The section Ceratocystis (Carex, Cyperaceae) in the Netherlands

All the material of Carex section Ceratocystis kept in the herbarium of Naturalis Biodiversity Center in Leiden (L), to be precise 1412 sheets, has been revised in order to get a better understanding and more complete overview of the occurrence of the native species and hybrids within this section in the Netherlands. The hybrid material from the Hussenberg near Beek (Province of Limburg), which was known in literature as C. ×luteola [C.distans × C. flava] belongs in our opinion to C. ×xanthocarpa [C. flava × C. hostiana]. A key for determining all species and hybrids within the section Ceratocystis occurring in the Netherlands has been provided. Besides, this study shows that it is important to continue collecting material for Naturalis, Leiden.