SUMMARYCellulolytic enzymes are produced byPoronia oedipusgrown on soluble and insoluble forms of cellulose. Cellulase production is negligible when the organism is grown in the presence of glucose. Optimal cellulolytic activity occurs at 50–55 C. Hydrolysis of filter paper is greatest atpH 4.2; but with carboxymethylcellulose as a substrate, optimal cellulase activity occurs atpH 4.4 to 5.0. Total accumulation of reducing sugar in the cellulase assay with filter paper as a substrate does not rise above 1% of the substrate concentration; with CMC as a substrate, approximately 5% conversion is reported.