Abstract
The ability of Populus tremuloides Michx. to form ectomycorrhizae with identified species of fungi was investigated using a pouch technique. Twenty-nine out of 54 fungus species formed ectomycorrhizae on aspen seedlings. Aspen seems to display little specificity for ectomycorrhizal fungi. Only epidermal Hartig nets were observed in the synthesized ectomycorrhizae and periepidermal ones were frequently encountered. Structural and morphological characteristics of ectomycorrhizae are presented by genus of mycorrhizal fungi. This grouping of characters by genus seems possible independently of the host plant. The classification of ectomycorrhizae is viewed in a new way in which structural types would be taxonomically related to the genus of the fungal symbiont.