Eddy V AN DER MAAREL This volume is the first of two volumes covering the Sym­ computer programmes for the rapid clustering and ordina­ posium 'Advances in vegetation science', which was held at tion of very large sets of reI eves and for (subsequent) table Nijmegen, The Netherlands, from 15-19 May 1979. This rearrangement (this volume as well as the book Data­ symposium was organized on behalf of the Working Group Processing in Phytosociology contain various new pro­ for Data-Processing of the International Society for Vege­ grams). What we do not have is a manual in which the tation Science. After this group held its final meeting two apparently successful methods are compared and applied years earlier it decided to continue its activities, but within a to some data-sets. H. Lieth, editor-in-chief of a new Junk wider scope. Most members of the Group felt that the series 'Tasks for vegetation science' already suggested to original aim, i. e. the introduction of data-processing and produce such a manual in this series. multivariate methods for use in the systematic description The present volume contains the texts of the lectures and of plant communities, was more or less fulfilled. The book most of the poster demonstrations of the first three sessions Data -Processing in Phytosociology, largely based on papers of the Symposium, dealing with classification and ordina­ in Vegetatio, edited by E. van der Maarel, L. Orloci & S.