Cosmos Cav.
Cosmos is a New World genus of ca. 26 species. It is obviously closely related with Bidens and sometimes included in it. Some species are cultivated as ornamentals in Europe (see Johnstone 2000, Jäger & al. 2008).
1 Ligules orange-red or yellow. Ultimate leaf lobes 2-5 mm wide. Cypselae (fruit) 15-30 mm long, usually hispid === Cosmos sulphureus
Ligules white, pink or purple. Ultimate leaf lobes ca. 1,5 mm wide. Cypselae 7-16 mm long, glabrous-papillose === C. bipinnatus
References
Banfi E., Galasso G. & Bartolucci F. (2018) Nomenclatural novelties for the Euro+Med flora. Nat. Hist. Sc. 5(1): 53-57. [available online at: http://sisn.pagepress.org/index.php/nhs/article/view/365]
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.
Johnstone S.J.L. (2000) Cosmos. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 658-659.
Kiger R.W. (2006) Cosmos. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 21. Oxford University Press, New York-Oxford: 203-205. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=108151]
Sherff E.E. (1932) Revision of the genus Cosmos. Field Mus. Nat. Hist. 8: 401-447.
Verloove F. & Lambinon J. (2008) Neophytes in Belgium: corrections and adjustments. Syst. Geogr. Pl. 78: 63-79.