This volume in the international series of books of the World University Library aims te* provide a broad introductory, not too specialized survey of the historical background and tho latest results of plant variation studies. In the authors’ opinion there are signs that in an age of molecular biology the traditional branches of biology are looked upon as outmoded. Of course they disagree with this view, and give a survey of the increasingly scientific development of the study of plant variation and evolution during the last two centuries. Topics discussed in the 14 chapters include: the historical background (from Ray to Darwin; early work on the description and basis of varation), modern views on the basis of variation, evolution in populations, the variation and breeding behaviour of gamodemes, the nature and origin of species, intraspecific variation, gradual speciation and hybridization, polyploidy, and evolution. In the last chapter, entitled “How to take the subject further”, valuable suggestions how to contribute to the knowledge of organic variation are made to both biologists and interested amateur naturalists.