Thelidium pluvium sp. nov. is newly described from rocks in streams in Great Britain, Ireland and Norway. It is characterized by perithecia which are partly covered by a thalline layer, a thin involucrellum, and 1-septate spores. A provisional key is given to species of Thelidium in north-west Europe.

Omphalodiella patagonica Henssen gen. et sp. nov. is described from two Patagonian localities in Argentina. In habit the new lichen resembles some species of Acarospora in having brown, peltate thalli less than 3 mm wide with immersed apothecia. The ontogeny and structure of the apothecia and pycnidia correspond, however, to genera of the Parmeliaceae. The apothecia are provided with a meristematic, cupular exciple, and the amyloid asci contain 8 or less, ± globose spores. The short-celled conidiophores produce rod-shaped conidia of bayonet type. The thallus is provided with a narrow paraplectenchymatic upper and a broad prosoplectenchymatic, strongly gelatinized lower cortex. The thallus contains gyrophoric acid; the cortex contains ‘glomellifera brown ’.

The extent to which biotic factors (competition, predation/disease, longevity) regulate lichen community development can be addressed by considering a number of general trends expected in higher plant successions and searching for supporting evidence from lichen studies. Four of the most frequently observed (or predicted) trends during succession are that: (1) superior competitors replace poor competitors; (2) ecologically specialized species replace generalists; (3) chemically well-defended species replace poorly-defended species; (4) long-lived species replace ephemeral species. Available evidence suggests that, for many lichen communities, competitive exclusion rarely occurs once thalli are established. This is especially true for communities that develop on the most stable habitats. An absence of competitive exclusion suggests that lichen successions are driven more by additions of colonists than by species replacements, and replacement trends observed in higher plant successions are therefore observed less frequently inlichen successions.

The terricolous species Verrucaria xyloxena Norm, and V. bryoctona (Th. Fr.) A. Orange comb. nov. are described and figured. Verrucaria sibirica Zahlbr. is described briefly and the interpretation of the name V. velutina (Bernh.) Ach. is discussed.

Anamorphs of 17 taxa in the genus Umbilicaria (Lecanorales, Ascomycotina)a re connected with known teleomorphs through what is described as the thallic type of connection. Teleomorphs of Umbilicaria aprina Nyl. and Umbilicaria cinerascens (Arnold) Frey are described for the first time. Possible correlated trends in the evolution of anamorphs and teleomorphs are discussed.

After a brief historical survey of the developments of vegetation science in general, and of lichen community studies in particular, this paper presents critical comments on some of the main methodological problems in the study of lichen vegetation, with particular regard to the phytosociological approach. It is suggested that in the description and classification of lichen communities lichenologists should avoid the inflation of community names that characterize the present state of the phytosociology of phanerogamic vegetation. This can be accomplished on the basis of a sound methodological approach, where the use of numerical methods can play a major role.

A new species of Lecanora with a yellowish green thallus, Lecanora strobilinoides Giralt & Gomez-Bolea sp.nov. is described. It was found only in SE Catalonia (NE Spain) at low and middle altitudes, growing on bark and lignum of trees and shrubs, mainly on Pinus halepensis and Quercus ilex. Closely related to Lecanora strobilina (Sprengel) Kieffer, it is easily separated by its asci, with (12–)16(–32) ascospores, that are smaller and frequently 1-septate.

In order to obtain a complete picture of the factors determining spatial pattern in a saxicolous lichen community (or any other plant community) it is important to use a range of analytical techniques at a variety of scales. The Jonas Rockslide study is an example of this, and three analyses from this study are discussed here. Each scale gives a different perspective on the processes acting in the community. The largest scale shows that lichen distributions are correlated with attributes of whole rockfaces such as slope and aspect. The second analysis examines pattern at the scale of 10 cm to 20 cm grid points and shows that within a rockface are many micro-habitats, reflected in the pattern of occurrence of different lichen species at this scale. The smallest scale of analysis is a ‘nearest-neighbour’ analysis, which indicates that lichens sample their environment differently and have different ecological strategies. These processes ultimately act together to give the observed pattern in the community.

A sterile, sorediate, corticolous, crustose lichen from Central Sweden is tentatively assigned to the genus Buellia as B. violaceofusca sp. nov. It grows on the bark of old trunks of Quercus robur in moist, dense woods dominated by that tree.

Frequencies of anamorph and teleomorph production in 18 species of Umbilicaria were calculated from field samples and herbarium collections. In one group of species teleomorph production (with sexually generated ascospores) is almost entirely suppressed and compensated for by an abundant production ofanamorphs (asexual thalloconidia). A second group of species exhibits a continuum from exclusively anamorphic through ana-teleomorphic to exclusively teleomorphic individuals. In this group there are distinct biogeographic patterns in the distribution of the teleomorphic individuals. A third group consists of pairs of apparently closely related taxa where one taxon is richly anamorphic and rarely produces teleomorphs, whereas the other taxon is richly and exclusively teleomorphic; this can be referred to as a phylogenetic teleomorph-anamorph relationship. The members of these taxon pairs commonly have different geographical distributions.

