Part four of this series consists of 22 chapters by various authors. After two introductory contributions, one of which is by the editor – for whom this edition is a ‘Festschrift’ on the occasion of this 65th birthday – and the other by the late prof. Tiixen, two chapters deal with ‘taxonomic units’. Landolt’s chapter on ‘closely related taxa’ treats a problem which is probably one of the most important in this context. On the consequences of morphologically indentical ecotypes and the errors these may lead to more discussion seems to be necessary. On the use of apomictic taxa the author remarks; ‘A good example is presented by Westhoff and den Held (1969), who mention a whole series of Taraxacum taxa as character species and differential species....’. Perhaps this is something to keep in mind by the authors of the next edition of the “Flora van Nederland”. “Objects, parameters and quantification in vegetation sampling” have been discussed by: Pakarinen (sampling of boreal vegetation), Londo (the decimal scale), Oksanen (Scandinavian methods), Rabotnov (various scales), Chessel and Gautier (statistical pattern analysis of a plant population) and Knapp (considerations). Reading these separate discussions on the various “schools” in European vegetation science one may question whether this is the approach a modern handbook should need. Vegetation science is a mature branch of ecology. Since Von Post in the middle of the last century a vast discussion on the methodology of sampling has been taking place. An objective of the editors of a handbook on this subject should have been a compilation of the approaches of various geographical origins, rather than inviting scientists who are well-known to use the methods, accepted by a determinate school. The young vegetation scientist, who – given his or her problem and the scale and structure of the object – who wants to find the appropriate method without taking into account the fact whether he is a Russian or a Scandinavian or a French-Swiss, will be disappointed.