The lichen flora of the Nordic countries, containing more than 2000 species, is regarded as one of the best known in the world. Lichenological research of the region has been continuous since the time of Erik Acharius (1757-1819), the "Father of Lichenology", but it is a sad fact that there is no modem total treatment of the region's impressive lichen flora, the last attempt being that of Th. M. Fries in the 1870's. His major work, Lichenograprua Scandinavica, unfortunately remained unfinished.
A number of lichen specialists have united forces to produce this much needed Nordic Lichen Flora. The present sixth volume, dedicated to some important genera of the family Verrucariaceae and edited by Roland Moberg, Sanja and Leif Tibell, includes treatments of 64 species representing the genera Atla, Catapyrenium, Clavascidium, Dermatocarpon, Henrica, Heteroplacidium, Involucropyrenium, Placidiopsis, Placidium, Polyblastia and Sporodictyon.
The study is based on material in the major Nordic herbaria in addition to extensive field work in all the Nordic countries. DNA analyses of most species have also been conducted. The thorough work has resulted in many new findings, but also revealed new, often still unsolved problems, which are pointed out in the discussions after each species. The total distribution of each species is also carefully indicated, based on the authors knowledge. Recent molecular investigations have supported the monophyly of Verrucariaceae, but also revealed many problems in the genera as traditionally circumscribed during the pre-molecular era. This volume is the beginning of a modem treatment of the family.