Cetrelia cetrarioides (Delise) W.L. Culb. & C.F. Culb.

(Figs 1C; 2; 5A; 6; 7; 12)

It is characterised by the presence of atranorin, perlatolic acid (major), ± imbricaric acid (minor) and anziaic acid. The lack of 4-O-demethylimbricaric acid is obvious and well observable already under UV 254 nm after developing the HPTLC plate (Fig. 2). Its soredia are fine [25-35(-40) µm in diam. – Obermayer & Mayrhofer (2007)], 32.3 ± 3.4 µm in Hungarian samples. Not or slightly raised pseudocyphel - lae of various size (c. 30-300 µm) occur on upper cortex, smaller ones on lower cortex. Its specimens were found most frequently on oak ( Quercus sp. – 38%), beech ( Fagus sylvatica L. – 15%) and other tree species (46%) at lower elevations than in Austria (Obermayer & Mayrhofer 2007), mostly at 200-600 m a.s.l., though in Belarus it occurs at even lower elevation (Bely et al. 2014). This species proved to be less frequent than expected (Figs 6; 7), and was previously confused with C. monachorum . Cetrelia cetrarioides is considered here as a critically endangered (CR) species in Hungary.