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FNA | Family List | FNA Vol. 7 | Brassicaceae

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] 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.


1 Fruits sparsely to densely pubescent at least when young   (2)
+ Fruits glabrous   (4)
       
2 (1) Perennials; fruiting pedicels 1.5-3 mm; fruits subappressed to rachises; styles sparsely pubescent; ovules 10-18 per ovary; Wyoming.   14 Descurainia torulosa
+ Biennials; fruiting pedicels 6-31 mm; fruits not appressed to rachises; styles glabrous; ovules 16-64 per ovary; Arizona, California, Nevada, New Mexico   (3)
       
3 (2) Seeds biseriate; ovules 48-64 per ovary; fruits 1-1.3 mm wide; fruiting pedicels 13-31 mm.   1 Descurainia adenophora
+ Seeds uniseriate; ovules 16-40 per ovary; fruits 0.7-1 mm wide; fruiting pedicels 6-15 mm.   9 Descurainia obtusa
       
4 (1) Fruits usually fusiform, obovate, clavate, or broadly ellipsoid, rarely broadly linear (wider distally)   (5)
+ Fruits linear (sometimes oblong in D. brevisiliqua)   (7)
       
5 (4) Fruits usually clavate, rarely broadly linear (wider distally); seeds biseriate; ovules 16-40 per ovary; valves each with distinct midvein.   11 Descurainia pinnata
+ 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   (6)
       
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.   3 Descurainia californica
+ Fruits acute basally, obtuse apically; styles 0.05-0.3 mm; stems (1-)1.5-3.2(-4.1) dm, branched basally and distally.   10 Descurainia paradisa
       
7 (4) Perennials (short-lived); stems 0.1-0.15 dm; racemes not elongated in fruit; ovules 4-8 per ovary.   6 Descurainia kenheilii
+ 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)   (8)
       
8 (7) Fruits often strictly appressed to rachises; fruiting pedicels erect to erect-ascending.   4 Descurainia incana
+ Fruits not appressed to rachises; fruiting pedicels horizontal, divaricate, or ascending   (9)
       
9 (8) Leaf blades 2- or 3-pinnate; fruit septums appearing 2- or 3-veined.   12 Descurainia sophia
+ Leaf blades usually 1-pinnate (rarely 2-pinnate in D. sophioides); fruit septums not veined   (10)
       
10 (9) Plants eglandular; fruits 3-8(-10) mm; petals 0.7-1.2 mm; seeds 0.5-0.8 mm   (11)
+ Plants glandular or eglandular; fruits 8-30(-34) mm; petals 1.7-2.8 mm; seeds 0.9-1.5 mm   (12)
       
11 (10) Biennials; stems 6-11 dm, unbranched; ovules 10-28 per ovary; seeds biseriate.   2 Descurainia brevisiliqua
+ 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.   8 Descurainia nelsonii
       
12 (10) Flowers overtopped by developing fruits; ovules 30-62 per ovary.   13 Descurainia sophioides
+ Flowers not overtopped by developing fruits; ovules 14-32 per ovary   (13)
       
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.   5 Descurainia incisa
+ Plants not canescent; cauline leaf blades: distal segments linear or oblong, margins entire; fruits straight or slightly curved inward.   7 Descurainia longepedicellata

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