Abstract: Shape and micromorphological characteristics of fruits in 19 species and 3 varieties of Polygonum sect. Persicaria from China were observed and studied under stereoscope and scanning electron microscope (SEM). The results showed that the fruits of Polygonum section Persicaria are ovoid or elliptic-ovoid, triangulate or biconcave or biconvex; attenuate at apex, with a beak or not. According to micro-morphological characteristics, the achenes can be divided into 7 types: deep or shallow hollows, cerebelloid ornamentation, paracerebroid ornamentation, reticular ornamentation, irregular plications, small verrucose ornamentation, and dense shallow reticular ornamentation. In addation, the evidence of micro-morphological characteristics of fruits supports not only the merge of P. lapathifolium L. var. salicifolium Sibth. to P. lapathifolium L., treated as synonym of P. lapathifolium L., but also the view that P. longisetum De Br. is the variety of P. posumbu Buch-Ham. ex D.Don. We also think that P. lapathifolium L. var. lanatum (Roxb.) Stew. should be resumed the rank of species. and P. longisetum De Br. var. rotunatum A.J.Li should be regarded as the rank of speices. The evidences of micro-morphological characteristics of fruits also support the exist of a new species of Polygonum pingwuense F. Z. Li et Y. T. Hou et S. J. Fan, sp.nov.

Key words: Polygonum, Sect. Persicaria, fruit shape, pericarp micro-morphology, ornamentation, China