Comparative anatomy of stems and leaves of plectranthus L. (Lamiaceae) in Saudi Arabia and systematic implications.

A comparative anatomical study of the Plectranthus species growing in Saudi Arabia by using light microscopy method in order to evaluate their diagnostic value for systematic studies. Macro- and micromorphological characters, including stem, leaf, petiole anatomical, and trichome structures are presented. Descriptions of stem shape in cross-section, epidermal cell shape, cortex, pith, vascular bundles, leaf shape in cross-section, mesophyll, types and distribution of trichomes are presented.