ABSTRACTThe sedge parasiteKriegeria eriophoriwas examined with light and electron microscopy to elucidate its basidial development and life history. Hyphae occur in xylem vessels in the leaf. Thin-walled, saccate probasidia form within the leaf and are the site of karyogamy and meiosis I through late prophase. They develop filaments that break through the probasidial wall and grow through the stomata to the underside of the leaf and there form metabasidia. Meiosis is completed in the metabasidia, which produce both ballistospores and yeast cells. Spores may reproduce asexually in the field and in culture by budding as a yeast with candelabra-like morphology, and this anamorph is named here asZymoxenogloea eriophori.Basidial development is compared to that of other heterobasidiomycetes and its phylogenetic significance is discussed.