Blastomyces dermatitidis: production of the sexual stage.

Growth of five combinations of strains of Blastomyces dermatitidis in paired cultures on yeast-extract agar, plus bone meal, yielded the perfect stage for the first time. These cleistothecia, apparently of a new genus, produced eight spored asci. Monoascospore cultures developed hyphae and conidia typical of B. dermatitidis. Mice were successfully infected with inocula from a monoascospore culture.