Haplonts of the fungusTremella mesentericagrew in synthetic media containing any of the following nitrogen sources (in order of decreasing growth rate): glutamine, aspartate, leucine, glutamate, alanine, ammonium sulfate, serine, soytone, casein hydrolysate, phenylalanine, and asparagine. Cultures with potassium nitrate, cysteine, glycine, histidine, lysine, or proline as sole N source did not grow. Thiamine was the only vitamin required. Asparagine slowed the growth of some strains and also caused the cells to become large and spherical.