Morphological characteristics of the Eucommia barks produced in Korea and China and of the barks of Euonymus japonicus $T_{HUMBERGI}$ in Korea and Euonymus pellucidifolia $H_{AGATA}$ in Taiwan were compared. The similarity in morphological features between Eucommiae Cortex produced in Korea and that of China suggests that both plants are of same botanical origin. However, the size of tissues and cells indicates that there is only one difference due to warm climatic environment. The similarity and difference of the barks of Euonymus japonicus produced in Korea and Euonymus pellucidifolia produced in Taiwan comfirmed that the two plants belong to the same genus and that they are different species.