T is the task of biogeogrjhy to describe and explain the distribution of organisms I on earth. The use of maps as basic tools is inevitable, but, so far, vegetation maps have contributed little to studies of a world wide character. It is no longer possible to investigate the vegetation of an area without considering that of the neighboring regions, of the whole continent, and, in fact, of the world. It has been shown repeatedly, as for instance by Meusel (1943) in his masterful presentation and by Kfichler (1946) that comparative studies are fundamental, but existing vegetation maps do not at the present time permit detailed scientific comparisons of widely separated areas because there is at present no method of mapping vegetation which allows a comparative approach. The study of vegetation or plant sociology has shown great advances in the course of this century and yet it has proved inadequate to solve the basic problems of phytogeography. Even the most advanced system developed by plant sociologists, that of Braun-Blanquet (1928), is ungeographic. It therefore became necessary to devise a more natural classification of vegetation which avoids rigidity, permits world-wide comparisons, and is adapted to mapping. Such a classification is here submitted as a basis for further investigations, be they local or global in scope, and above all as a foundation for unified cartographic work. In developing this classification the author had the following principles constantly in mind: it must be applicable to all types of vegetation in all regions of the earth and must be adaptable to all map scales. Also, the system must not only be so flexible that it can fulfill the above conditions; it must be so clear and simple that all investigators can use it and produce the same results. Thus, two vegetation maps of contiguous areas compiled by different authors should fit together at their common margin. Unfortunately this occurs very rarely at the present time, largely because a universally applicable classification has not been developed. In offering a new method of classifying and mapping the vegetation of the world, the author does not wish tQ minimize the efforts of those who have paved the way for the final development of a solution. Toward the end of the 19th century Grisebach (1884) first published his Die Vegetation der Erde and Schimper (1898) his Pflanzengeographie auf physiologischer Grundlage. The latter work has had a much enlarged and revised third edition in 1935 (Schimper-von Faber, 1935) and must be considered one of the corner stones of modern plant geography. Just before this, Du Rietz (1931) published his important work on life forms. Whereas all these men approached their problems primarily from a purely scientific point of view, there has been at work recently a growing number of men in various parts of the British tropics with an interest in the more immediate practical value of vegetation, especially from the viewpoint of forestry. Significant contributions