Comparison of type specimens of A. gerdemannii and A. appendicula revealed the spores to be identical in organization and subcellular structure, indicating they are conspecific. The Glomus morph of A. appendicula was not assigned a name in the protologue, but 11 living cultures started from or producing spores of A. gerdemannii also generated Glomus-like spores of identical morphology to those in type specimens of Glomus leptotichum. These spores were indistinguishable from those in type specimens of G. fecundisporum, indicating they are conspecific. Both species were described in the same paper, so the name G. leptotichum is given priority because type specimens are in better condition and specimens from a reference culture have been identified by an author of both prologues. Absence of a teleomorph and confirmation of dimorphism from single and multiple-spore inoculations of host plants in culture provide the basis for designating A. gerdemannii and G. leptotichum as synanamorphs of one vesicular-arbuscular mycorrhizal fungus.