Peter H. Raven, President Emeritus of the Missouri Botanical Garden, is George Engelmann Professor of Botany at Washington University in St. Louis and an adjunct professor of biology at the University of Missouri–St. Louis and at St. Louis University. He was president of Sigma Xi for 2003-04 and has been a member of Sigma Xi for 45 years. Raven received the National Medal of Science for his contributions to the fields of biodiversity and the environment. A member of the National Academy of Sciences and former NAS home secretary, he chairs the National Research Council's Division of Earth and Life Sciences. While at Stanford University in the early 1960s, he and Paul Ehrlich developed the theory of coevolution, which was originally based on the relationship between butterflies and plants. This concept has been a highly fruitful one, inspiring many thousands of subsequent papers and becoming a CitationClassic. Raven is a co-founder of the Flora of China project, an effort to produce a descriptive encyclopedia of the 30,000 different plants there, involving the collaboration of botanists from throughout the world. His role as a leading environmentalist and global team builder has brought him membership in the national academies of many countries.His many honors include the International Prize in Biology from the government of Japan and the Volvo Environment Prize. Raven has also been president and chair of the board of directors of the American Association for the Advancement of Science.