sentences:  The symbiosis appears to have existed already during the early grass evolution that has spawned today's pooid grasses.This is suggested by phylogenetic studies indicating a preponderance of codivergence of "Epichloë" species with the grass hosts they inhabit.Growth of the fungal symbiont is very tightly regulated within its grass host, indicated by a largely unbranched mycelial morphology and remarkable synchrony of grass leaf and hyphal extension of the fungus; the latter seems to occur via a mechanism that involves stretch-induced or "intercalary" elongation of the endophyte's hyphae, a process so far not found in any other fungal species, indicating specialized adaptation of the fungus to the dynamic growth environment inside its host.