Leaf surfaces as a taxonomic tool: the case of Carex section Phacocystis (Cyperaceae) in the British Isles

An investigation into the potential taxonomic value of leaf surface characteristics using large sample size and multivariate analysis was undertaken in Carex section Phacocystis. A case study examined micromorphological characters of the leaf surface for six members of the section in Britain. The six split into three groups based on distribution of stomata: Carex recta amphistomous, C. aquatilis/C. nigra epistomous, and C. bigelowii/C. elata/C. acuta hypostomous. There was considerable variation within samples in stomatal density and cell dimensions. Discriminant Analysis of nine quantitative characters clearly separated four species and a cluster of two species, C. elata and C. acuta. Multivariate analysis indicated that the intercostal cell lengths from both leaf surfaces, abaxial costal cell lengths, and widths of the adaxial costal and abaxial intercostal cells were taxonomically useful in this group and potentially of use within the genus.