Abstract:The leaf epidermis and the epidermal hair of 46 species and 3 varieties of Begonia L.from Yunnan have studied by SEM for the first time.Their characters are classified and terminologized.The epidermal cell morpha can be divided into six types(multiangle,irregular oblate,sheroid,papillate,and conical).The cuticle layer of epidermal cell can be divided into six types(smooth,tuberulate,reticulate,striped,cornet,and spiral).The morpha of trichome cell can be divided into four types(spuare,multiangle,oblong,and elliptic).The cuticle layer of trichome cell can be divided into four types(smooth,tuberculate,piliferous,and cornute).The epidermal hair can be divided into three categories,and six types(uniserial:lanes and pubes,complex hair,multiseriate:tubercular-based seta,conical seta and rough hair).The result shows that combination of various characteristics for epidermal cell and its hairvaries from species to species.Therefore,they can be used as taxonomic evidence in the classification of species and varieties.However,without identical characteristics in each section,they are not significant in distinguishing sections.Nevertheless,in Sect.Begonia,the diversity of epidermal cell and its hair my indicate that it has some relationships with some other sections,Through the analysis of the relationships between hair occurrence and plant living environments,it is proposed that Sect. Coelococtron may be more primitive than the others and possible evolutionary relationship of various sections from Yunnan is inquired.