The crystalline polymorphic form of cellulose (cellulose Ia-rich) of the green alga,Cladophora, was converted into cellulose III I and Ib by super-critical ammonium and hydrothermal treatments, respectively, and the hydrolytic rate and the adsorption of Trichoderma viridecellobiohydro-lase I (Cel7A) on these products were evaluated by a novel analysis based on the surface density of the enzyme.