The genus Arthopyrenia is redefined to include only corticolous lichenized or non-lichenized fungi. A key and notes are provided for the 14 species accepted for the British Isles, including three new species, A. carneobrunneola, A. ranunculospora and A. viridescens. Arthopyrenia nilescens is resurrected from synonymy, A. cinereopruinosa is confirmed as occurring in the British Isles, and A. fraxini, A. salicis and A. subcerasi are added to the British list. The following names are lectotypined: Arthopyrenia fraxini Massal. (including f. orbicularis Massal. and f. rufidula Massal.), A. salicis Massal., Verrucaria nitescens Salwey and V. subcerasi Vainio.

The nature of elm bark as a lichen substratum is considered; a method of bark pH measurement is described and examples show the effects of the environment on bark pH. A summary of elm taxonomy includes a field key to the identification of elms. An estimation of the degree of restriction of 97 lichen species found on elms is given together with distribution maps of the most restricted species, and a list of lichens recorded on elm. The spread and control of Dutch Elm Disease is discussed. The future of elms and the consequences for the more highly restricted lichen species are reviewed. Bacidia incompta, Collema fragrans, Gyalecta flotowii, G. ulmi, and particularly Caloplaca luteoalba and Cryptolechia carneolutea, are most at risk from the widespread loss of elms.

Ninety-two specimens (of 26 species belonging to four genera) of the Graphidaceae were collected from various areas in Japan. Their phycobionts were isolated and studied taxonomically. The phycobionts were all identical and identified as Trentepohlia lagenifera, an alga that is widely distributed in Japan. It occurs freeliving on bark and stones under humid conditions. This alga forms zoosporangia abundantly in the field and in culture but not in the lichenized state.

A photosymbiodeme is described for Peltigera venosa. One member consists of small black squamules containing cyanobacteria whereas the other, the more familiar thallus of the species, contains green algae. New aspects of morphogenetic influences are discussed.

Soredia of Peltigera didactyla were cultivated under laboratory conditions in a culture chamber. The developmental stages were observed by light microscopy and macrophotography until thallus formation was achieved; this occurred after a period of five months.

Thalli of five species of epiphytic lichens were collected from one moribund spruce-fir stand in the Algonquin Highlands in Ontario, Canada. Extracts of all were subjected to isoelectric focusing and stained for activity of 16 enzyme systems. Gels were scored for the presence or absence of individual bands in each enzyme system, and the degree of polymorphism of all detectable enzymes was evaluated using a variability measure developed for use with presence/absence data. Esterase and alkaline phosphatase showed the greatest amount of polymorphism and superoxide dismutase was the least variable enzyme system. The degree of enzyme variability in each of the five species was probably a reflection of its past evolutionary history and bore little relationship to apparent potential for sexual reproduction.