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Physical properties and chemical structure of two related polysaccharides produced fermentatively by Plectania occidentalis NRRL 3137 and by Helotium sp. NRRL 3129 were studied. Both polymers were readily recovered as amorphous gels by precipitation from culture liquors with two parts of ethyl alcohol or methanol. Dried polymeric material was redissolved in water with agitation to give uniform aqueous solutions up to about 1.5% by weight. The polymers were similar in physical properties but possessed different chemical structures. The viscosity of aqueous solutions of each polymer varied from about 50 centipoises at 0.1% to approximately 2,200 centipoises at 1.4% concentrations by weight. Highly viscous solutions at concentrations of 1% or greater behaved like thixotropic gels. Mono-, di-, and trivalent salts, except borate, did not affect viscosity of either polymer. The viscosities were slightly increased by the addition of borate. Autoclaving did not alter the physical properties of neutral polymer solutions. The polymers were stable in acid or alkaline solutions at moderate temperatures but degraded under extremes of pH at 70 C or above. Each polymer had a specific rotation of +20 degrees in aqueous dimethylformamide (1:1). The results of acid hydrolysis and periodate oxidation, in conjunction with paper and gas chromatography, indicate that both polymers are branched glucans containing appreciable amounts of beta-1,3 linkages.