Studies on Micromorphology of Leaf Epidermis of Cynanchum(Asclepiadaceae) from China under Environmental Scanning Electron Microscope

The micromorphology of leaf epidermis of 29 species and 1 subspecies of Cynanchum from China were examined by environmental scanning electron microscope(ESEM).The results showed that the leaf epidermis' features of Cynanchum were similar.The cell contour of their leaf epidermis cells was usually polygonal or irregular.The abaxial epidermis of almost all but C.stenophyllum had stomata,and most of the shapes of the stomata were not sunken.Many species of Cynanchum had thick cuticular membrane on leaves.A few species were distinctively different from others in their size of stomata and ornamentation of cuticular membrane.In this paper,it is supported that C.muliense and C.steppicolum were treated as synonyms of C.forrestii in Flora of China(Vol.16),and it is not supported that C.alatum was treated as a misidentification of C.callialatum,C.cathayense as a synonym of C.acutum subsp.sibiricum,and C.komarovii as a synonym of C.mongolicum.