Objective: To accumulate taxonomic data of the leaf epidermal features of the medicinal species of Euonymus.
Method: Twenty-nine materials of 21 taxa (including 16 species, 4 varieties and 1 form) representing 5 sections of Euonymus are examined by using both of light microscopy and scanning electron microscopy.
Result: The form of epidermal cells in Euonymus is usually polygonal or irregular. The stomata were anomocytic in all the species examined except E. maackii and E. bungeanus var. semipersistens. Stomatal types of all species studied may be anomocytic, anisocytic, cycolocytic or the transitional types among them.
Conclusion: The results show that some characteristics (including cuticular membrane, shape of guard cells, inner margin of outer stomatal rim, outer stomatal rim and stomata type) of the leaf epidermis can provide some anatomical evidence for the classification. The characteristics of leaf epidermis support following treatments: E. acanthocarpus var. longipes, E. acanthocarpus var. scandens and E. acanthocarpus var. sutchuanensis should be merged into E. acanthocarpus; E. bungeanus var. semipersistens should be merged into E. maackii; E. hamiltonianus f. lanceifolius should be merged into E. hamiltonianus.