Abstract: This paper reports the SEM(Scanning Electron Microscope) studies on the petals of medicinal species of Swertia and Halcma in China, viz., Swertia bimaculata Hook. f. et. Thoms, ex C. B. Clarke; S. angustifolia Buck-Ham. ex D. Don; S. tenuis T. N. Ho et S. W. Liu; S. macrosperma (C. B. Clarke) C. B. Clarke; S. punicea var. lutesccns Franch. T. N. Ho; S. cincta Burk and Halenia corniculata (L.) Cornaz.It is found that the surface features including the primary and secondary ornamentations, e. g. the reticulate, lophate and excrescence ones and the curvatura of the outmost periclinal epidermis cell walls etc., differ from one another with some taxonomic significance at genus, species and variety level. The results may provide new proof and suggestion to the original classification. The characters of the species are described in detail with SEM photographs and a diagnostic key is also presented briefly.

Key words: Swertia, Halenia, Petal, Surface ornamentation