Studies on the development of perithecium of Ceratocystis stenoceras

The development of the perithecium of Ceratocystis stenoceras was observed by a light microscope and by a scanning electron microscope.The fungus has developed dark brown perithecia on wheat agar medium in three days of incubation. Perithecial primordia appeared as tightly knotted coils. At the center of it an oval ascogonium was observed. The ascogonium was developed from a lateral wall of a hypha, and the hyphae covering the ascogonium branched at the basal part where the ascogonium was attached. These hyphae branched repeatedly in the developmental growth to cover the ascogonium, and it was finally covered tightly. The plasmogamy of this fungus is much probably performed by the gametangial contact. As the stage proceeded, the ascogonium elongated, the terminal and the basal portions of it swelled and cleavage of the ascogonium resulted. Each of the cleaved ascogonia germinated continuously and stretched out the ascogenous hyphae. About that time the cells consisting of perithecia were vacuolated from the center and successively dissolved, so that a space was formed in the center of the body. Ascogenous hyphae continued to develop downwards, and their end were fixed to the inner wall of the body.The upper portion of the hyphae converged to the center of the body and the ascogenous hyphae became the supporting tissue for ascus formation.Hook formation was observed prior to the ascus formation. After completion of karyogamy by hook formation, the fissure appeared on the ascus and the end portion was released. The released portion included eight ascospores. The ascus had a smooth surface and no special structure was seen on the top. As the asci were matured, they evanesced by themselves and concurrently ascospores came out. Finally the body was massively filled with ascospores.