Arbuscular mycorrhizas are the most common and widespread form of mycorrhiza. They are characterised by the presence of arbuscules in cortical cells of the root. The arbuscules are linked by either intercellular or intracellular hyphae within the root to mycelium in the surrounding soil. Some fungi form rounded storage structures called vesicles or spores in the root tissue or soil. LINK
Ectomycorrhizas are characterised by a sheath or mantle of hyphae surrounding the root. Lateral projections of the mantle may penetrate between epidermal cells of the root in what is called the Hartig net. LINK
Ericoid mycorrhizas are characterised by the penetration of epidermal cells of the fine hair roots by fungi. Coils are formed in these cells and the fungi do not spread from cell to cell. LINK
Orchid mycorrhizas are characterised by hyphal coils in cortical cells of root-like tissue or the collar of the shoot. The fungus penetrates through passage cells of the exodermis and hyphae ramify through the cortical tissue by intracellular penetration. Coils collapse over time. Cells may be colonised by more than one hypha on more than one occasion. LINK
Ectendomycorrhizas are characterised by the formation of a sheath on the root surface, with intracellular penetration of and coil formation in cortical and epidermal cells beneath. A Hartig net may be present.
Other types of mycorrhiza have been found, often in single plant species or genera with fungi known for form typical mycorrhizas in another plant group. LINK