Diagrams have long been used to describe, claim, and produce the relatedness of human individuals and groups, animals, and plants. The tree form seems to have attained particular dominance, both within specific domains of practice and in historical scholarship. This pertains, moreover, to representations of non-organismic entities that draw from and flow back into the broad cultural history of the tree. And yet a wide variety of diagrams have been devised, sometimes in connection with the tree, other times as an explicit alternative, or as a novel or idiosyncratic invention. This volume, which brings together a commensurately diverse mix of historians of the natural and human sciences, social historians, philosophers, and historians of art and media, wishes to bring the variety of diagrammatic forms out from under the “shadow of the tree” – while also taking seriously the ubiquity of the tree and its implications.