One of the objects of the Biological Field Station ”Weevers‘ Duin” at Oostvoorne is the investigation of dune slack vegetation. An aspect of this study is a typology of the vegetation types; an important point of this is the relationship between the environment and the vegetation and the similarities, or differences, between the elements of the system. The island of Voorne, the dunes of which are in the area of calcareous dunes of the Netherlands, is outstandingly rich in slacks, primary as well as secondary ones. Representatives of both kinds, of all ages between young and relatively old, are found. The relation between vegetation and soil development was discussed at one of the previous meetings.