Bituminaria plumosa (Fabaceae), a critical species of the Croatian flora

Background - Bituminaria is a small genus of the family Fabaceae that belongs to the tribe Psoraleeae distributed both in the Mediterranean and Macaronesian region. In the framework of taxonomic research on this genus, an unresolved species described from Croatia, and previously attributed to Psoralea, is here restored and properly transferred to Bituminaria, thus proposing a new combination. Methods - Field investigations, herbarium specimens, morphological analyses and literature were used for a correct identification of this species and its comparison with the other known taxa of the genus Bituminaria. Results - Bituminaria plumosa (Rchb.) Bogdanovic, C. Brullo, Brullo, Giusso & Ljubicic (= Psoralea plumosa Rchb.), originally described from Istria (North Croatia), is recognized as a distinct species of this peculiar genus. Considerations on its morphological features, seed testa micro-sculptures, ecology, chorology, taxonomical relationships, as well as a new and detailed iconography are provided. This species is morphologically well distinct from the other known species of the genus in having a densely villous indumentum, with very long hairs, leaf petiole very short, leaf blades ovate to ovate-lanceolate, long aristate, corolla purplish-pink, standard elliptical, long pistil, and large seeds.