CRYOSTAT MICROTOME SECTIONS OF BIRCH WOOD DEGRADED BY WHITE ROT FUNGI WERE EXAMINED BY LIGHT MICROSCOPY AFTER TREATMENT WITH TWO STAINS: astra-blue, which stains cellulose blue only in the absence of lignin, and safranin, which stains lignin regardless of whether cellulose is present. The method provided a simple and reliable screening procedure that distinguishes between fungi that cause decay by selectively removing lignin and those that degrade both cellulose and lignin simultaneously. Moreover, morphological characteristics specific to selective delignification were revealed.