<u>Endothia parasitica</u> (Murr.) P. J. & H. E. Anderson (syn: <u>Cryphonectria parasitica</u>(Murr.) Barr), the causal agent of chestnut blight, was able to grow in total aqueous and tannin extracts from blight-susceptible American chestnut as well as in blight-resistant Chinese chestnut bark extracts, from winter and summer bark. Differences in the amount of conidial germination and growth in extracts of the two species were small. The, <u>E. parasitica</u> tannase was more abundant intracellularly than extracellularly. Total tannase activities from cultures in American chestnut aqueous and tannin extracts were greater than in the Chinese chestnut extracts, for both winter and summer bark. The tannase was isolated from the mycelium of E. parasitica and purified 142-fold with a 10% yield by anion exchange chromatography and gel filtration. The estimated molecular weight was 240 kD and the molecule may be a tetramer composed of four subunits with a molecular weight of 58 kD. The pH optimum of the purified tannase was 5.5 and the temperature optimum for activity was 30 C. The enzyme was separated into six bands in the pH range of 4.6 to 5.1 which may represent isoenzymes or post-translational modifications. / Ph. D.