This represents the second slide in a series highlighting the history, chemistry, and uses of ricin, a highly toxic poison made from castor beans. The slide, entitled, “Castor Plant (Ricinus communis)”, states that the castor plant, R. communis, originated in Ethiopia, and is now found in tropical, and warm, temperate regions. Ricin is a highly lethal poison, i.e. the 3rd most lethal substance known, and is now sometimes used as an agent of bioterrorism. This presentation is copyrighted by Dr. Jonathan Burstein, MD, Anthony J. Carbone, MD, MPH, of the Harvard Center for Public Health Preparedness, Harvard School of Public Health.