This work is focused on general knowledge about mycorrhiza, its physiology and processesbetween plant and fungus before and during the colonisation of a plant root. However, the mainfocus is on ectomycorrhiza, one of the mycorrhizal symbiosis, because from a forestry point ofview it is the most important and the most common type of mycorrhizal symbiosis. The analysisof factors affecting the life of mycorrhizal symbiosis is provided in my thesis as well as theinfluence on the outer environment. My work says about the specialization of some fungi speciesin a particular tree and in our native tree species as well, which create mycorrhizal symbiosis.There are mentioned some advantages for growing of seedlings in unfavourable conditions incomparison with seedlings without any mycorrhizal symbiosis. There are also descriptions ofcollection, identification of mycorrhizal fungus, reasons why it is good to create herbarium andwhat parts of the sporocarp are the most important for the identification of mycorrhizal fungi.