The natural communities of the world are diverse, and many schools of ecology have developed classifications of communities in partial independence of one another. There is consequently a vast and widely dispersed literature on the classification of plant and animal communities, comprising divergent approaches of different schools and representing a great experiment on the usefulness of different possibilities for classification. The editor sought in a re view monograph of 1962 to summarize these schools and their history, and in 1973 published a treatise on 'Ordination and Clas sification of Communities' as volume 5 of the Handbook of Vegetation Science. We were fortunate, in preparing the latter work, to have a truly international panel of authors to discuss different major ap proaches to classification. This second edition of the book of 1973 is intended to make the work more widely available in a less expensive form as companion volumes on ordination and on classification of plant communities.

A classification of Midwestern plant communities. Introduces the U.S. National Vegetation classification and explains the process used to define the 588 Midwest community types (associations). Provides descriptions of each of these plant associations and places them in an ecological context by organizing them into ecological groups.

A large part of ecological research depends on use of two ap proaches to synthesizing information about natural communities: classification of communities (or samples representing these) into groups, and ordination (or arrangement) of samples in relation to environmental variables. A book published in 1973, 'Ordination and Classification of Communities,' sought to provide, through contributions by an international panel of authors, a coherent treatise on these methods. The book appeared then as Volume 5 of the Handbook of Vegetation Science, for which R. TuxEN is general editor. The desire to make this work more widely available in a less expensive form is one of the reasons for this second edition separating the articles on ordinction and on classification into two volumes. The other reason is the rapid advancement of understanding in the area of indirect ordination-mathematical techniques that seek to use measurements of samples from natural communities to produce arrangements that reveal environmental relationships of these communities. Such is the rate of change in this area that the last chapter on ordination in the first edition is already, 4 or 5 years after it was written, out of date; and new techniques of indirect ordination that could only be mentioned as possibilities in the first edition are becoming prominent in the field. In preparing the second edition the chapter on evaluation of ordinations has been rewritten, a new chapter on recent developments in continuous multivariate techniques has been included, and references to recent work have been added to other chapters.

During the International Botanical Congress in Edinburgh, 1964, Mrs. I. M. WEISBACH-JUNK of The Hague discussed a plan for preparation by her publishing company (Dr. W. Junk B.V.) of an international Handbook of Vegetation Science. She proposed a series that should give a comprehensive survey of the varied directions within this science, and their achievements to date as well as their objectives for the future. The challenge of such an enterprise, and its evident value for the further development of vegetation research, induced the undersigned after some consideration to accept the offer of the honorable but also burdensome task of General Editor. The decision was encouraged by a well formulated and detailed outline for the Handbook worked out by the Dutch phytosociolo gists J. J. BARKMAN and V. WESTHOFF. A circle of scholars from numerous countries was invited by the Dr. Junk Publishing Com pany to The Hague in January 1966 to draw up a list of editors and contributors for the parts of the Handbook. The outline and list have served since for the organization of the Handbook, with no need for major change. The different burdens of editors and authors have compelled quite different timings for completion of the individual sections.

The nature of plant communities; Analysis and description of plant communities; Plant succession; Vegetation and ecosystem classification; Vegetation as an objective of study.