Mycorrhizal symbioses have existed since at least the Ordovician period, between 400 and 500 MYa. Associations, and even some plant–fungus species pairs, have existed in morphologically recognized combinations through every climate and substrate condition throughout that time period. Across that vast time, virtually every potential condition likely would have been encountered. Over the past eight chapters, I have covered nearly the entire range of conditions that mycorrhizal relationships have encountered: some ancient, some novel.