sessile, blade often similar to basal. Racemes (proximally sometimes bracteate), elongated or not in fruit. Fruiting pedicels divaricate or erect, slender. Flowers: sepals erect to spreading, ovate to oblong or linear; petals usually obovate or oblanceolate, rarely oblong, (shorter to longer than sepals), claw obsolete or distinct, (apex obtuse); stamens tetradynamous; filaments not dilated basally; anthers oblong to ovate, (apex obtuse); nectar glands confluent, subtending bases of stamens, median glands present. Fruits siliques or silicles, sessile, usually linear, oblong, clavate, or fusiform, rarely ellipsoid or obovoid, smooth or torulose, terete; valves each often with distinct midvein, usually glabrous, rarely pubescent; replum rounded; septum complete or perforated (membranous, not veined or with 1-3 longitudinal veins); ovules 5-100 per ovary; style usually absent, rarely distinct; stigma capitate. Seeds uniseriate or biseriate, plump, wingless, oblong or ellipsoid; seed coat (minutely reticulate), usually mucilaginous when wetted; cotyledons incumbent. x = 7.
Species 45-47 (14 in the flora): North America, Mexico, South America, Eurasia, n Africa, Atlantic Islands (Canary Islands).
SELECTED REFERENCES Bramwell, D. 1977. A revision of Descurainia Webb & Berth. section Sisymbriodendron (Christ) O. E. Schulz in the Canary Islands. Bot. Macar. 4: 31-53. Detling, L. E. 1939. A revision of the North American species of Descurainia. Amer. Midl. Naturalist 22: 481-520. Goodson, B. E. 2007. Molecular Systematics and Biogeography of Descurainia Webb & Berthel. (Brassicaceae). Ph.D. dissertation. University of Texas.
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| 1 |
Fruits sparsely to densely pubescent at least when young |
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(2) |
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Fruits glabrous |
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(4) |
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| 2 (1) |
Perennials; fruiting pedicels 1.5-3 mm; fruits subappressed to rachises; styles sparsely pubescent; ovules 10-18 per ovary; Wyoming. |
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14 Descurainia torulosa |
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Biennials; fruiting pedicels 6-31 mm; fruits not appressed to rachises; styles glabrous; ovules 16-64 per ovary; Arizona, California, Nevada, New Mexico |
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(3) |
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| 3 (2) |
Seeds biseriate; ovules 48-64 per ovary; fruits 1-1.3 mm wide; fruiting pedicels 13-31 mm. |
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1 Descurainia adenophora |
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Seeds uniseriate; ovules 16-40 per ovary; fruits 0.7-1 mm wide; fruiting pedicels 6-15 mm. |
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9 Descurainia obtusa |
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| 4 (1) |
Fruits usually fusiform, obovate, clavate, or broadly ellipsoid, rarely broadly linear (wider distally) |
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(5) |
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Fruits linear (sometimes oblong in D. brevisiliqua) |
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(7) |
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| 5 (4) |
Fruits usually clavate, rarely broadly linear (wider distally); seeds biseriate; ovules 16-40 per ovary; valves each with distinct midvein. |
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11 Descurainia pinnata |
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Fruits fusiform, obovate, or broadly ellipsoid (sometimes clavate in D. paradisa); seeds uniseriate (sometimes biseriate in D. paradisa); ovules 4-12 per ovary; valves each with obscure midvein |
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(6) |
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| 6 (5) |
Fruits long-acute basally and apically; styles (0.2-)0.3-0.6(-0.8) mm; stems (1.3-) 2-10.5(-13.5) dm, unbranched basally, branched distally. |
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3 Descurainia californica |
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Fruits acute basally, obtuse apically; styles 0.05-0.3 mm; stems (1-)1.5-3.2(-4.1) dm, branched basally and distally. |
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10 Descurainia paradisa |
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| 7 (4) |
Perennials (short-lived); stems 0.1-0.15 dm; racemes not elongated in fruit; ovules 4-8 per ovary. |
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6 Descurainia kenheilii |
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Annuals or biennials; stems (0.5-)0.9-12(-18) dm; racemes elongated considerably in fruit (sometimes slightly elongated in D. sophioides); ovules 10-62 per ovary (6-12 in D. nelsonii) |
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(8) |
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| 8 (7) |
Fruits often strictly appressed to rachises; fruiting pedicels erect to erect-ascending. |
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4 Descurainia incana |
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Fruits not appressed to rachises; fruiting pedicels horizontal, divaricate, or ascending |
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(9) |
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| 9 (8) |
Leaf blades 2- or 3-pinnate; fruit septums appearing 2- or 3-veined. |
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12 Descurainia sophia |
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Leaf blades usually 1-pinnate (rarely 2-pinnate in D. sophioides); fruit septums not veined |
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(10) |
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| 10 (9) |
Plants eglandular; fruits 3-8(-10) mm; petals 0.7-1.2 mm; seeds 0.5-0.8 mm |
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(11) |
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Plants glandular or eglandular; fruits 8-30(-34) mm; petals 1.7-2.8 mm; seeds 0.9-1.5 mm |
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(12) |
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| 11 (10) |
Biennials; stems 6-11 dm, unbranched; ovules 10-28 per ovary; seeds biseriate. |
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2 Descurainia brevisiliqua |
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Annuals; stems (0.7-)0.9-3.2(-4.5) dm, usually branched at or near base, rarely unbranched; ovules 6-12 per ovary; seeds uniseriate. |
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8 Descurainia nelsonii |
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| 12 (10) |
Flowers overtopped by developing fruits; ovules 30-62 per ovary. |
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13 Descurainia sophioides |
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Flowers not overtopped by developing fruits; ovules 14-32 per ovary |
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(13) |
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| 13 (12) |
Plants canescent or not; cauline leaf blades: distal segments oblong to lanceolate, or linear, margins dentate, denticulate or entire; fruits straight or strongly curved inward. |
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5 Descurainia incisa |
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Plants not canescent; cauline leaf blades: distal segments linear or oblong, margins entire; fruits straight or slightly curved inward. |
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7 Descurainia longepedicellata |
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List of lower taxa
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