Abstract: Previous research on Microbotryum violaceum, the fungal pathogen that causes anther smut disease in Silene alba, has used a model of dispersal in which the diploid teliospore  stage represented the only mode of disease transmission.  However, recent findings suggested that the haploid sporidia of M. violaceum may also be transported between flowers within S. alba populations and between other species of plants.  This has raised many questions about the ability of M. violaceum sporidia to form free-living populations and possibly serve as another route of infection.  Experimental arrays were used to examine sporidial transmission between S. alba individuals,  and a model was formulated to calculate the ability of  M. violaceum to form self-sustaining populations in S. alba individuals.  The results obtained from these experiments indicated that sporidia are transferred between plants.  The model showed that male flowers are able to sustain sporidial populations, but females are not.  However, while sporidial populations may persist in individual flowers, it is unlikely that they can persist in populations of S. alba.   The haploid sporidia therefore do not appear to represent another major route of infection.