Trichome Micromorphology of Egyptian Ballota (lamiaceae) with Emphasis on Its Systematic Implication

Trichomes of 5 taxa of the genus Ballota were examined by using light and scanning electron microscopy. The indumentum shows considerable variability among different species, and therefore, affords valuable characters in delimitation of species. The characters of taxonomic interest were presence of glandular and non-glandular trichomes, number of cells (uni-, bi-, trior multi-cellular), presence of multicellular branched trichomes and existence of branched (dendroid and stellate) trichomes. Two basic types of trichomes can be distinguished: glandular and non-glandular trichomes. The glandular trichomes can in turn be subdivided into two subtypes: stalked and sessile. The stalks of the glandular trichomes can be uni-, bi-, trior multi-cellular. In addition to presence of epidermal prickles, the non-glandular trichomes are classified also according to number of cells into uni-, bi-, tri-, multicellular, stellate and dendritic trichomes. Some of non-glandular trichomes may be branched or unbranched. Two keys are constituted according to both glandular and non-glandular trichomes. Overall, trichome micro-morphology is more useful in separation of Ballota species.