Odontites Ludw.
Odontites is a genus with 32 species, all confined to the Old World (W and S Europe, the Mediterranean area and further east to the Himalayas). A single species is native in Belgium, O. vernus (Bellardi) Dum. (subsp. vernus and subsp. serotinus Corb., the latter being the most widespread) (Lambinon & Verloove 2012).
The generic limits of Odontites are uncertain. Rothmaler (1943), followed by Bolliger (1996) in his monographic study, segregated several small genera (Bartsiella Bolliger, Bornmuellerantha Rothm., Macrosyringion Rothm. and Odontitella Rothm.) and this taxonomic framework was followed by most subsequent floras (e.g. Benedí & al. 2009, Tison & de Foucault 2014). Recent molecular studies, however, suggested that Bartsiella and Bornmuellerantha should be reintegrated into Odontites s.l. (Scheunert & al. 2012, Gaudeul & al. 2016, Gaudeul & al. 2018). All taxa encountered in Belgium, native as well as introduced, belong to Odontites s.str.
1 Corolla pinkish purple (native) === Odontites vernus
Corolla yellowish, sometimes slightly suffused with pink == 2
2 Anthers perpendicular to the filament. Corolla bright yellow. Floral bracts with entire margins === O. luteus
Anthers at right angle to the filament. Corolla pale yellow, often suffused with pink. Floral bracts with a few dents or nearly entire === O. jaubertianus (var. jaubertianus)
References:
Benedí C., Rico E., Güemes J. & Herrero A. (eds.) (2009) Scrophulariaceae. In: Castroviejo S. (ed.), Flora Iberica, vol. 9. Real Jardín Botánico, Madrid: 44-539. [available online at: http://www.floraiberica.es/PHP/familias_lista_.php?familia=Scrophulariac...
Bolliger M. (1985) Die Drüsenhaare der Gattung Odontites Ludwig (Scrophulariaceae) und ihre systematische Bedeutung. Bot Jahrb. 107(1-4): 153-175.
Bollinger M. (1993) Systematik und Chorologie der Gattung Odontites Ludwig s.l. (Scrophulariaceae). Flora, Morphol. Geobot. Oekophysiol. 188: 345-365.
Bolliger M. (1996) Monographie der Gattung Odontites (Scrophulariaceae) sowie der verwandten Gattungen Macrosyringion, Odontitella, Bornmuellerantha und Bartsiella. Willdenowia 26: 37-168. [available online at: http://www.bioone.org/doi/pdf/10.3372/wi.26.2603]
Bollinger M. & Wick L. (1990) The pollen morphology of Odontites (Scrophulariaceae) and its taxonomic significance. Pl. Syst. Evol. 173: 159-178.
Gaudeul M., Siljak-Yakovlev S., Jang T.-S. & Rouhan G. (2018) Reconstructing Species Relationships within the Recently Diversified Genus Odontites Ludw. (Orobanchaceae): Evidence for Extensive Reticulate Evolution. Int. J. Pl. Sc. 179(1): 1-20. [available online at: https://www.journals.uchicago.edu/doi/full/10.1086/694763]
Gaudeul M., Véla E. & Rouhan G. (2016) Eastward colonization of the Mediterranean Basin by two geographically structured clades: The case of Odontites Ludw. (Orobanchaceae). Mol. Phylogenet. Evol. 96: 140-149. [available online at: https://www.researchgate.net/publication/288917746_Eastward_colonization...
Lambinon J. & Verloove F. (avec coll. Delvosalle L., Toussaint B., Geerinck D., Hoste I., Van Rossum F., Cornier B., Schumacker R., Vanderpoorten A. & Vannerom H.) (2012) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Sixième édition. Jardin botanique national de Belgique, Meise: CXXXIX + 1195 p.
Michalková E. (1997) Contribution to taxonomy of genus Odontites Ludw. (Scrophulariaceae) in Slovakia (in Slovak). Bull. Slov. Bot. Spol. Bratislava 19: 4-11.
Pinto-Carrasco D., Scheunert A., Heubl G., Rico E. & Martínez-Ortega M.M. (2017) Unravelling the phylogeny of the root-hemiparasitic genus Odontites (tribe Rhinantheae, Orobanchaceae): Evidence for five main lineages. Taxon 66(4): 886-903.
Rothmaler W. (1943) Die Aufspaltung von Odontites Hall. ex Zinn. Mitth. Thüring. Bot. Vereins, ser. 2, 50: 224-230.
Scheunert A., Fleischmann A., Olano-Marín C., Bräuchler C. & Heubl G. (2012) Phylogeny of tribe Rhinantheae (Orobanchaceae) with a focus on biogeography, cytology and re-examination of generic concepts. Taxon 61(6): 1269-1285. [available online at: https://www.researchgate.net/publication/281691099_Phylogeny_of_tribe_Rh...
Schneider U. (1964) Die Sippen der Gattung Odontites in Norddeutschland. Feddes Repert. Spec. Nov. Regni Veg. 69: 180-195.
Snogerup B. (1982) Host influence on northwest European taxa of Odontites (Scrophulariaceae). Ann. Bot. Fenn. 19: 17-30.
Snogerup B. (1983) Northwest European taxa of Odontites (Scrophulariaceae). Acta Bot. Fenn. 124: 1-62.
Snogerup B. (1987) Släktet Odontites, rödtoppor, i Sverige. Svensk Bot. Tidskr. 81: 145-153.
Tison J.-M. & de Foucault B. (coord.) (2014) Flora Gallica. Flore de France. Editions Biotope, Mèze : xx + 1196 p.