Abstract
The ontogeny of two species of Thecotheus, T. pelletieri and T. cinereus, was studied to aid in the clarification of the taxonomy of the genus. Bulbous cells that terminate many of the vegetative hyphae and which eventually form the ectal excipulum in both species and a sympodial conidial state in T. pelletieri indicate that the genus Thecotheus shares characteristics with three families, the Ascobolaceae, the Pezizaceae, and the Pyronemataceae. Cultural studies indicate that T. pelletieri and T. cinereus are heterothallic. The imperfect state of T. pelletieri is morphologically similar to Rhinocladiella.