REFRACTOHILUM SPECIES WITH PLURISEPTATE C ONIDIA IN EUROPE AND CANADA

A comparative study of Refractohilum specimens with pluriseptate conid ia from Canada and western Europe shows that they belong to three spec ies: R. achromaticum, known until now only from Canada, Refractohilum intermedium Roux et Etayo sp.nov., known from subhumid parts of southe rn Europe (Mediterranean areas of France and Spain), and Refractohilum pluriseptatum Etayo et Roux sp.nov., known from western Europe and th e most humid parts of southern Europe. These three species, which grow on the thallus of corticolous and often sterile crustose lichens with Trentepohlia, differ from each other by dimensions and septation of c onidia and conidiophores, distribution, and ecology.