The term gomocyst, introduced by Norman in the last century, has been used to designate lichen thalli consisting of algal colonies embedded in a hyphal envelope. It has been applied to the Moriolaceae, ‘Botrydina’ and several groups in the Lecideaceae s. lat. A preliminary survey demonstrates that the concept encompasses different structures. Nevertheless, and ad interim, the term is here used to describe the small diaspores produced by several species of foliicolous Opegrapha in a peculiar organ, the gomocystangium. Four such species are known in Opegrapha: O. dibbemi sp. nov. in Costa Rica, O. lambinoniiSérusiaux in Zaire, O. luzonensis sp. nov. in the Philippines and O. santessonii sp. nov. in Zaire, but foliicolous lichen thalli with goniocystangia are known from undisturbed rain forests at low elevations in four continents.

Two ubiquitous diazotrophic North American lichens, Peltigera aphthosa and P. polydaclyla, were subjected to simulated acid rain. Both lichens exhibited a 50% reduction in nitrogen fixation at pH 5, 80% reduction at pH 4 and complete inhibition at pH 2. Nitrogen fixation was zero after 20 days exposure to simulated rain at pH 3 and zero after fourdays at pH 2.

A regression equation was used to relate apothecium diameter to apothecium dry weight inXanthona parietina. This was used to estimate the contribution of apothecia to thallus weight in 80 randomly selected thalli from vertical concrete posts at Romney, Kent (mean 22–5%, range 0–87%). The energy contents of apothecia and the sterile thallus were found to be similar (17.6—18.2 KJ g−1 dry weight) and apothecium production was found to be independent of thallus aspect. The results are discussed with reference to apothecium growth rates and the allocation of resources in lichens.

37 taxa are discussed, with 34 being new to Madeira. Of these, Gyalectidium filicmum Müll. Arg., Massalongia carnosa (Dickson) Körber, Physaa tnbaaoides Nyl. and Rinodina intermedia Bagl., are first records from Macaronesia. Ecology and distribution of the species are briefly outlined. Our investigation shows that the proportion of both northern temperate and tropical elements in the lichen flora of Madeira is higher than formerly known.

A description and ecological interpretation of lichen communities occurring on high ground in the Cairngorms is presented. The area supports only a limited lichen flora but it is highly specialised; a quarter of the 134 species encountered are thought to have their main area of distribution in Britain on the Cairngorm plateau. The majority of these are associated with areas of late snow-lie from which Cladonia stricta, Lecidea griseoalra, Micarea viridiatra, Sporaslatia cinerea and Staurothele clopima, all new to the British Isles, were discovered together with two species still to be determined. The detailed zonation of lichens round a semi-permanent snow patch was investigated using a transect. Central areas of snow-beds are identified as receiving sites for nutrients and contain a proportion of basiphilous lichens. High wind speeds appear to restrict lichen distribution in certain saxicolous habitats; from several such sitesLecidea nigroleprosa new to Britain was collected. In Funcus trifidus heath and dwarf Calluna the occurrence of lichens is largely determined by the growth and decay of the dominant higher plants.

96 macrolichens, including 12 new records, are reported for cool temperate rainforests in Tasmania. These species belong mainly to the austral cool temperate element. A descriptive account of the lichen floras from five major rainforest communities is given. Field observations suggest that substrate and light are the most important ecological factors affecting the distribution of lichens in rainforest. Although most species are widespread in Tasmania, large-scale disturbance and the fragmentation of rainforest stands is seen as a threat to their survival.

The monotypic genus Wawea gen. nov. is described as a second genus in the family Arctomiaceae. The single species, Wawea fruticulosa sp. nov., is characterized by its fruticose habit, rugose and corticate lobes, secondarily multidivided and coalescing apothecia, two-celled spores, and by the unique initial stage of ascocarp ontogeny which includes simultaneous development of ascogonia as well as short-celled, branched conldiophores producing conidia. W. fruticulosa is widespread in Tasmania and is known also from New Zealand with single collections from the North and South Island. A new pyrenomyceteRhynchomeliola lichenicola sp. nov., parasymbiotic on Wawea fruticulosa, is also described.

A new terncolous Micarea (M. viridiatra sp. nov.) is described from the Cairngorm Mountains. It is similar and apparently closely allied to M. turfosa.

The inhibitory action of aqueous extracts from detached podetia of heathland Cladonia spp. and leachates from transplanted Cladonia turfs was tested using seeds of Avena fatua, Calluna vulgans and Deschampsia flexuosa. Significant inhibitory effects were found for each species. Further evidence from a field experiment suggests that patches containing a mixture of Cladonia spp. can inhibit germination or establishment of vascular species, probably through both chemical and physical processes, and thus maintain intact lichen patches in otherwise closed heathland stands.