The method of characterizing mycorrhizal fungi according to mantle structure and hyphal features is briefly discussed in relation to other methods of identifying tree-fungus combinations and is shown to be complementary to them. The need to search for and apply as many criteria as possible when making distinctions, and conversely to refrain from erecting categories where there are insufficient data, is stressed. Comprehensive descriptions, adequately illustrated, are necessary. Eight distinctive types of eucalypt mycorrhiza are selected and described. Two features which do not appear to have been used elsewhere are shown to be valuable in making distinctions: the anatomy of fungal rhizomorphs, and the tissue structure of the mantle as revealed in plan view by cleared whole mounts.