Studia Forestaeia Suecica

ODC-844.2 The ability o f the soft rot fungus Humicola alopallonella Meyers & Moore to form cavities in various cellulose fibres has been studied. The following fibre materials were tested: wood of aspen, beech, birch, pine and spruce, three sulphate pulps with different lignin content, spruce holocellulose, Avicel, Sigmacell T38, flax, jute, ramie, sisal, cotton, kapok, seed hairs o f Salix pentandra L, and two viscose rayon fibres. In addition the degradation o f cellophane was studied. Typical soft rot cavities were formed in all the natural fibres except for spruce holo cellulose tracheids. The cavity formation in fibres like Avicel, Sig-macell T38 and cotton which contain no or possibly minute amounts o f lignin and hernicelluloses, shows that these substances are not needed for cavity formation per se. The shape o f the cavities is rather similar in all the natural fibres, indicating that the explanation o f the form o f the cavities must be sought in the crystalline structure o f the cellulose. Various aspects o f the process o f cavity formation are discussed in the light o f the new findings.