119 investigated Quercus trunks and 67 species of lichens, 23 bryophytes and 3 non-lichenized fungi are arranged by means of the Minimum Spanning Tree analysis, resulting in four Lobarion communities and one Parmelion community. Lobarion is restricted to bark with pH > 5.0 in old forests. pH and Ca-content in the bark are strongly correlated; Ca seems to originate from Ca-uptake through the roots of the phorophyte. Within a single site the soil also seems to be responsible for the variation in the Mg-content of the bark, being correlated with Ca. The dominating source of the regionalvariationinMg, however, seems to be marine aerosols. Parmelion caperatae occurs on acid bark of young trees. The bark is, however, rich in Mg. Soluble tannins in the bark decrease with increasing age of the phorophyte, but are probably of minor significance for the epiphytic vegetation.

Where two crustose lichen thalli meet at a ‘ truce ’ boundary theshape of the boundary can be used to evaluate models of how lichen growth rates change with thallus size. The application of this method to studies of intra- and interspecific competition are discussed.

Synthetic thalli of Usnea strigosa produced the same fibril morphology and secondary compounds as natural thalli. The outer cortex of synthetic lichens was covered with crystals of usnic acid and compounds related to norstictic acids. The common presence on the fibrils of lichen acids suggests that these compounds have a functional role in the symbiosis. During alcohol dehydration, crystals of usnic acid dissolved and left impressions in the mucilage around the symbionts. The impressions were valuable indicators of the position of crystals in the lichen thallus. Crystal impressions of usnic acid were common on the cortical hyphae and were seen also on the surface of algal cells. The crystal impressions were larger in the synthetic lichen than in natural thalli. Impressions of norstictic acid and related compounds were not seen.

The lichen flora was sampled at each of the five sites on a near-vertical gneiss rock face. The sites were ranked according to the degree ofweathering of the rock surface and were taken to represent different stages in a succession. The succession shows an increase in species richness and diversity over time, although the proportion of the rock face unoccupied by lichens increases at the oldest site. The succession will be driven by allogenic processes, physical weathering of the rock, facilitation, especially the effects of lichens on surface erosion, and by inhibition, through competition for space. At the oldest site mortality of lichen thalli becomes important, continually opening up new areas for recolonization and maintaining community diversity. The succession may be described by four phases: (1) colonization, (2) growth,(3) competition and (4) senescence.

The Southern Hemisphere genus Psoromidium Stirton (Lecanorales, Pannariaceae) is closely related to certain elements within the heterogeneous genus Psoroma Michx, but is distinguished by the absence of a photobiontin the apothecial margin. In Psoromidium, as in Psoroma, the main photobiont is green and is present in a layer below the upper cortex of the squamules; Nostoc occurs in scattered, well-defined cephalodia. Two species are known: P. aleuroides, with an Australasian distribution, and P. versicolor, anaustral species from Tasmania, Fuegia and the subantarctic Auckland Islands group of New Zealand. Anatomy, morphology, distribution, habitat ecology and taxonomy of the two species are discussed. Psoromaria Nyl. is a synonym of Psoromidium.

A third fascicle of a lichen exsiccata containing species of Caliciales has been issued; 24 species from New Zealand arc included. Remarks on taxonomy, chemistry, ecology and distribution are given here. Detailed descriptions of Calicium cryptocroceum Tibell, Coniocybe amabilis Tibell and Sphaerophorus notatus Tibellare provided. In addition to the three species described as new in the schedae, Calicium glaucellum Ach., Chaenotheca brunneola (Ach.) Müll. Arg., C. carthusiae (Harm.) Lettau, C. ferruginea (Turnerex Sm.) Migula, C. hispidula (Ach.) Zahlbr., C. stemonea (Ach.) Mull. Arg., Chaenothecopsis debilis (Turner & Borrer) Tibell, C. lignicola (Nádv.) A. Schmidt, C. pusilla (Flörke) A. Schmidt, C. savonica (Räs.) Tibell, C. viridireagens (Nádv.) A. Schmidt, Microcalicium arenarium (Hampe ex Massal.) Tibell, and M. disseminatum (Ach.) Vain, are reported new to the Southern Hemisphere; Chaenotheca trichialis (Ach.) Th. Fr., Coniocybe gracillima Vainioand C. sanguinea Tibell new to Australasia and Microcalicium conversum Tibell and Mycocalicium subtile (Pers.) Szat. new to New Zealand.

Schismalomma ceylanicum sp. nov. is described from Sri Lanka, and an account is given of two species from California previously assigned to Dirina: S. calijornicum(Tuck.) Zahlbr. and S. rediunta (Hasse) comb. nov.