Bifora is a small genus of three species, native to the Mediterranean region and Central Asia (Mabberley 2008). Two species are agricultural weeds and have spread relatively far beyond their original distribution range. The American Bifora americana (DC.) Benth. & Hook. f. ex S. Watson is not even remotely related to the Old World species of Bifora and in fact belongs in the genus Atrema DC. (as A. americanum DC.) (Hardway & al. 2004).
Members of Bifora have a very distinct smell that reminds of that of Coriandrum sativum and both genera are otherwise also superficially similar. However, in Bifora seeds are obviously didymous (two spherical mericarps attached by a small commissure). In Coriandrum petals are deeply lobed while they are at most obcordate in Bifora.
Molecular studies confirm the close relationship of these genera (Downie & al. 1998)
1 Petals of marginal flowers much longer than the others. Lobes of upper leaves filiform, ca. 0,2-0,5 mm wide. Rays (3-) 4-8. Style 1-1,5 mm long, much longer than the stylopodium === Bifora radians
All petals subequal. Lobes of upper leaves linear, 0,7-1 mm wide. Rays (1-)2-3(-5). Style ca. 0,1-0,2 mm long, +/- as long as the stylopodium === B. testiculata
Brummitt R.K. (1983) Report of the Committee for Spermatophyta: 25: 5956 Bifora G.F. Hoffmann (Umbelliferae). Taxon 32(2): 283.
Downie S.R., Ramanath S., Katz-Downie D.S. & Llanas E. (1998) Molecular systematics of Apiaceae subfamily Apioideae: phylogenetic analyses of nuclear ribosomal DNA internal transcribed spacer and plastid rpoC1 intron sequences. American Journal of Botany 85: 563-591. [available online at: http://www.life.illinois.edu/downie/AJB1998.pdf]
Hardway T.M., Spalik K., Watson M.F., Katz-Downie D.S. & Downie S.R. (2004) Circumscription of Apiaceae tribe Oenantheae. S. African J. Bot. 70: 393-406. [available online at: http://www.life.illinois.edu/downie/Hardway.pdf]
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.