Two New Dimorphic Species in the Endogonaceae:<i>Glomus Ambisporum</i>and<i>Glomus Heterosporum</i>

Two new vesicular-arbuscular (VA) mycorrhizal fungi (Endogonaceae) from Florida, Glomus ambisporum and G. heterosporum, differ from all previously described species in the production of two distinct spore types. Black sporocarps or sporocarp aggregates of Glomus ambisporum are produced in the soil and hyaline spores are formed within host tissues. The outer wall of sporocarpic spores is subhyaline with a faint reticulum of hexagonal plates. Glomus heterosporum has light to dark brown sporocarps or sporocarp aggregates produced externally to host tissues and forms hyaline spores within host tissues. The outer wall of the sporocarpic spores is hyaline, smooth, and evanescent. Sporocarps of both species have spores radially arranged around a central hyphal plexus which resemble sporocarps of Sclerocystis rubiformis. This is the first report of dimorphism in the genus Glomus.