Scanning electron micrographs of leaves of British Carex species, 4. Subgenus Carex: sections Paludosae, Porocystis, Atratae, Paniceae, Pachystylae, Glaucae, Ceratocystis and Strigosae

Abstract This part includes about a third of the large Subgenus Carex, embracing sections Paludosae, Porocystis, Paniceae, Pachystylae, Ceratocystis and Strigosae. These are mostly plants of unwooded habitats, although C. pallescens (section Porocystis) is often associated with woods, and C. sylvatica and C. strigosa (section Strigosae) are characteristically woodland plants. At least three of the sections in this part (Atratae, Paniceae, Ceratocystis) appear to be natural on morphological and molecular criteria. As in subgenus Vignea, micromorphology clearly differentiates between several species-pairs (acutiformis/riparia, panicea/vaginata, hostiana/flava-group), but makes only a limited contribution at sectional level. Carex pallescens is closely linked with C. acutiformis in molecular analyses. Carex filiformis seems to have its phyletic affinities with Paniceae rather than with Acrocystis. In Ceratocystis, C. hostiana is clearly marked off by its papillose lower leaf surface from the C. flava group which, though variable, appear to be substantially uniform micromorphologically. Carex sylvatica has a close link with Ceratocystis in molecular analyses. As in subgenus Vignea, many species, particularly in the flava group and Strigosae, show minor variations on a common pattern, the ‘default caricoid leaf’.