Morphological characters and anatomical investigations were used in this study as a taxonomic evidences to evaluate the relationships between 4 species representing 3 genera of Mimosaceae and Caesalpiniaceae. These species were; Leucaena leucocephala (Lam.) De Wit., Bauhinia variegata L., Bauhinia alba Buch-Ham and Delonix regia Bojor ex Hook. Morphological results indicated that, both species of genus Bauhinia were exceeded in most studied traits of the axis (stem and root) than other genera, where D. regia exhibited increment for most leaf characteristics (except leaves no.) over the other species. L. leucocephala showed remote values for most morphological traits than other genera. Anatomical studies confirmed differences between the 4 species in most studied traits. Increase in plant height was mainly related to number of cells more than to lengths. Stem diameter increasing was mainly attributed to the increasing in secondary xylem thickness more than other tissues.