Current Review: Viroids: From Thermodynamics to Cellular Structure and Function. Detlev Riesner. Heinrich-Heine-Universität Düsseldorf, Institut für Physikalische Biologie, 4000 Düsseldorf, Federal Republic of Germany. . MPMI 4:122-131. Accepted 10 December 1990. Copyright 1991 The American Phytopathological Society.