The sorediate and isidiate, corticolous, crustose lichens in Norway

128 species in 45 genera of sorediate and isidiate, crustose, corticolous lichens are recorded from Norway. Accounts of their morphology, chemistry, and substratum preferences are presented, and a discussion of their distribution in Norway is supported by maps for a number of taxa. With few exceptions, the taxa can be distinguished on thallus characters alone. Several taxa, especially those with brown or blue-pigmented soralia, have soredia with a distinct cortex. New species are: Buellia arborea Coppins & Tønsb. (from Norway and Scotland), Fuscidea arboricola Coppins & Tønsb. (from Norway, Sweden, and Scotland), F. pusilla Tønsb. (from Norway, Sweden, and Scotland), Lecanora flavoleprosa Tønsb. (from Norway and Austria), L. flavopunctata Tønsb. (from Norway and Sweden), L. norvegica Tønsb. (from Norway), Lecidea gyrophorica Tønsb. (syn. L. epizanthoidiza auct., non Nyl.), L. praetermissa Tønsb. (from Norway and Sweden), L. subcinnabarina Tønsb. (from Norway), L. vacciniicola Tønsb. (from Norway, Sweden, and Spain), Lecidella subviridis Tønsb. (from Norway and Sweden), Lepraria elobata Tønsb. (from Norway), L. jackii Tønsb. (from Norway), L. obtusatica Tønsb. (from Norway), L. umbricola Tønsb. (from Norway, England, and Scotland), Micarea coppinsii Tønsb. (from Norway and Scotland), Rinodinaflavosoralifera Tønsb. (from Norway), R. disjuncta Sheard & Tønsb. (from Norway and the pacific coast of U.S.A. and Canada), and Schaereria corticola Muhr & Tønsb. (from Norway, Sweden and Scotland). Ochrolechia androgyna s. lat. is shown to comprise at least four distinct species. New combinations are: Cliostomum leprosum (Räsänen) Holien & Tønsb., Lepraria rigidula (B. de Lesd.) Tønsb., Mycoblastus caesius (Coppins & P. James) Tønsb., Placynthiella dasaea (Stirton) Tønsb., and Ropalospora viridis (Tønsb.) Tønsb. Lecidea turgidula var. pulveracea Fr. is raised to specific level with the new name Lecidea leprarioides Tønsb. Mycoblastus sterilis Coppins & P. James is reduced to synonymy with M. fucatus Stirton. Pertusaria borealis is new to Europe. Halecania viridescens, Lecanora farinaria, Lepraria caesioalba Laundon ined., L. eburnea Laundon ined., Megalospora tuberculosa, Opegrapha multipuncta, and Scoliciosporum gallurae are new to Scandinavia. Mycoblastus caesius, Lecidella elaeochroma “f. soralifera”, L. flavosorediata, Micarea granulans (saxicolous, not treated), Opegrapha sorediifera, and Rinodina degeliana are new to Norway. In some cases, Poelt’s species pair concept can be applied to this group of lichens. Additional secondary substances, not occurring in the primary species, sometimes occur in the soralia of the secondary species. In this case, presence of the additional substance cannot be regarded as an independent taxonomic character, and the species pair concept is still useful. However, morphologically indistinguishable specimens with different chemistry may represent different secondary species. The term consoredia is introduced to denote diaspores composed of aggregated soredia.