SUMMARYCryptomycinais a systemic parasite. The fronds of an infected plant produce pycnidia and ascostromata in early summer. Archicarps and emergent trichogynes are formed in a central meristem but degenerate in late summer without functioning. Ascogenous hyphae arise in late summer from the intact or fragmented strips of the central meristem. The asci arise from either the intact or fragmented strips without the intervention of croziers. Fusion of nuclei in the ascus takes place after the fronds have died and fallen to the ground, in late summer. The asci increase in size over the winter, but the fusion nucleus remains in the resting stage. Meiosis and the formation of ascospores takes place during the warm rains of early spring.