A crude cellulolytic enzyme prepq.ration derived from Trichoderma viride was capable of solubilizing native crystalline forms of cellulose. Enzyme activity ("hydrocellulase") was determined by measuring the decrease in turbidity of the assay reaction mixture which contained a suspended hydrocellulose substrate.

Preliminary studies of "hydrocellulase" showed that under assay conditions maximum activity was obtained at pH 4.7 to 4.8 and at 40° for 3 hours. The activity was relatively stable for a three hour period between pH 4.0 and 7.0 and at temperatures up to 40°. Cellobiose was several times more inhibitory than glucose. Methylcellulose was very inhibitory. Sulfhydryl compounds stimulated activity of the crude preparation. EDTA was without effect.