The chromosome number ofRosellinia mammiformisisn = 6. Ascospores are uninucleate when formed, becoming binucleate by mitosis. One of the nuclei degenerates; maturing ascospores are uninucleate. Ascospores show apical appendages that are proliferations of the outermost wall or perispore. The chromosome number ofRosellinia aquilais tentativelyn = 6. Ascospores are at first uninucleate, becoming binucleate by a mitosis. One of the nuclei degenerates and is often cut off in an appendage. Maturing ascospores are uninucleate and show two types of appendages. Secondary appendages are formed from the perispore. Primary appendages are cut off from the spore body by a septum and are surrounded by the secondary appendage. In addition, a double primary appendage, part of which probably functions to trap a degenerating nucleus, is described. The significance of these results is discussed.