The process is described of teliospore germination in Tilletia opaca and T. sumatii leading to the production of basidiospores on basidia, and later the development of ballistospores and blastospores on agar. In both species the basidium shows some evidence of being a condensed dichotomously branched structure. The situation in these two smuts is discussed in relation to that in several other species of Tilletia, and some consideration is given to the origin of the basidium and evolutionary trends within the genus.