An identification key to 128 macrolichen species from Tasmanian rainforest is presented. Additional data on the flora are also included. Five new species, Menegazzia caesiopruinosa P. James, M. confusa P. James, M. inactiva P. James & Kantvilas, M. minuta P. James & Kantvilas and M. subbullata P. James & Kantvilas, are described, and the new combination Leioderma amphibolum (Knight) P. M. Jørgensen & D. Galloway is made.

The genus Psilolechia Massal. is reviewed; four species are accepted, including P. leprosa sp. nov. from copper-rich sites in north-west Europe and Greenland, and P. purpurascens sp. nov. from Tasmania. A hyphomycetous anamorph is described for P. clavulifera, and anomalous forms of P. lucida with a vicarious, Stichococcus photobiont are reported.

Rich collections of foliicolous lichens were made, especially from submontane and montane areas, in the Usambara Mountains of Tanzania during the Usambara Rain Forest Research Project expeditions in 1982, 1984 and 1985. An enumeration of the identified species is provided together with taxonomic, ecological and geographical notes. This first part treats 36 species from the Arthoniaceae, Opegraphaceae and all genera with pyrenocarpous ascomata. New records include 14 species for the Usambaras, eight for Tanzania, and three to Africa. Porina sphaerocephaloides sp. nov., widely distributed in the study area, is described.

The lichen substances of 64 Danish specimens of the Cladonia macilenta bacillaris aggregate were analysed by thin layer chromatography. Nine chemical types were found. The presence of thamnolic acid was not found to be correlated with any of the examined morphological parameters.

Some enzymes, particularly esterases and phosphatases, are commonly variable within lichen populations. Mycobiont cultures of Cladonia cristatella Tuck, were examined electrophoretically in order to determine whether isozymes of these enzymes varied among 12 cultures initiated from single ascospores of the same apothecium. There were significant differences among mycobionts with respect to growth in liquid malt-yeast medium, and there was isozymic variability among them just as there is among intact thalli in natural lichen populations. These results are consistent with the idea that in nature ascospores could participate in the reproductive process. Enzymatic differences within a population may originate from propagules, including sexual ones, which initiate individual thalli.