Michael Pollan has spent much of his career writing about the sometimes surprising relationship between plants and humans. His newest book, “This Is Your Mind on Plants," focuses on three different plants and how they affect our brains. Opium, coffee, and mescaline could all be considered powerful drugs, or simply beautiful plants, or something much more mystical. We listen back to this conversation with Pollan in front of an audience at the Newmark Theater, as part of an event put on by Powell’s Books.