Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights Reserved.): Calcofluor staining of the Ustilago maydis sep3 deletion mutant showing cells with aberrant morphology and septation. The &dgr;sep3 haploid cells often possess a single septum located in the center of the cell, and this results in a distinctive lemon drop shape. Occasionally, the mutant cells can also possess multiple septa and display an uneven distribution, or an increased accumulation, of chitin. (See related article on p. 2044.)