XVI International Botanical Congess

Lichens of the Physciaceae occur on deciduous trees and form a significant part of the vegetation on trunks and small twigs. Interactions with species of the Teloschistaceae may occur and observations have shown that these may be of special importance in the first colonization of twigs. The growth of thalli on a new substrate requires suitable reproductive mechanisms and fertile species have to produce a sufficient number of germinating ascospores. Experiments have shown that germination of spores in some species of Physciaceae is influenced by the presence of certain nutrients. The isolated mycobiont differs from other isolated lichen fungi by its growth-pattern and by the amount of biomass produced over longer periods of cultivation. It can be postulated that these characteristics of the mycobiont may also be of importance in the lichen symbiosis.