The distribution patterns of lichens belonging to the family Peltulaceae and procaryotic algae (cyanobacteria) were studied in a rock pool on a sandstone koppie (‘Inselberg’). situated in the mopane savanna of the northern Transvaal. The co-dominant lichen species along the wall of the pool were: Peltula clavata (Krempelh.) Wetmore, P. euploca (Ach.) Poelt ex Pisut, P. obscurans (Nyl.) Gyelnik, and P. placodizans (Zahlbr.) Wetmore. The cyanobacteria Gloeocapsa sanguinea (Ag.) Kütz. emend. Jaag, Plectonema tomasinianum Gom. ex Gom., Rivularia sp., Scytonema sp. and Tolypothrix sp. grew epilithically between the lichen thalli. Unicellular species of the genus Chroococcidiopsis Geitler or Myxosarcina Printz occurred cryptoendolithically. The distribution patterns of several lichen species are presented and statistical tests reveal distinct correlations of the habitats of some species with light levels and water supply; e.g. the olive-green P. placodizans preferred the fully exposed situation near and along the rim of the rock pool; the black species P. clavata was restricted to areas next to the water level.

Axenic cultures of lichen mycobionts and photobionts were assayed for biological ice nucleation activity (INA), a characteristic which has recently been discovered in some species of lichens collected from nature. Of 14 species of mycobionts, five showed nuclei active at −5°C or warmer, while none of the 13 photobionts tested had INA at that temperature. It appears that biological ice nuclei in lichens are produced primarily by the mycobiont. Rhizoplaca chrysoleuca had the greatest INA. Other lichen fungi showing warm temperature INA were Cladonia boryi, Cladonia rangiferina, Lecanora dispersa, and Pertusaria flavicans. Lichen INA may be involved in moisture uptake and/or frost protection.

The terricolous lichen flora on the Dungeness shingle, in south-east England, includes an abundance of members of the Cladonia chlorophaea complex. From a detailed examination of morphological and chemical attributes, the ‘species’ present are identified as Cladonia chlorophaea s. str., C. fimbriata, C. humilis, C. merochlorophaea, C. cryptochlorophaea and C. merochlorophaea var. novochlorophaea. Cladonia fimbriata and C. chlorophaea are dominant on the younger, more seaward ridges, whilst C. merochlorophaea becomes important on the older ridges. Cladonia humilis is confined to sandy substrata.

Column and thin-layer chromatography revealed the presence of the following carotenoids in the thalli of seven lichen species from Ireland: α-carotene, β-carotene, β-cryptoxanthin, lutein, 3'-epilutein, adonixanthin, α-doradexanthin, canthaxanthin, astaxanthin, antheraxanthin, lutein epoxide, neoxanthin and violaxanthin. The total content of carotenoids ranged from 11.9 μg g−1 dry wt in Menegazzia terebrata to 21·3 μg g−1 dry wt in Usnea rubicunda.

The effects of fluoride and sulphur dioxide on the germination of ascospores of Lecanora conizaeoides, Xanthoria parietina, Physconia distorta and Peltigera canina were studied under controlled conditions. The two pollutants (H2SO3 and NaF) were dissolved in the culture medium. An improved culture technique permitted a high percentage germination (90° 0) of P. canina spores. Peltigera canina spores had the highest sensitivity to SO2 (no germination at 500 UM H2SO3). Lecanora conizaeoides spores were almost insensitive to each of the two studied pollutants (30°0 spore germination at 1000 UM H2SO3 or NaF). However, simultaneous exposure to 1000 UM H2SO3 and 1000 UM NaF resulted in no germination, indicating a synergistic effect of these products.

Four enzymes were examined electrophoretically from each of seven stands of arctic umbilicate lichens in central Ellesmere Island. The species studied included Umbilicaria virginis Schaerer, which was prolifically apotheciate, and U. decussata (Vill.) Zahlbr. and U. hyperborea (Ach.) Hoffm., which were both sterile. Electrophoretic banding patterns were converted to presence/absence data reflecting the occurrence of electromorphs in each thallus, and enzyme polymorphism was assessed using three statistical methods, one based on frequency of individual enzyme forms, another on the number of banding patterns, and a third on the proportional representation of different band patterns within each collection site. Greater enzyme variability occurred in stands of apotheciate species than in stands of species which were asexual in the study area, suggesting that regular sexual reproduction contributes to greater diversity.