Centaurea vlachorum (Asteraceae) in the Balkan Peninsula

Centaurea vlachorum is a Balkan serpentine endemic first described in 1981 from Northern Pindhos (Greece). It was later discovered on two serpentine massifs in Northern Albania. Additional localities for Greece, Northern and Southern Albania are now presented. This species is a taxonomically isolated member of Centaurea sect. Jacea; however, placement in this section is anomalous as bract morphology is more similar to that in C. sect. Cyanus. Whilst examining material in the Halácsy herbarium (WU-Hal), a specimen of C. vlachorum was identified. It had been collected in 1908 by Mihail Dimonie (1870–1935) from the Jablanica Mts on the border of Albania and North Macedonia. Together with the specimen we found an unpublished manuscript in Latin and German, handwritten by Eugen von Halácsy (1842‒1913) which clearly indicates his intention to describe it as ‘Centaurea scabrida’ (sect. Cyanus), on account of its scabrid leaves. This manuscript is here presented. This discovery highlights the importance of the rarely consulted historical collections of Halácsy. They comprise c. 100,000 specimens from all over Europe (Halácsy Europaeum) and c. 26,000 from Greece (Halácsy Graecum), including gatherings by the most important botanists collecting in the Balkan Peninsula in the late 19th and early 20th century. More than 1,500 type specimens in WU-Hal originating from this area have already been databased and photographed with the data openly available on jacq.org.