Ethnobiology is the scientific study of the way plants and animals are treated or used by different human cultures. Ethno medicine is a sub-field of ethno botany or medical anthropology that deals with the study of traditional medicines: not only those that have relevant written sources (e.g. Traditional Chinese Medicine, Siddha, Ayurveda), but especially those, whose knowledge and practices have been orally transmitted over the centuries. Ethno medicine is concerned with the study of medical systems from the native's point of view. Native categories and explanatory models of illness, including aetiologies, symptoms, courses of sickness, and treatments are investigated. The ethno medical approach proves particularly useful for the study of indigenous therapeutic agents because it allows the researcher to understand treatment patterns according to native explanatory models instead of only through the lens of biomedicine. This book gives an account of medicinal plants of all the countries on planet earth.