Germinating teliopspores of Tilletia caries, T. foetida, and T. controversa were stained with acetic orcein and examined with light microscopy. The general nuclear events were the same in the three species. Nuclei in teliospores stained only after a period of incubation. Teliospores contained a single interphase nucleus, which underwent meiosis and then zero to two synchronous mitotic divisions. At metaphase I – anaphase I, approximately four chromosomes were visible in each species. The nuclei migrated from the teliospore into the promycelium and then each migrated into a primary sporidium. At this stage there were usually fewer nuclei than primary sporidia. The nuclei divided almost synchronously in the primary sporidia, after which one of the daughter nuclei in each primary sporidium migrated to the tip of the promycelium and then into any remaining anucleate primary sporidia. Supernumerary nuclei remained in the promycelium or in the primary sporidia and eventually lysed. Mature primary sporidia usually contained one interphase nucleus. When T. caries and T. foetida were germinated at 5 as compared with 15 °C, the nuclei in most teliospores underwent one less synchronous division and the number of primary sporidia was reduced.