SUMMARYThe cellulase system ofPoronia punctatahas properties similar to that of other fungi.Poronia punctatacellulase assays on carboxymethyl cellulose (CMC) demonstrated major and minor peaks of activity atpH 4.8 and 5.6 respectively. A side peak of activity occurred atpH 4.4 but its exact nature or relationship to CMC hydrolysis is unclear.Poronia punctatacellulase assays on microcrystalline cellulose (MCC) and filter paper demonstrated reversedpH values for major and minor peaks of hydrolysis compared to the CMC experiments; the major peak of activity occurred atpH 5.5 with the minor peak atpH 4.6. These results suggest the presence of a dual enzyme system inP. punctata.Optimal temperature activities forP. punctatacellulase were demonstrated to be 55 C with CMC as substrate and 45 C with filter paper and MCC as substrates. Assays using filter paper as a substrate do not rise above 1% total conversion to reducing sugar; with MCC as substrate, approximately 2.7% is converted, and with CMC as substrate a yield of 4.7% is obtained.