A histo-cytological study of Norway spruce [Picea abies (L.) Karst.] roots connected to ascocarps of Morchella rotunda (Pers.) Boudier revealed that hyphae of morel were associated with all parts of the root system. The main suberized roots were surrounded by a mycelial sheath. The finer rootlets were enveloped by a cottony mycelium and their absorbing root tips were found to be ectomycorrhizal. Morel hyphae also invaded the oldest parts of a heterobasidiomycete ectomycorrhiza.