Aerial crystalline filaments emerged from dense type of mycelia on some monokaryotic transformants of Pleurotus florida, P. ostreatus and P. sajorcaju. Cytstals were not dissolved in water but soluble in ethanol or at the temperature of higher than $80^{circ}C$. Crystals were detected in the mycelia grown on the mushroom minimal medium as well as the mushroom complete medium. They were produced on both liquid media and agar plate. Although the mycelia incubated at $15-20^{circ}C$, produced crystals, the mycelia incubated at $30-35^{circ}C$ did not. Furthermore, crystal forming mycelia were obtained from monokaryotic basidiospore of P. ostreatus and P. sajor-caju by mutations (UV irradiation).