The thallus structure of a common epiphytic lichen Hypogymnia physodes growingon the bark of Pinus sylvestris under a variety of microclimatic conditions was studied by means of fluorescence and scanning electron microscopy. The disparity between the thallus layer thicknesses of specimens growing in different habitats proved to be small though obvious, and differences also appeared in the amount of gelatinous substances in the hyphal cell walls ofthe cortex and algal layer. Furthermore, the occurrence of a pored epicortex of H. physodes at dry sites is reported. The size distribution of the thalli, thallus area and the production of soralia showed a complex interaction with microclimate. Against a background of the microclimatic data collected here, humidity is considered to be the most important factor affecting the anatomy and morphology of the thallus.

The epiphytic lichen vegetation on the trunks of Pinus sylvestris and Picea abies was studied and analysed by canonical correspondence analysis in relation to a number of environmental variables. The distribution and abundance of epiphytic lichen species proved to be dependent on the age of the stand, showing divergent responses in relation to phorophyte species and environmental variables such as acidity of the bark and vertical location on the trunk. The importance of stand age in the pattern of community variation is concluded to be an outcome of interaction between changes in the structure of the tree canopy, microclimate and properties of the bark. The responses of single lichen species to changes in the environment seem to vary considerably, indicating differences in competitive ability and ecological strategy between the species.

The ultrastructure of the symbionts within the algal layer of Lasallia hispamca and Umbilicaria spodochroa has been investigated by applying stereological techniques to quantify cellular organelles and structures. The stereological parameters calculated were volume density (Vv) and surface density (Sv). To obtain these parameters for each cellular structure, a systematic sampling of photographic fields of the algal layer for each sample was utilized.Significant differences between the two lichen species with respect to both symbionts were observed. The cellular structures of the photobiont that differed the most between the two lichen species were the chloroplast, which differed by 15°0, in the Vv values and 25°0, in the Sv values, the pyrenoid (as a whole and in the diameter of pyrenoglobuli) and the mitochondria. With respect to the mycobiont, the vacuolar apparatus was of great importance in characterizing the two species, as was to a lesser extent the protoplast volume occupied by concentric bodies.

Samples of Cladonia mitis were collected from three microhabitats within an open field in eastern Hokkaido, Japan. Two sets of sample thalli were taken in close proximity to geothermal vents and a third from a neighbouring area not directly affected by outgassings. Enzymes were extracted and separated by isoelectric focusing, and multiple enzyme forms of three oxidoreductases, glucose-6-phosphate dehydrogenase, glutamate dehydrogenase and superoxide dismutase, and two hydrolases, esterase and alkaline phosphatase, were examined. Similarities between microhabitats based on electrophoretic results were calculated using Jaccard's similarity coefficient and expressed graphically through the complementary techniques of clustering and ordination. All of the major differences in isozyme patterns between remote samples and those near fumaroles were in the two highly polymorphic enzymes, esterase and alkaline phosphatase. Differences were as great or greater than those between geographically separated conspecific populations of lichens examined previously. In the more sulphurous microhabitats, nine bands were much more frequent and eight much less so than in locations further from the source of gases.