The ecology and the syntaxonomy of the following Belgian and French Lolio-Potentillion anserinae communities are described: 1. Ranunculo-Alopecuretum geniculati 2. Basal community of Agrostis stoIonifera-[Lolio-Polentillion anserinae] a) Juncus inflexus-Carex olrubae type b) Eleocharis uniglumis-Carex olrubae type c) Trifolium fragiferum-Carex hirta type 3. Triglochino-Agrostietum stoloniferae ranunculetosum repentis 4. Nasturtio-Alopecurelum geniculati ranunculetosum scelerati 5. Agrostio-Trifolietum fragiferi a) subassociation typicum b) subassociation inops The syntaxonomical position of Carex otrubae and Eleocharis uniglumis is discussed, leading to the conclusion that both species are character-species of the association group with Eleocharis uniglumis. The two main ecological factors are elucidated with the help of a P.C.A. ordination diagram