This book firstly addresses the question of what is allelopathy, as allelopathy is one of these unfortunate terms in ecology that has no unified definition. The book then examines the major episodes in the history of allelopathy: the writings from classical Greece and Rome; mediaeval Arabic, Indian and Chinese work; the advent of printing and promulgation of information in the 16th and 17th centuries; the 18th century and the theory of root excretion; the 19th century and the influence of A.P. de Candolle; the early 20th century and the work of Pickering and the USDA Bureau of Soils; and the years leading to the current era. The work draws extensively on original sources, and consequently many of the assertions published in relation to the background of allelopathy, are shown to be incorrect, or at best very inadequate. There is a great deal of information presented, in a consolidated or accessible form, for the first time. The book endeavours to set the history of allelopathy within both a scientific and sociological context.