cytological studies revealed irregularities in the nuclear life cycle of inonotus tomentosus. the mycelia was multinucleate and the nuclei were found in groups of two to six. by the time the nuclei reached the subhymenium most of the cells were binucleate. chlamydospores were multinucleate and most freshly shed basidiospores were uninucleate. the orientation of meiotic division in basidia was oblique. spindle pole bodies (spbs) were observed but microtubules were absent. postmeiotic mitosis occurred sometimes in basidia and sometimes in basidiospores. binucleate spores were occasionally observed. the dna specific dye, 4'-6-diamidino'-2-phenylindole (dapi), was used in this study. in some hyphal cells, germ tubes, and chlamydospores, dapi-positive particles (dpps) were observed. the dpps showed mostly a yellow fluorescent color. similar observations of nuclear-like material were made with associated bacteria. the dna material may be viruses or plasmids. ultrastructural studies revealed some possible bacterial-like structures and mycoplasma-like organisms in hyphae and chlamydospores. the nature and function of dpps were discussed.