Uni-clonal cultures of selected wood inhabiting marine Ascomycetes and Deuteromycetes developing on Manila twine in vessels containing 0.1per thousand yeast extract and sea water have shown extensive cellulolytic activity accompanied by significant loss in the tensile strength of the fiber. The residual tensile strength of the twine varied with attack by different fungal species, from 74 to 183 lb., compared with the 260 lb. tensile strength of the uninoculated twines. Because of the close similarity of cordage and wood in proximate analysis except for the lower lignin content of the former, it is believed that the notable loss of strength of cordage when used as a growth substrate for the various lignicolous sea water fungi is a positive demonstration of the destructive action of these organisms on wood fibers.