Lichen mycobionts are typical representatives of their fungal classes but differ from non-lichenized taxa by their manifold adaptations to symbiosis with a population of minute photobiont cells. Most interesting are the morphologically complex macrolichens, the fungal partner of which competes for space above ground and contains photobiont cells optimally positioned for gas exchange and illumination. Such thalli are the product of an amazing hyphal polymorphism, with multiple switches between polar and apolar growth and hydrophilic or hydrophobic cell wall surfaces. Hydrophobic sealing of the apoplastic continuum between the partners by means of mycobiont-derived hydrophobic compounds canalizes the fluxes of solutes during the often quite dramatic de- and rehydration processes and keeps the algal layer gas-filled at any level of hydration. The impressive tolerance of drought, heat and cold stress of most lichen-forming fungi and their photobionts is due to a very interesting combination of protective and repair mechanisms at the cellular level, the molecular bases of which remain to be explored. Contemporary experimental lichenology is analysed and strategies are proposed aimed at better integration into mainstream biology.

Biatora hertelii Printzen & Etayo and B. troendelagica Holien & Printzen are described as new to science. Diagnostic characters, systematic affinities, ecology and distribution of both species are briefly discussed. Divaricatic acid is reported for the first time from a species of Biatora

A revision of several specimens of Catillaria mediterranea Hafellner revealed that two species can be recognized: C. mediterranea s. str., which has 8–16 spores per ascus, grows on foliose and fruticose lichens, and has a Mediterranean- Macaronesian, montane distribution, and C. praedicta Tretiach & Hafellner sp. nov., which has (16-) 24–32 (-48) spores per ascus, occurs on shrubs in coastal Mediterranean maquis, and has a Mediterranean, maritime distribution. The systematic affinities of the two species with the 8-spored C. nigrodavata (Nyl.) Schuler are briefly discussed.

Immersaria olivacea, its lichenicolous fungus Polycoccum decolorans, and Immersaria mehadiana are described as new species from Spain and Romania, respectively. A new combination, Immersaria cupreoatra is proposed, and a revised concept of the genera Bellemerea and Immersaria is supplied.

Porina radicicola sp. nov. is described from Washington, U.S.A. and British Columbia, Canada.

Sarcogyne angulosa C. W. Dodge & G. E. Baker, described as an endemic from continental Antarctic localities, is reduced to synonymy with S. privigna (Ach.) A. Massal., a species known from Europe, North America, North Africa and Saudi Arabia, and now Antarctica. The relationship to Polysporina simplex (Davies) Vězda is discussed. It is suggested that the name Sarcogyne grisea Dodge, also described as an Antarctic endemic, should be abandoned. Sarcogyne medusula Dodge is transferred to Lecidea [Lecidea medusula (C. W. Dodge) Hertel comb, nov.], a Maritime- and Subantarctic species.

Water extracts from Nephroma arcticum were prepared and tested for inhibitory effects against various yeast, mould, blue-stain and rot fungi. A water extract from Peltigera aphthosa was used as a reference. Two different diffusion assays were used, wells (cupplate method) and droplets (drop-plate method). For the majority of fungi studied using the former method there were clear zones with a sharp boundary (fungicidal effect), whereas the latter method yielded more or less hazy zones with inhibition or reduction in growth (fungistatic effect). No clear or hazy zones were seen with the extract from P. aphthosa. For Candida glabrata E, Saccharomyces cerevisiae K and Hormonema dematioides S there were clear zones for both methods. The MIC (Minimum Inhibitory Concentration) values were determined in liquid medium for S. cerevisiae K and C. glabrata E and were, respectively, 1 and 10 mg ml−1 of a crude extract from N. arcticum. The MFC (Minimum Fungicidal Concentration) values were found to be identical to the MIC values.