Four types of ascomycete mycorrhizas were found on seedlings of Abies alba grown in pot cultures on mineral soil. One type was formed by Cenococcum graniforme Ferd. & Winge; the fungal partners of the other three types could not be identified. The macroscopic and microscopic characteristics are described. One mycorrhiza appeared to be identical with Type 15 of Haug & Oberwinkler, found in natural spruce stands. Senescent stages of this type are also described. Ultrastructural investigations showed that the dolipore seemed to be the main distinguishing feature between ascomycete and basidiomycete mycorrhizas. Differences in the matrix of the interface and the fungal wall were not stable enough to be used as a distinguishing feature between asco- and basidiomycetes. Dead fungal cells were isolated from the living tissue by plugging of septa with Woronin bodies and walling-over of the plugged septa. Subsequently these isolated dead cells could be colonized by the fungus. The predominant mycorrhization of the fir seedlings by ascomycetes in pot culture with mineral soil is discussed.