William C. Darrah was an avid correspondent. He genuinely enjoyed the exchange of ideas with paleobotanists throughout the world. In 1932, while still a student at the University of Pittsburgh, Darrah began what became a 20-year history of sharing ideas, reprints of publications, and specimens with European paleobotanists. The W. C. Darrah correspondence files—from which this historical account is mainly taken (supplemented by his correspondence in European files)—contain a record of the details of the paleobotanical pursuits of many of the early-twentieth-century European paleobotanists, especially P. Bertrand, W. J. Jongmans, and R. Florin, with whom he had the most extensive correspondence and contacts. The correspondence also contains a record of the shipments and receipts of the plant-fossil exchanges between Darrah and the European paleobotanists.