Two new species of Platanthera (Orchidaceae, Orchidoideae) from Xizang, China

Two new orchid species, Platanthera linzhiensis , P. deergongensis , are described and illustrated from Motuo, Xizang, China. P. linzhiensis is closely related to P. uniformis , but differs from it by lip yellowish green, spur yellow, nearly as long as ovary, connective obtuse -truncate, not protruding from anther, column lateral appendages ovate to oblong, slightly shorter than the anther. P. deergongensis is morphologically similar to P. contigua , but is distinguished from it by having white lip, obtusetruncate connective and ovate to oblong column lateral appendages. Molecular phylogenetic analysis based on six markers (nrITS, psaB , matK , psbA-trnH, rbcL , trnL-F) revealed that P. linzhiensis and P. deergongensis formed a clade with high support, and are close to P. superantha .