A lichenlogical excursion in May 1997 near Han-sur-Lesse and Saint-Hubert, with notes on rare or critical taxa of the flora of Belgium and Luxembourg

The "Bryologische Lichenologische Werkgroep" of the "Koninklijke Nederlandse Natuurhistorische Vereniging" organized a field meeting in May 1997 near Han-sur-Lesse and St-Hubert in southern Belgium. This paper presents the results of the ecological and taxonomical observations on lichens and their lichenicolous fungi, in the prospect of an "Annotated checklist" currently in preparation for Belgium and Luxembourg. The visited localities include several very important sites, especially the Xerobromion communities near Han-sur-Lesse and the old-growth forest of St-Michel. Pseudorohillarda peltigerae Diederich sp. nov. is a new lichenicolous fungus growing on Peltigera rufescens. The following species are reported as new for the studied area (Belgium and G. D. Luxembourg): Agonimia opuntiella, Bacidia carneoglauca, Bacidia circumspecta, Bacidia herharum, Bacidia trachona, Bagliettoa haldemis, Biatora meiocarpa, Caloplaca alociza, Caloplaca flavocitrina, Cercidospora epipolytrupa, Clypeococcum epicrassum, Dactylospora parasitica, Endocarpon pallidum (the earlier record refers to E. pusillum), Lepraria borealis, Lepraria nivalis, Leptorhaphis maggiana, Libertiella didymospora, Merismatium discrepans, Phaeophyscia cernohorskyi, Pharcidia parvipuncta, Physalospora lecanorae, Polycoccum marmoratum, Polycoccum opulentum, Porocyphus rehmicus, Rinodina pityrea, Staurothele guestphalica, Stigmidium cerinae, Strigula affinis (the earlier record refers to S. jamesii), Syzygospora physciacearum, Toninia athallina, Toninia philippea, Verrucaria funckii and Weddellomyces epicallopisma. The following ones, either very rare or not recorded recently, have been collected: Buellia venusta, Caloplaca lucifuga, Chromatochlamys muscorum var. muscorum, Collema occultatum, Gyalecta truncigena, Micarea pycnidiophora, Naetrocymhe fraxini and Phaeographis inusta. Caloplaca flavocitrina is shown to be distinct from Caloplaca citrina and to be an ubiquitous species in the studied area. The following combinations are introduced : Woessia arnoldiana (Koerb.) Serus. and Diederich (= Bacidia arnoldiana Koerb.), Woessia caligana (Nyl.) Serus. and Diederich [= Bacidia caligans (Nyl.) A. L. Sm.], Woessia delicata (Larbal. ex Leight.) Serus. and Diederich [= Bacidia delicata (Larbal. ex Leight.) Coppins] and Woessia inundata (Fr.) Serus. and Diederich [= Bacidia inundata (Fr.) Korb.]. An albino form is reported for the first time in Opegrapha varia.