perithecium formation biological_process hjd 2018-09-19T19:12:53Z GO:0106154 The process of producing flask-shaped fruiting bodies, called perithecia. In the ascomycetous fungi such as Neurospora crassa and Sordaria macrospora, these perithecia are formed in the sexual phase and they discharge ascospores through the ostiolum at the tip of the perithecial neck. perithecium development