ABSTRACTFour species in the tribe Balansiae (Clavicipitaceae) infecting grasses and sedges were studied to determine their growth habit as endophytes or epiphytes. The genusMyriogenosporapreviously has been reported to be epiphytic but other members of the tribe have been presumed to grow endophytically in their hosts. Cultural and histological studies indicate that the speciesAtkinsonella hypoxylonandBalansia cyperioccur as epiphytes around meristems, young leaves, and inflorescences of their hosts. In contrast,B. epichloëandB. henningsianagrow endophytically within host tissues. Non-clavicipitaceous endophytic fungi were isolated from most host plants examined. The possible origins of endophytic and epiphytic growth habits and their biological consequences are considered.