Descurainia Webb & Berthelot
Descurainia is a genus of ca. 45-47 species (Goodson & Al-Shehbaz 2010). Most species are native to the Americas, others to the Atlantic Islands, northern Africa and Eurasia. One species is native (or at least archaeophytic) in parts of Belgium, especially in coastal areas: Descurainia sophia (L.) Webb ex Prantl (Lambinon & al. 2004). It is much decreasing lately (Van Landuyt 2006) and now much more frequently occurs as an introduction. It is, for instance, a very characteristic grain alien in port areas.
There is much incongruence in North American Descurainia, probably as a result of hybridization processes. Molecular data highlight possible problems with current species circumscriptions, especially within North American taxa such as Descurainia incisa, D. obtusa and D. pinnata (Goodson & al. 2011).
- Fruit clavate, 4-13(-17) mm long, not torulose, septum not veined. Basal leaf blades 1-2 pinnate. Seeds biseriate (in two rows) ===Descurainia pinnata
- Fruit narrowly linear, (12-) 15-27(-40) mm long, torulose, septum appearing 2-3 veined. Basal leaf blades 2-3 pinnate. Seeds uniseriate (in one row) (native) === D. sophia
Additional aliens: Descurainia incisa (Engelm. ex A. Gray) Britton (N-Am., grain alien).
References
Detling L.E. (1939) A revision of the North American species of Descurainia. Am. Midl. Naturalist 22(3):481-520.
Goodson B.E. (2007) Molecular Systematics and Biogeography of Descurainia Webb & Berthel. (Brassicaceae). Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin. [available online at: http://www.lib.utexas.edu/etd/d/2007/goodsonb02533/goodsonb02533.pdf]
Goodson B.E. & Al-Shehbaz I.A. (2010) Descurainia. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 7. Oxford University Press, New York-Oxford: 460-463.
Goodson B.E., Rehman S.K. & Jansen R.K. (2011) Molecular systematics and biogeography of Descurainia (Brassicaceae) based on nuclear ITS and non-coding chloroplast DNA. Syst. Bot. 36(4): 957-980.
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H.) (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.
Schulz O.E. (1919) Descurainia. In: Engler A. (ed.), Das Pflanzenreich 86(IV.105). Engelmann, Leipzig: 305-346.
Van Landuyt W. (2006) Descurainia sophia. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 337.