Cullen Medik. is a member of tribe Psoraleeae, all members of which are characterised by delayed development of floral vasculature, the presence of glands, and uniovulate ovaries. Cullen is distinguished from the other members of the tribe by discontinuous floral vasculature, and glandular, non-beaked fruits. Field work and a morphometric analysis of the Cullen patens -complex including 20 populations collected throughout the eastern half of Australia, indicates that four species, Cullen australasicum , C. discolor , C. pallidum , and C. patens , may be distinguished. A phylogenetic analysis indicates two main clades within Cullen , one including species the stems of which are branched at the base, and one in which the species are unbranched below. Furthermore, this analysis shows Bituminaria to be paraphyletic, Cullen includes 32 known species, 5 of which, C. pogonocarpum , C. leucochaites , C. praeruptorum , C. candidum , and C. corallum are described as new.