Those pale button mushrooms in your supermarket hardly do justice to the diversity of fungi. The world hosts an incredible array of these important organisms—and mycologists are discovering more than 2000 new species a year, including ones that live on driftwood, bat guano, and even an oil painting. That’s according to a new report, titled State of the World’s Fungi, from the Royal Botanic Gardens, Kew, a botanical research institution in Richmond, U.K. The lavishly illustrated overview covers the usefulness of fungi (think beer, bread, and penicillin, for starters) as well as the serious threats that some fungi pose to...