A key is provided to the 81 saxicolous species and infraspecific taxa of Porina Ach. (Trichotheliaceae). It includes diagnostic characters, broad distributional and some habitat information, as well as references to more complete descriptions.

Four new pyrenocarpous lichens are described from Rarotonga, Cook Islands, South Pacific Ocean: Porina deminuta (Trichotheliaceae), Pyrenula ochraceoflava var. pacifica (Pyrenulaceae), Strigula decipiens var. divisa (Strigulaceae) and Verrucaria fortuita (Verrucariaceae). The new combinations Porina eminentior (Nyl.) P. M. McCarthy and P. exocha (Nyl.) P. M. McCarthy are made for Thelenella eminentior Nyl. (Clathroporina eminentior (Nyl.) Müll. Arg.) and Verrucaria exocha Nyl. (Clathroporina exocha (Nyl.) Müll. Arg.), respectively. Brief descriptions and additional notes are provided for 26 other taxa. The phytogeographical affinities and possible origins of the pyrenocarpous lichens of Rarotonga and Lord Howe Island are discussed.

Ten parmelioid taxa in five genera were identified from Rarotonga, Cook Islands, South Pacific Ocean. These comprise: three species of Bulbothrix, one species of Canoparmelia, four species of Parmotrema, one species of Rimelia and one species of Xanthoparmelia. Canoparmelia rarotongensis Louwhoff & Elix is described as new, being distinguished from other species of this genus by its unique secondary chemistry (lecanoric acid) and conspicuous, inflated isidia. The majority of parmelioid lichens on Rarotonga have cosmopolitan and pantropical distributions. Bulboihrix is reported for the first time from the Polynesian region.

The new species Santessoniella rosettiformis Henssen is described from a temperate Nothofagus forest in southern Chile and compared with the superficially similar S. pulchella P. M. Jørg. In both species, the thallus is corticate on all surfaces, the characteristic feature separating Santessoniella from Parmeliella. In the blue iodine reaction of the hymenium and the presence of smooth spores, S. rosettiformis corresponds to the closely related S. chilensis (Hue) Henssen whereas S. pulchella with warty spores and reddish brown hymenium in iodine is related to S. polychidioides (Zahlbr.) Henssen, the type species of the genus. A key to the species of Santessoniella is provided; the delimitation of the genus is discussed.

Fifteen species of Usnea are recorded from Iberian cork-oak forests: U. ceratina, U. comma, U. dasaea, U. esperantiana, U. flammea, U. fulvoreagens, U. glabrata, U. hirta, U. mutabilis, U. rubicunda, U. subcornuta, U. subfloridana U. subscabrosa, U. substerilis and U. wasmuthii. A key for these species is provided. Details of morphology, chemistry, distribution, ecology and taxonomy are discussed. Usnea dasaea is reported as new to the Iberian Peninsula. New chemotypes of U. fulvoreagens (with squamatic acid) and U. wasmuthii (with psoromic acid) have been identified. Distribution maps of U. dasaeaand U. subcornuta in Europe are presented. A new combination, Usnea subfloridana subsp. praetervisa (Asahina) P. Clerc, is proposed.