Evidence from cultured and soil-borne mycelium clearly indicates that the widespread mycorrhizal symbiont (or symbionts) known as the E-strain is an ascomycete anamorph. The evidence includes regular septation, the presence of Woronin bodies and injury- and age-induced septal plugs, sensitivity to benomyl, hyphal fusions, mode of hyphal repair, and morphology of the mycorrhizae. Isolates varied in the presence or absence of chlamydospores, pigmentation, growth rates, amount of aerial mycelium, and amount of hyphal ornamentation. It is uncertain whether one or more taxa is currently included in the E-strain concept.