Anatomical Investigation of Marrubium friwaldskyanum Boiss. and Marrubium peregrinum L. (Lamiaceae) from Bulgaria

The present study presents data on the anatomical characteristics of the leaf and stem in Marrubium friwaldskyanum and Marrubium peregrinum. The leaves in both species are amphistomatic with diacytic and anomocytic stomata. The leaf lamina shows differentiation of palisade and spongy tissue, and collateral vascular bundles. Non-glandular and glandular trichomes have been found on the epidermis of the leaves and stem. The non-glandular trichomes are unicellular linear and multicellular branched. Glandular trichomes are peltate, with a single-celled or two-celled structure. There is a difference between the two species in terms of the width of the epidermal cells of the stem, the thickness of the cortex, the thickness of the xylem and the phloem in the stem. The established differences in the anatomical features can be useful in future taxonomic studies within the genus Marrubium.