Belonia pellucida sp. nov. is described from coastal scrubland in North Island, New Zealand. This is the third report of the genus Belonia(Gyalectales) from the Southern Hemisphere. Belonia mediterranea is reported for the second time, from Mallorca.

Porina radicicola sp. nov. is described from Washington, U.S.A. and British Columbia, Canada.

Lichens are troublesome organisms for taxonomists because of their special ‘ double nature ’ i.e. being composed (normally) of two partners. Only recently has it been understood properly that the same fungus can take different photosynthetic partners and develop into quite different-looking organisms, for example Lobaria amplissima and Dendriscocaulon umhausense. The taxonomic problem is to show that two totally different-looking lichens in fact contain the same fungus. This is possible to demonstrate when mixed stands are available, but is now best done with molecular methods. Since the international code of nomenclature rules that the name of a lichen species is the name of the fungus, two different organisms with the same fungus must under the Code carry the same name, which is most impractical. To remove this unintentional complication, one must either make an exception in the Code for these cases, or establish an informal system to take care of them. The latter seems to be preferable.

The different views on the taxonomic use of chemical characters in lichenology are reviewed using the opposing opinions of W. L. Culberson and Rogers and the somewhat intermediate position of Hawksworth as examples. The differing significance of secondary metabolites is illustrated with two examples in the genus Lecanora. In L. campestris and similar species, the chemistry has been useful to differentiate morphologically similar species, which subsequently were found to differ in minute anatomical differences as well. However, in L. caesiorubella, a remarkable chemical variation can be observed that is not correlated with other differences and is thus interpreted as intraspecific variation. An a posteriori valuation of the taxonomic significance of metabolic data is preferred.

Sarcogyne angulosa C. W. Dodge & G. E. Baker, described as an endemic from continental Antarctic localities, is reduced to synonymy with S. privigna (Ach.) A. Massal., a species known from Europe, North America, North Africa and Saudi Arabia, and now Antarctica. The relationship to Polysporina simplex (Davies) Vězda is discussed. It is suggested that the name Sarcogyne grisea Dodge, also described as an Antarctic endemic, should be abandoned. Sarcogyne medusula Dodge is transferred to Lecidea [Lecidea medusula (C. W. Dodge) Hertel comb, nov.], a Maritime- and Subantarctic species.

Morphogenesis of podetia in Cladonia subcervicornis is a non-linear, repeating process based upon a pattern of meristem enlargement and division. Variability in mature podetia of C. subcervicornis, which may appear branched or scyphoid, is the result of variation early in ontogeny. The growth pattern of C. subcervicornis represents a continuum of developmental stages. It is impossible to predict the form of the mature thallus of C. subcervicornis because growth in this species is fluid. The morphology of the mature thallus of C. subcervicornis is difficult to circumscribe using conventional Cladonia terminology, because the processes that form the thallus are dynamic and heterogeneous. The meristem shapes that are produced during early ontogeny in C. subcervicornis are relatively simple, and the processes by which they are formed are uncomplicated. Yet podetial form in C.subcercicornis is difficult to interpret.

The quantitative response to two lichen metabolites, vulpinic acid and (+) usnic acid, on biomass production by the photobiont Trebouxia irregularis, isolated from the lichen Cladina mitis, was determined experimentally. The presence of usnic acid resulted in inhibition of photobiont growth, and the effect depended on the pH of the culture medium. The concentration effect of usnic acid was observed. The application of vulpinic acid almost completely inhibited the growth of T.irregularis and no significant differences were found among samples at different medium pH values.

New sequences have been produced of the ITS rDNA region of twenty-nine species of Parmeliaceae and analysed by neighbour-joining maximum likelihood distance analysis, and maximum parsimony analysis. Twelve monophyletic groups have been identified, most of which correspond to proposed generic segregated from Parmelia s. lat. Parmelia and Parmelina, Melanelia, and Punctelia appear as independent monophyletic groups; the type species of the two latter genera were, however, not included in the analysis. The parsimony analysis does not support Xanthoparmelia as a monophyletic group separate from Neofuscelia, and Rimelia reticulate is nested within Parmotrema. Parmelinopsis horrescens is more closely related to Hypotrachyna revolute than to Parmelina. Genetic distance values suggest that Flavoparmelia caperata is closer to Parmotrema than to other taxa included, and that Platismatia glauca and Hypogymnia tubulosa are closer to Parmelia s. lat. than to the Physciaceae. However, there is no conclusive support for any of thelatter groupings in the parsimony analysis. We conclude that the ITS region contains valuable information for studying generic delimitations within the family Parmeliaceae, but our study suggests that this region will not conclusively resolve within-family relationships in this group.

