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The stem and leaf anatomical studies of three species namely Vernonia amygdalina Del. (Bitter leaf and Non- bitter leaf variety), Cyanthillium cinereum (L.) H.Rob and Brenandendron donianum (DC.) H.Rob. were undertaken with the aid of a light microscope to ascertain their taxonomic relationship. The anatomy of the stem showed a single layer of epidermis in all the taxa studied, 2-3 layers of collenchyma cells in V. amygdalina, 4-5 layers in C. cinereum and B. donianum. The vascular bundles are arranged in a concentric manner in V. amygdalina and C. cinereum while it is scattered in B. donianum. The scattered vascular bundles and absence of pith in B. donianum which is a characteristic feature of the monocotyledonous plant is unique and could be exploited for taxonomic purposes. The occurrence of bicollateral vascular bundles in B. donianum and open collateral in the other taxa studied could be of diagnostic importance. The anatomy of the midrib also showed a single layer of epidermis usually covered with a cuticle in all the taxa studied. The outline of the midrib is oblong in all the taxa studied. The bundle sheath consists of a cap of 1-3 layers of thick- walled sclerenchyma in B. donianum and thin-walled parenchyma in C. cinereum and the two different taxa of V. amygdalina. The collenchyma cells are 2 – 3 layers in V. amygdalina, 4-5 layers in C. cinereum and B. donianum. The vascular bundle is bicollateral in B. donianum and collateral in the other taxa studied. The variation in the type and arrangement of vascular bundles in the midrib is also of taxonomic importance. The similarities in the anatomy of the stem and leaf of V. amygdalina (bitter leaf) and V. amygdalina (non bitter leaf) suggest that the two taxa are the same species.