Tithonia Desf. ex Juss.
Tithonia is a New World genus and counts 11 species. All are distributed in Central America, Mexico and the adjacent parts of the United States (La Duke 1982). At least two species of Tithonia are widely cultivated as ornamentals: T. diversifolia (Hemsley) A. Gray and T. rotundifolia (Mill.) S.F. Blake (Knees 2000, Jäger & al. 2008). The latter has been recorded as an alien in Belgium.
Literature:
Blake S.F. (1921) Revision of the genus Tithonia. Contrib. U. S. Nat. Herb. 20(10): 423-436. [available online at: http://biodiversitylibrary.org/item/13780#page/454/mode/1up]
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Knees S.G. (2000) Tithonia. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 656-657.
La Duke J.C. (1982) Revision of Tithonia. Rhodora 84: 453-522. [available online at: http://www.biodiversitylibrary.org/item/24160#page/454/mode/1up]
La Duke J.C. (2006) Tithonia. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 21. Oxford University Press, New York-Oxford: 138-139. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=133067]
Schilling E.E. & Panero J.L. (1996) Phylogenetic Reticulation in Subtribe Helianthinae. Am. J. Bot. 83(7): 939-948. [available online at: http://www.bio.utk.edu/schilling/Helianthinae/genera/Simsia/AJB_83_939_1...
Zardini E.M. (1974) Dos compuestas del genero Tithonia adventicias, nuevas para la flora jujena. Darwiniana 18(3-4): 421-424.