Two hundred and three specimens belonging to the genus Cetrelia from the Soviet Union and also 41 samples from other countries have been analysed by TLC. Eight species were determined in the Soviet Union. In addition two new species, C. orientalis and C. pseudocollata sp. nov. are described. Five morphotypes and six chemotypes have been recognized in the genus: their main characteristics are tabulated in a form that can be used for identification and a key is also included. Evolutionary relationships between the ‘primary’ and ‘secondary’ species related to ‘species-pairs’ are discussed.

The resynthesis of foliose thalli of the cyanobacterial lichen Peltigera praetextata was achieved on a soil substratum under laboratory conditions. On agar plates mycelia formation by this lichen fungus only occurred when a sufficient number of photobiont cells was present. Resynthesis on agar was restricted to the formation of loose algal-fungal associations, which showed no lichen-like structures. Early resynthesis stages were formed on soil only after a very long lag phase of 2–3 months. First soredia-like stages (resynthesis products of fungal hyphae and cyanobacteria) appeared, later tissue clumps and thallus primordia differentiated. Welldeveloped lichen thalli with rhizines that resembled young thalli from the natural environment were formed after an incubation time of 2–3 years.

Macentina dictyospora sp. nov. is described from wood of Betula in northern Sweden; it is distinguished from the other members of the genus by the submuriform ascospores.

The distribution of cryptogams and phanerogams and the microclimate of different habitats have been studied. It is shown that a forest community of phanerogams includes an assemblage of different microhabitats inhabited by different lichens and mosses. The distribution of lichens and mosses is governed by factors that are often of little importance to higher plants.

Eighty-seven lichen taxa were collected at four localities near the leadzinc mine at Maarmorilik. These are listed alphabetically and grouped according to their ecological preferences. Lichens, which in Greenland are restricted to calcareous rocks and alkaline soil substrata, are well represented in the Maarmorilik area. In contrast, ferrugineous lichens appear to be comparatively rare. The lichens around the mining town are assumed to have accumulated significant concentrations of airborne lead and zinc. However, no damage to the lichens caused by heavy metals was observed.

Two national monitoring surveys were carried out within 5 years, using Parmelia sulcata as a biomonitor of trace-element air pollution. The method of sampling was standardized. The lichen samples were analysed by neutron activation analysis. Local variations in element concentrations in lichens from various deciduous tree species from several sampling sites were established. The geographical concentration patterns obtained from the lichen data sets agreed with the element concentration gradients obtained from one dispersion model and measured data of atmospheric concentrations and deposition. Comparison of the two lichen data sets showed the relationship of the geographical concentration patterns with time. Combination of the available data gave insight into the possibility of localization of pollution sources.

A new method is described that records the periods of photosynthetic and respiratory activity in lichen thalli in situ by measuring the actinic chlorophyll fluorescence response of the photobiont. The technique is based on a pulse amplitude modulation fluorometer that was specially developed for continuous and unattended measurements in the Antarctic. In Livingston Island, South Shetland Islands, the periods of metabolic activity of Usnea antarctica were recorded simultaneously with the microclimatic parameter in its natural environment. In one series of diurnal measurements the fluorescence response signal was treated as a qualitative on/off signal for photosynthetic activity. In a parallel series the diurnal courses of net photosynthesis and dark respiration of rain-moistened thalli of U. antarctica were measured by means of a CO2/H2O porometer together with gravimetric water content determination. Both methods showed marked coincidence from low water content to water saturation of the thalli. In the laboratory both the actinic fluorescence response and the photosynthetic rate as a function of thallus water content were investigated in Caloplaca regalis. In the laboratory experiments the CO2 exchange cuvette contained a balance for gravimetric water content control as well as the glass-fibre optics of the fluorescence analysis equipment. The experiments revealed a quantitative relationship between actinic fluorescence and photosynthetic rate within the range of optimum to limiting low thallus water content. The method described is suitable for measurements of lichen activity in field microclimate studies and should allow continuous unattended year-round measurements of lichen activity, which are needed in remote regions such as Antarctica.

The sorediate species Hyperphyscia variabilis Scutari from South America is described as new. Its apparent affinities with H. crocata Kashiw.are briefly discussed. The correlation between the type of ascospores (number and disposition of septa) and the geographical distribution of species throughout the genus is stressed, and three species groups are distinguishedon this basis. Two new combination, Hyperphyscia coralloidea (Lynge) Scutari and Hyperphyscia viridissima (Mull. Arg.) Scutari, are proposed.