A tribute to Professor Tor Tønsberg.

This article is a tribute to Professor Tor Tønsberg on his 75th birthday. It includes 20 papers related to his scientific interests in lichenology, specifically the taxonomy, chemistry, floristics, and phytogeography of lichens and lichenicolous fungi. Throughout his career, Professor Tønsberg has made significant contributions to the knowledge of lichens in Europe and North America, introducing over one hundred new species and genera. The article expresses gratitude to the authors for their contributions and celebrates Professor Tønsberg's impressive achievements in the field. [Extracted from the article]