Taxonomy and comparative anatomical studies of Viola sect. Sclerosium (Violaceae) in Iran

Abstract The comparative anatomy of three morphologically close taxa of Viola sect. Sclerosium W. Becker distributed in southern Iran is presented in this study: Viola behboudiana, Viola cinerea and Viola stocksii. Cross-sections of roots, stems, peduncles, petioles, leaves and the surface sections of leaves showed that the following properties were taxonomically informative: number of collenchymatous cell layers in the stem, presence or absence of cortical bundles in the stem, number of vascular bundles in the peduncle, presence or absence of calcium oxalate crystals in the peduncle cortex, presence or absence of trichomes on the epidermis of the peduncle, shape of collenchyma cells in the petiole, and midrib outline of the leaf. Numerical analysis (unweighted pair-group method with arithmetic averages, principal components analysis) of 55 qualitative and quantitative characters confirmed the delimitation of three taxa.