The morphology, anatomy, chemistry, habitat and distribution of eight southern-Huropean sorediate, blastidiate or isidiate species of the genus Rinodina are treated. One species, R. nimisii, from Corsica and Sardinia, is new to science. Rinodina erysiphaea, R. sorediata and R. sipmanii are synonyms of R. colobinoides. A key is provided. Other known sorediate, blastidiate or isidiate species arc briefly discussed.

Descriptions and a key for identification of lichenicolous Arthonia species with red to purple pigments reacting with K are provided. The previously reported species, A. cryptotheciae and A. mazosiicola (as A. mazosiae), are here validly described, and A. haematostigma, A. tavaresii and A. destruens var. nana are new to science. The genus Helicobolomyces is introduced with the type species H. lichenicola, being based on the anamorph of A. cinnabarinula.

Examination of specimens of Peltigera didactyla, from Africa, Asia, Europe and North America revealed that this sorediate species includes three entities that can be separated on morphological characters. A new species, P. lambinonii, is described from East Africa, and a new combination P. didactyla var. extenuata, is proposed to accommodate morphs from mesic forest habitats in Asia, Europe and North America. Despite this taxonomic reduction, P. didactyla var. didactyla remains a ubiquitous taxon. The former two taxa often produce methyl gyrophorate, which can co-occur with traces of gyrophoric acid. These tridepsides were only rarely detected in var. didactyla; their occasional presence seems to be best explained by hybridization. The taxonomic and ecological significance of these substances is discussed.

Lobaria pulmonaria and other members of the Lobarion were found to inhabit drainage channels below old and large wounds on the trunks of various deciduous trees in stands of long ecological continuity in a forest reserve dominated by Picea abies in southeastern Norway. Such channels were richer in minerals and had a higher pH than normal bark, which was covered with more acidophytic epiphytic communities, mainly the Pseudevernion. Chemical microhabitat differentiation was most clear in edaphically poor sites. The restriction of a previously ubiquitous Lobarion to mineral-rich microsites on stems is probably an effect of acid rain. Since acidification seems to make the Lobarion more dependent upon old and damaged stems, modern forestry probably aggravates the damage caused by acid rain.