Abstract
Nutlets of 13 taxa of subfamily Cyperoideae (Cyperaceae) from Egypt were investigated using light and scanning electron microscopes to ascertain the taxonomic utility of the nutlet in corroborating and elaborating on distinctions between closely related genera and species. The studied taxa included representatives of tribes Fuireneae, Cypereae, Cariceae, Abildgaardieae and Schoeneae. Nutlet shape, size, color, surface, epidermal cell shape, anticlinal boundaries, outer periclinal cell wall and relief of outer cell walls were provided. It was found that the epidermis has useful microscopic characters to help in the taxonomic assessment of Cyperoideae. Seven different types of anticlinal cell wall boundaries were described, four types of outer periclinal cell walls, and five different forms of the secondary cell walls were recognized. A diagnostic key for the studied taxa based on nutlet characters was presented. The results showed congruence between the UPGMA dendrogram and principal component analysis in suggesting two major groups and six subgroups. The most important characters with the highest factor loadings along the first two PCA axes included nutlet shape, nutlet apex, surface topography and the presence of silica bodies. The results of this study confirmed the heterogeneity of the Cyperoideae and indicated that Fuireneae is the most heterogeneous tribe.