Microbotryum violaceum (anther-smut) from Silene caroliniana and S. virginica produced promycelia that frequently appeared to contain more than three cells according to the number of septations. This is in contrast to samples from S. latifolia and to previous descriptions of this species. Apparent four-celled promycelia contained three nucleate cells and one anucleate zone. Anucleate zones were usually positioned between the first and third cells of the promycelium. Their presence was negatively correlated with the occurrence of intra-promycelial conjugation. Also, unlike isolates from Silene latifolia, isolates from S. caroliniana and S. virginica produced hyphae in the absence of an inducing agent.