Dr. R.A. Maas Geesteranus 80 years

This special issue of Persoonia is dedicated to Dr. R. A. Maas Geesteranus who celebrated his 80th birthday on January the 20th 1991 in good health and spirits. Dr. Maas Geesteranus retired in 1976. On this occasion a biographical note and a list of his publications were published (Persoonia 8: 335-343. 1976). What only could be hoped then has fortunately come true: he intensively continued his excellent research in the taxonomy of macromycetes. In the last fifteen years an uninterrupted stream of more than 50 papers were published.