This book had its beginnings about thirty-five years ago, when I migrated to Australia from Canada, and began a doctoral study concerning the role of allelopathy in forests of the eucalypt known in Australia as mountain ash (Eucalyptus regnans), under the supervision of Dr Kingsley Rowan and the late Dr David Ashton. In first assembling materials for the usual survey of the relevant literature, I came to realise that the relative youth of Australia as a nation and its geographical remoteness were to be barriers in fully dealing with historical concepts. At times, the simplest option was to buy the requisite antiquarian books, if they were not readily available from local libraries. I remember that one of the first such works that I acquired was de Candolle’s Physiologie Végétale, and it was then that I began to learn that the history of allelopathy had been only superficially investigated. Allelopathy is a topic which has been very much in the limelight of plant ecology in the past few decades. It is a controversial topic which has a surprisingly large body of literature associated with it, yet the mere existence of allelopathy as an ecological process is still considered doubtful by many. Most students of allelopathy seem to have assumed that the topic has been c- menced in 1937 with the work of Hans Molisch, or to those more historically minded, the theories of A. P.