Scanning electron micrographs of leaves of British Carex species, 1. Introduction and some common sedges

Abstract Scanning electron micrographs are presented of ten species of Carex, illustrating the range of leaf characters displayed by this technique. Leaf-surface characters include the distribution and form of the stomata on the two surfaces, whether they are flush with the leaf-surface or sunk in pits or hidden amongst papillae, and the size, texture and ornamentation of the epidermal cells on the two surfaces of the leaf. Most Carices have their stomata mainly on the underside of the leaf (hypostomous); C. nigra and C. rostrata have most of their stomata on the upperside (epistomous); and C. canescens has stomata on both leaf surfaces (amphistomous). Stomatal distribution can be seen with a hand lens and is a useful field character. The stomata in many species are flush with the smooth leaf surface but, in C. flacca and C. panacea, they are hidden among the closely-set papillae covering the lower leaf surface. In C. rostrata, they are surrounded by papillae on the upper surface in contrast to C. vesicaria, where they lie flush with the smooth lower surface. The presence of forward-pointing teeth on the upperside of the leaves of C. pilulifera is a striking feature in scanning micrographs, in contrast with the smoother surface of C. caryophyllea. Of the needle-leaved species, C. dioica has one broad band of stomata on each side of the leaf, but C. pulicaris has two narrower rows; this character can be seen with a good hand-lens in the field.