Abstract
The morphology of the extracellular mucilaginous material (ECM) produced by Coniophora puteana and Coriolus versicolor during
colonization of Scots pine and beech was studied using SEM. Wood specimens were examined in the frozen hydrated (FH) condition
using low-temperature SEM, and in the freeze-dried (FD) and critical point dried (CPD) state, using conventional SEM. All techniques
produced artifacts but the ECM was best preserved when examined in the FH state. Very little difference was observed between FH
and FD preparations, but critical point drying damaged the ECM extensively. Copious amounts of ECM were produced by both
fungi. It was found to line much of the lumen surface, establishing contact between the mycelium and the wood substratum. Most
aerial hyphae were coated with ECM, appearing glued together in a bundle-like fashion. The ECM thickness varied within the same
wood cell and from one cell to another. A peculiar granular pattern, in which the ECM was definitely involved, was seen on
occasion to encircle the infecting hyphae where they contacted the wood surface. Other morphological patterns of ECM distribution
were also observed. Calcium oxalate crystals of varying shapes and sizes were often seen associated with the mycelia and mucilage
of the two fungi in beech but not in Scots pine. The probable roles played by the ECM in wood decay mechanisms are discussed.