Sterilized dust (40-60 mesh) of <i>D. strictus</i> was incubated with <i>Polyporus palustris, P. rubidus</i> (both brown-rot fungi), * 2Coriolus hirsutus*1 or <i>Daedalea flavida</i> (white-rot fungi) for 12 weeks at 27°C. Tests of weight loss, 1% sodium hydroxide solubility and Klason lignin showed that brown-rot fungi selectively attack cellulose while white-rot fungi attack both cellulose and lignin. <i>P. palustris</i> caused the greatest weight loss (25.2%) and <i>P. rubidus* 1 the smallest (4.1%). <i>D. flavida</i> and <i>C. hirsutus</i> caused 24.7 and 23.2% weight loss, respectively. -- AATA