Ultrastructureof the ascus and the ascospores

The ultrastructure of the ascusand the ascospores inPseudascozonus is described. The top of the ascus opens by a small rather roughly delimited operculum. A circular furrow in the inner ascal wall causesa weakened zone. The development of the ascospore wall shows a simple homogeneous epispore and disappearance of all secondary wall material. In the epiplasm of the ascus a unique type of envelope, surrounding all eight ascospores, is described. Relationship with Asco-zonusand Theleboli with 8-spored asci is suggested. The aim of this study is to reveal the fine structure of the ascus and the ascospores with the help of electron microscopy. MATERIALS AND METHODS The material of Pseudascozonus racemosporus was isolated from deer dung collected at the type locality of the species, at the 'Tourbière de Frasne', Frasne, dép. Doubs, France, 20 III 1985 ( van Brummelen 7398)