Water extracts from Nephroma arcticum were prepared and tested for inhibitory effects against various yeast, mould, blue-stain and rot fungi. A water extract from Peltigera aphthosa was used as a reference. Two different diffusion assays were used, wells (cupplate method) and droplets (drop-plate method). For the majority of fungi studied using the former method there were clear zones with a sharp boundary (fungicidal effect), whereas the latter method yielded more or less hazy zones with inhibition or reduction in growth (fungistatic effect). No clear or hazy zones were seen with the extract from P. aphthosa. For Candida glabrata E, Saccharomyces cerevisiae K and Hormonema dematioides S there were clear zones for both methods. The MIC (Minimum Inhibitory Concentration) values were determined in liquid medium for S. cerevisiae K and C. glabrata E and were, respectively, 1 and 10 mg ml−1 of a crude extract from N. arcticum. The MFC (Minimum Fungicidal Concentration) values were found to be identical to the MIC values.

A phylogenetic analysis is presented, based on 57 morphological, anatomical, chemical and ecological characters, including 19 species from the genera Arthonia, Arthothelium and Syncesia. The aim of the study was to test the monophylyof some of the groups within the genus Arthonia suggested, for example, by Redinger (e.g. species with reddish ascomata, with grey-pruinose ascomata and with brown-black hypothecia). The results strongly support that Arthonia and Arthothelium are paraphyletic genera. The best-supported node contains all Arthonia species together with A. crozalsiana de Lesd., A. ruana A. Massal. (both hitherto placed in Arthothelium) and Syncesia myrticola (Fée) Tehler. A well-supported clade is formed by a group of pioneer species, often non-lichenized or poorly lichenized, including the type species of Arthonia, A. radiata. The species with reddish and/or K+ reddish ascomata form one clade and the species with more or less brownish or blackish hypothecia form another clade with Syncesia myrticola, the sister group to the Opegraphaceae and Roccellaceae. The results are discussed and compared with Redinger' grouping. Relationships to other genera within Arthoniaceae are briefly discussed. Arthothelium scandinavicumi Th. Fr., Arthonia dispersa (Schrad.) Nyl., A. punctiformis Ach. and A. mediella Nyl. are lectotypified.

A first hypothesis for the phylogeny of Lecanora subgen. Placodium is presented by using molecular data. Previous evolutionary ideas and classification concepts for this group with non-molecular data are re-investigated using DNA sequence data from the nuclear ITS and 5.8S regions. Using Protoparmelia as an outgroup, the Lecanora subfusca group together with the L. rupicola group appear as a sister group to assemblages with lobate species. Subgen. Placodium as currently accepted, is not monophyletic. Molecular data suggest that the Lecanora dispersa group and the L. polytropa group are widened by lobate species and there is evidence from the ITS data that the monotypic genus Arctopeltis Poelt is closely related to the L. dispersa group. A congruence between molecular data and secondary chemistry supports the broader concept of the L. dispersa group suggested by the molecular data.

After a brief historical survey, some current trends in the delimitation of lichen genera are discussed. A widespread tendency is that of elevating any supposedly monophyletic group of species to genus rank. As the term ‘ monophyletic ’ has no lower limit, this is likely to result in an explosive inflation of new genera, in a severe loss of the information carried by generic names and in a high degree of nomenclatural disorder. Five criteria are proposed for the acceptance or rejection of new generic segregates: (1) DNA testing for monophyly, (2) phylogenetic analysis, (3) number of characters used, (4) number of species considered, (5) information content of the new splittings. Upon a critical analysis of several recent generic segregations, a more flexible approach to taxonomic ranks is recommended, and particularly, when most of the suggested criteria are not fulfilled, a more frequent use of the subgeneric rank, which does not imply name changes.