Bacidia neosquamulosa Aptroot & van Herk, a new corticolous lichen species, is described from the Netherlands, where it seems to be rapidly spreading and where it is considered to be a neophytic species. It is also reported from Belgium and Great Britain. It resembles corticolous morphs of the rather variable B. arnoldiana, but differs from this and other species by the longer, conspicuously septate, filiform, curved, macroconidia, the longer ascospores and the squamuloseisidiate thallus.

Aspicilia crespiana Rico is described as a new species from central Spain and Sardinia (Italy). In central Spain it is common and has a well-defined ecology. It is found at middle to high altitudes (from 400 to 1900 m), overgrowing mosses on exposed and horizontal to more or less vertical siliceous rocks. Closely related to the A. contorta (Hoffm.) Kremp. complex, A. crespiana differs in its muscicolous habit and thallus development, consisting of a network of lichenized squamules interlinked by fungal rhizomorphs.

Pocsia mucronata P. M. McCarthy sp. nov. (incert. sed.) is described from Lord Howe Island, New South Wales, Australia. This foliicolous lichen inhabits leaves of the endemic palm, Howea forsteriana.

A fourth foliicolous species of Anisomeridium is described. Anisomeridium musaesporoides has so far only been found in Guyana and Panama. It is characterized by applanate perithecia with a white marginal zone, large spores with a submedian septum and apical ostiole. A key to all known foliicolous Anisomeridium species is provided.

Thallus organization is examined in Aspicilia californica Rosentreter, fruticose lichen known from several localities in central and southern California. The sprawling, terete thallus branches possess a dense central medulla of thickwalled, longitudinally oriented fungal cells. This central tissue emerges at branch apices to form a darkly pigmented fungal tip. Thallus development involves the apical extension of the tip to produce a fungal tissue over which a cylindrical algal layer and cortex will eventually be formed. Apical branches are initiated by furcation entirely within the fungal tip. Lateral branches, emerging from the lichenized thallus, arise as a divergent bundle of elongate fungal cells originating in the medulla. The photobiont appears to play no direct role in initiation of apical or lateral branches. It is concluded that thallus development in A. californica occurs with a relatively low degree of synchrony between mycobiont and photobiont growth, similar to the pattern observed in crustose lichens with prothallic growth. A rather similar type of thallus organization is observed in A. hispida, although in that species mycobiont growth and branch initiation appear to be somewhat more closely associated with algal cell proliferation. A squamulose Aspicilia from central Spain produces rhizomorphs that may sometimes become invested with an algal layer and cortex, resembling the thallus axes of A. californica.

A survey aimed at studying the effects of hydrogen sulphide (H2S) on epiphytic lichen vegetation was carried out at Acquapassante (Mt. Amiata, Central Italy). In 1992, lichen vegetation was surveyed using a sampling grid often units, on 18 chestnut trees along a transect from a chimney emitting H2S to c. 200 m in the direction of the prevailing winds. A Lichen Biodiversity Index (LBI) was calculated as the sum of the frequencies of all species present within the grid. The same survey was repeated five years later. Concentration Analysis was applied to describe the data structure, and Procrustes Analysis was used to verify the congruence between the ordinations of 1992 and 1997. The statistically significant linear and non-linear regressions found between environmental variables (distance of relevés from the chimney, bark pH, lichen biomass of selected foliose and fruticose species, total sulphur content of Evernia prunastri, Hypogymnia physodes, Parmelia sulcata and Ramalina fastigiata) and the position of the relevé points on the ordination axes suggest that species distribution along the transect is related to differences in H2S tolerance. However, some crustose species (Lecanora cf. conizaeoides, L. saligna and Scolkiosporum umbrinum) should be probably excluded from the computation of the LBI for monitoring purposes, as their optimum is in the immediate vicinity of the H2S source.

Using a sequential elution procedure, the cellular location of Cl−, Na+, Mg2+, K+ and Ca2+ was determined in the lichen Ramalina canariensis from the southwest coast of Portugal. After a dry deposition period, a logarithmic decrease in the extracellular (surface and wall-bound) concentration of Cl−, Na+ and Mg2+ was observed with increasing distance from the coast. The importance of each cellular fraction as an indication of the airborne salts was identified using factorial analysis methods, as was the relationship between the extracellular and intracellular concentration of the saline elements. The factorial analysis showed that the most important elements for the biomonitoring of airborne salinity were Cl−, Na+ and Mg2+. However, for the cations, only the surface and wall-bound (for Na+) fractions seem to be related to sea-salt deposition on the lichens. The intracellular fractions of these elements are relatively independent of the surface and wall-bound concentrations, or reflect some non-linear processes induced by extreme extracellular concentrations. Although they may represent a significant proportion of the total element concentration, intracellular element concentrations are of little value in monitoring salt deposition, due to physiological control by the organism. The use of total analyses, without any fractional differentiation, can be a biased method for biomonitoring the accumulation of salt spray by lichens, because it includes the intracellular fraction, which may be independent of the deposition taking place. The use of the different cellular fractions provides a more informative indication of the deposition of atmospheric elements, while also giving information on any physiological alterations induced by the specific environmental chemical factors, including membrane damage.