Fungi inhabiting healthy stems and branches of American beech and aspen were induced to develop within the wood by drying sections of these organs. The two tree species were similar in that tile water content of the wood strongly determined fungal development, with a high water content preventing fungal growth for at least 25 weeks, fast drying resulting in poor development and slow drying inducing very fast growth of fungi within the wood. Fungal assemblages thus obtained were strongly dominated by ascomycetes and coelomycetes.
Although some fungal species appeared on both tree species, assemblages of fungi obtained from each tree species were clearly different, even though samples of each were obtained from the same site and all experimental conditions were identical for both.
All the characteristics mentioned above strongly resemble those documented for endophytes on smaller aerial tree organs such as leaves, petioles and twigs, and for this reason the fungi obtained here were termed‘xylotropic endophytes'.
Among the dominant species found on aspen, three species with presumed pathogenic abilities were isolated. These were Cryptosphaeria populina, Cytospora chrysosperma and Hypoxylon mammatum. Hypoxylon fragifarme was the most frequently and abundantly isolated species obtained from beech.