Caloplaca maritime B. de Lesd. is a marine to maritime species occurring in western Europe. It was first described as a variety of C. citrina (Hoffm.) Th. Fr., but in 1953 was transferred to specific level. Since then C. maritima has been more or less forgotten and/or misunderstood, mainly due to confusion with C. ruderum(Malbr.) J. R. Laundon, C. interfulges (Nyl.) J. Steiner, and C. marina (Wedd.) Zahlbr. The present paper reports on the existence of C. maritima, and clarifies its status in relation to C. marina and to other related species. A map of the presently known distribution is presented and the species is depicted. Lectotypes for Caloplaca citrine var. maritime and C. citrine var. maritime f. laevigata are selected.

The saxicolous Strigula fractans sp. nov. and S. rupestris sp. now are described from Lord Howe Island, New South Wales, Australia. A new combination, S. decipiens (Malme) P. M. McCarthy, is proposed for Porina decipiens Malme, and a key to the 17 saxicolous species of Strigula is provided.

Melaspilea circumserpens Nyl., hitherto known only from the type specimen, collected in Tasmania in 1803 by Robert Brown, has been rediscovered. The species has proved to belong to the genus Glonium (Hysteriaceac), previously not known to contain species associated with algae. The new combination Glonium circumserpens (Nyl.) Kantvilas & Coppins is proposed. The anatomy, morphology and ecology of the species are described. Problems regarding the provenance of several lichen specimens collected by Robert Brown are discussed.

Intraspecific thallus interactions in mixed populations of Rhizocarpon lecanorinum and R. geographicum in North Wales are described. In contrast to the most commonly occurring morphotype of R. geographicum, which forms mosaics comprised of sharply delimited individual thalli, R. lecanorinum thalli consistently merge with one another at intraspecific contacts, leaving no visible trace of their initial boundaries. On the analogy of mycelial interactions in populations of wood-rotting and other non-lichen-forming fungi, it is postulated that these differences are the outcome, in R. geographicum, of somatic incompatibility between distinct genotypes, and in R. lecanorinum of somatic compatibility among genetically identical or very closely related thalli. Possible mechanisms for the evolution of clonal population structure in R. lecanorinum and links between somatic interactions and reproductive output in these species are discussed. Facultative parasitism of R. lecanorinum by Schaereria fuscocinerea, and resistance to such parasitism by cooccurring R. geographicum, are also documented.

Field emission scanning electron microscopy was used to characterize mycobiont wall surfaces in Umbilicaria hyperborean from Greenland. To determine the precise intrathalline distribution of phenolics, comparisons were made of hyphal surface features and dimensions before and after acetone extraction. Stratification was evident within the medulla, as extracellular phenolics were observed only on hyphae near or within the algal zone. The outside diameter of hyphae in this region was thus significantly greater than in the remainder of the medulla. Surface deposits were also examined in 1350-year-old subfossil thalli and hyphal diameters were compared statistically to those in extant thalli. The mean hyphal diameter in the upper medulla was not significantly less in subfossil specimens than in recent thalli, suggesting that phenolic cover was maintained in spite of glaciation. However, after ice burial phenolic masses tended to be flatter than in recent specimens and finely tubcrculate. The appearance of mycobiont hyphae in the cortex of subfossil thalli seemed to be the same as in extant thalli, except that there tended to be more compressible, smaller and less conglutinated filaments near the algal layer.

Comparisons of whole-lichen physiology to the respective photobionts have often been unclear due to inherent differences in isolated photobiont culturing techniques. The use of 13-mm-diameter cellulose-acetate discs allows photobiont cultures access to nutrient agar medium, while improving ease of manipulation and distinct separation from the agar. Adequate culture growth for experimentation is reached in approximately three weeks, a time comparable to standard nutrient agar and liquid cultures. These discs are then available for use in a variety of manipulative techniques. Chlorophyll determination of an entire algal disc culture is obtainable because the discs readily dissolve in dimethylsulphoxide (DMSO), with no interference in the 400–700 nm range. Photosynthesis and respiration may be measured with standard gas exchange equipment. Photobiont discs allow for fumigation in the gas phase with no increase in external ⊂pH reported to occur during gaseous fumigations in liquid media. The disc system is also useful for fluorescence studies. Trebouxia erici cultures exhibited a CO⊂2 gas exchange on a gram dry weight basis similar to whole lichen systems. The ease with which photobionts can be cultured and manipulated using this system allows for expanded experimentation and comparisons.

A molecular study was undertaken to clarify the identity of the photobiont in colourmorphs of the lichen, Peltigera membranacea. Two strains of cyanobacteria, identified as Nosroc sp. by morphology, were cultivated from each of two lichen specimens. Prokaryotic (16S) ribosomal RNA gene fragments were amplified by the polymerase chain reaction (PCR) from DNA extracted from the isolated strains and the lichens, and sequenced directly. Sequences were 98 1% identical between lichen specimens, TDI#AR94 and TDI#AR95, and highly similar to sequences published, or generated in this study from a type culture, for Nostoc. The 16S ribosomal RNA gene sequences (‘ 16S rDNA’) of all four lichen-derived cyanobacteria appeared the same, even though the lichen specimens from which they originated had different sequences. The 16S rDXA from strains 9A and 9B were different from that of specimen TDI#AR94, the thallus from which they were isolated, and instead were the same as that of strains 10A and 10B, and their source, specimen TDI#AR95. When primers selective for the strain 9A sequence were used, however, a small amount of PCR product corresponding to the 16S rDNA of strain 9A was obtained from lichen TDI#AR94. The results confirm that the photobionts of P. membranacea belong to Nostoc, and suggest that genetic differences in the photobiont may be a factor in the occurrence of colourmorphs among cyanolichens.