A compilation of research from around the globe that documents a diversity of fungi and the critical roles they play in forest health and function. The intricacies of fungal form, function, interaction, evolutionary history, and geographic distribution are brought to light for over 1500 taxa (17 new) of fungi, lichens and myxomycetes. A series of 28 contributions on tropical, temperate deciduous, boreal coniferous forests, and the microsilve of the Arctic are presented.