Arbuscular Mycorrhizal Fungi
VAM fungi belong to the Glomeromycota.
They are primitive fungi at the base of the tree for higher fungi (basidiomycetes).
They associated with first land plants and appear to have evolved very slowly since then.
They have no known sexual state.
They produce microscopic structures, or relatively small sporocarps (truffle-like).
Just over 200 species of these fungi are described, yet they are capable of forming mycorrhizal associations with the majority of plants.