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.

Lichen communities at four sites of copper sulphide mineralization and associated secondary oxidation products are described from an old mining area at Coniston in the English Lake District. Five lichen species new to Britain, Stereocaulon symphycheilum, Lecanora handelii, Rhizocarpon furfurosum, Lecidea atrofulva and L. inops, are briefly described, the last mentioned being a specific indicator of copper mineralization. The species complex, Lecidea auriculata, L. diducens and L. inops, is discussed in some detail. Toninia leucophaeopsis and the non- British Bilimbia tornensis are distinct species and are both referred to the genus Stereocaulon.

119 investigated Quercus trunks and 67 species of lichens, 23 bryophytes and 3 non-lichenized fungi are arranged by means of the Minimum Spanning Tree analysis, resulting in four Lobarion communities and one Parmelion community. Lobarion is restricted to bark with pH > 5.0 in old forests. pH and Ca-content in the bark are strongly correlated; Ca seems to originate from Ca-uptake through the roots of the phorophyte. Within a single site the soil also seems to be responsible for the variation in the Mg-content of the bark, being correlated with Ca. The dominating source of the regionalvariationinMg, however, seems to be marine aerosols. Parmelion caperatae occurs on acid bark of young trees. The bark is, however, rich in Mg. Soluble tannins in the bark decrease with increasing age of the phorophyte, but are probably of minor significance for the epiphytic vegetation.

The examination of the surface deposit of various lichens with X-ray diffraction methods, correlated with scanning electron microscopical (SEM) studies, have shown that calcium oxalate is present as two different hydrates; weddellite (CaC2O4-(2 + x)H2O), in three slightly different morphologies, and whewellite (CaC2O4H2O). The reason for the formation of calcium oxalate is not known and the presence of the various crystal forms is yet to be explained. However, the various hydrates may have some role in the water balance as they are different in dry and humid sites.

Where two crustose lichen thalli meet at a ‘ truce ’ boundary theshape of the boundary can be used to evaluate models of how lichen growth rates change with thallus size. The application of this method to studies of intra- and interspecific competition are discussed.

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.

Synthetic thalli of Usnea strigosa produced the same fibril morphology and secondary compounds as natural thalli. The outer cortex of synthetic lichens was covered with crystals of usnic acid and compounds related to norstictic acids. The common presence on the fibrils of lichen acids suggests that these compounds have a functional role in the symbiosis. During alcohol dehydration, crystals of usnic acid dissolved and left impressions in the mucilage around the symbionts. The impressions were valuable indicators of the position of crystals in the lichen thallus. Crystal impressions of usnic acid were common on the cortical hyphae and were seen also on the surface of algal cells. The crystal impressions were larger in the synthetic lichen than in natural thalli. Impressions of norstictic acid and related compounds were not seen.

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.

The growth and development of several lichens under natural conditions are studied with the SEM. The results permit observations on the influence of the microclimate and of pollution on thalline development and on some principles of lichen systematics.

The endemic African lichen Parmelia hottentotta (Ach.) Ach. and related species are placed in a new genus, Xanthomaculina Hale, on the basis of cortical chemistry and a combination of conidial and morphological characters, including umbilicate growth form, presence of cilia and a vaulted cortex.

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.

The lichen flora was sampled at each of the five sites on a near-vertical gneiss rock face. The sites were ranked according to the degree ofweathering of the rock surface and were taken to represent different stages in a succession. The succession shows an increase in species richness and diversity over time, although the proportion of the rock face unoccupied by lichens increases at the oldest site. The succession will be driven by allogenic processes, physical weathering of the rock, facilitation, especially the effects of lichens on surface erosion, and by inhibition, through competition for space. At the oldest site mortality of lichen thalli becomes important, continually opening up new areas for recolonization and maintaining community diversity. The succession may be described by four phases: (1) colonization, (2) growth,(3) competition and (4) senescence.

The Southern Hemisphere genus Psoromidium Stirton (Lecanorales, Pannariaceae) is closely related to certain elements within the heterogeneous genus Psoroma Michx, but is distinguished by the absence of a photobiontin the apothecial margin. In Psoromidium, as in Psoroma, the main photobiont is green and is present in a layer below the upper cortex of the squamules; Nostoc occurs in scattered, well-defined cephalodia. Two species are known: P. aleuroides, with an Australasian distribution, and P. versicolor, anaustral species from Tasmania, Fuegia and the subantarctic Auckland Islands group of New Zealand. Anatomy, morphology, distribution, habitat ecology and taxonomy of the two species are discussed. Psoromaria Nyl. is a synonym of Psoromidium.

A new saxicolous genus and species, Glyphopeltis eburina Brusse, is described from southern Africa. The genus differs from Lecidea s. lat. in the peltate thallus.

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.

Lichenostigma rugosa sp. nov. is reported from Europe, North Africa, Asia and the USA. Only one species of Lichenostigma, L. maureri, from Europe and Asia, was previously known. L. rugosa differs chiefly in having spores with deep irregular fissures. L. maureri is reported for the first time from South America (Argentina, Peru), the British Isles and Sweden.

A third fascicle of a lichen exsiccata containing species of Caliciales has been issued; 24 species from New Zealand arc included. Remarks on taxonomy, chemistry, ecology and distribution are given here. Detailed descriptions of Calicium cryptocroceum Tibell, Coniocybe amabilis Tibell and Sphaerophorus notatus Tibellare provided. In addition to the three species described as new in the schedae, Calicium glaucellum Ach., Chaenotheca brunneola (Ach.) Müll. Arg., C. carthusiae (Harm.) Lettau, C. ferruginea (Turnerex Sm.) Migula, C. hispidula (Ach.) Zahlbr., C. stemonea (Ach.) Mull. Arg., Chaenothecopsis debilis (Turner & Borrer) Tibell, C. lignicola (Nádv.) A. Schmidt, C. pusilla (Flörke) A. Schmidt, C. savonica (Räs.) Tibell, C. viridireagens (Nádv.) A. Schmidt, Microcalicium arenarium (Hampe ex Massal.) Tibell, and M. disseminatum (Ach.) Vain, are reported new to the Southern Hemisphere; Chaenotheca trichialis (Ach.) Th. Fr., Coniocybe gracillima Vainioand C. sanguinea Tibell new to Australasia and Microcalicium conversum Tibell and Mycocalicium subtile (Pers.) Szat. new to New Zealand.

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.

Under favourable climatic conditions the mycobiont of Coniocybe furfuracea bears masses of conidia in chains on macronematous conidiophores. The same type of conidia were also formed by axenically grown mycobionts which had been isolated from single ascospores. Germinating conidia were found on the thalli. Coniocybe furfuracea is one of the very few lichen mycobionts so far known with a teleomorph and hyphomycetous anamorph.

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.