The new generic names Metamelanea Henssen and Strotnatella Henssen are described inthe Lichinaceae. They are denned by the developmental morphology of the ascocarp and thallus structure. In both genera the thallus is subfruticose, and the cyanobiont a single-celled member of the Chroococcales. The genus Metamelanea is based on the type species M.umbonata Henssen, newly described from the Alps, and M. melambola (Tuck.) Henssen comb, nov., found in North America. The genus Strotnatella is based on the single species, S. bermudana (Riddle) Henssen, formerly Psorotichia bermudana Riddle. The new genera are compared with species of other genera of the Lichinaceae: Gyrocollema, Lecidopyrenopsis and Porocyphus; some micrographs of Lecidopyrenopsis corticola Vainio. are also included. The new combination Porocyphus ocellatus(Th. Fr.) Henssen is made; Pyrenopsis triptococcus Nyl. is selected as lectotype of Pyrenopsis subgen. Cladopsis Nyl. (syn. Cladopsis (Nyl) Hue).

Three lichen species, Hypogymnia physodes, Bryoria capillaris and Peltigera canina were fumigated with 215 μig m−3 of SO2 (6 h per day, 5 days per week) in exposure chambers under three different moisture conditions. The treatments were (1) low humidity (40–50° r.h. continuously), (2) high humidity (80–90° r.h. continuously) and (3) high humidity + water (80–90° r.h. + daily moistening). The value of light microscopy, fluorescence microscopy and electron microscopy in assessing the SO, injury in the lichens was compared. The three lichen species studied were all damaged by this level of SO, fumigation, and injury increased with increased duration of exposure. Electron microscopy was the most sensitive method of revealing cellular injuries after 5 days of exposure in all the species studied. Fluorescence microscopy revealed changes in the colour and intensity of fluorescence after 10 days of exposure in the two epiphytic species, but no clear changes in the cyanobacterial cells of P. canina could be detected by this method. Light microscopy revealed plasmolysis of the algal cells in the two epiphytic species after 10–15 days of fumigation. All the species studied were clearly more sensitive to SO2 when cultured in air of high humidity, although slight cellular injuries also occurred in the dry air treatment (40–50° r.h.). Additional daily moistening tended to protect against injury in the lichens cultured at high humidity. In the present continuous flow fumigation chamber P. canina proved to be sensitive to SO2 in regard to ultrastructural injuries that could be observed in both the cyanobacterial and fungal cells.

Xanthoria elegans has a broad ecological amplitude, world-wide distribution and includes morphological variants which differ markedly with respect to colour, form and frequency of apothecia. Distinctive thallus forms are associated with different habitats. Samples from two contrasting habitats were studied on Ellesmere Island in the Canadian High Arctic. Carotenoids, polyphenolic products and isoenzymes were examined to establish whether two thallus types were biochemically distinct. Pigments were comparable in both morphological variants, as were approximately half of the most frequently occurring enzyme forms. Enzymatic similarity between the two resembled that between conspecific populations of other lichens. On the basis of the chemical attributes investigated, the thallus forms did not warrant recognition as fundamentally distinct entities, but were merely variants of an ecologically versatile and extremely plastic species.

Evernia prunastri thalli were homogenized and separated into algaland fungal-rich fractions. The former was shown to contain most β-l,4-glucanase (cellulase) activity. The significance of this localization in field material is discussed.