1.The karyological phenomena in the life-cycle ofFomes lividusKalchbr., a resupinate member of the family Polyporaceae has been studied in detail.2.The young basidium is distinctly binucleate. This dikaryotic condition comes to an end with their fusion to form a synkaryon. The synkaryon first undergoes an interphasic enlargement followed by the appearance of chromatic materials as reticulate structure. Subsequently, from the reticulum typical chromosomes (2n= 6) are formed. A haploid chromosome set constituting a genome (n= 3) forms a daughter nucleus at each pole. The orientation of the spindle of the first division of meiosis (heterotypic) is more or less transverse while in the second division (homotypic) it shows irregularities. A third nuclear division occurs forming the eight nucleate condition of the basidium. Four of these eight nuclei migrate into four developing basidiospores while the other four degenerate in the collapsing basidium. The nucleus within the basidiospore often divides before the liberation from the sterigma.3.The mature uni- or binucleate basidiospore on germination produces one to three germ-tubes. The germ-tubes are either quite narrow or of the same width as that of the spores. As the germ-tubes enlongate, their nuclei repeatedly divide, formation of septa follows and eventually a septate primary mycelium of uninucleate cells without clamp-connexion is formed.4.The secondary mycelium, with characteristic clamp-connexion and binucleate cells, is formed only when two compatible primary mycelia unite.