Abstract: The external morphology of the major species of sects. Elymus, Turczaninovia and Macrolepis in Elymus was analyzed, the similarities and the differences of the external morphological characteristics were summarized, and the taxonomic significance of external morphological features among them was discussed. Furthermore, according to the evolutionary trends of external morphological characters including inflorescences, spikelets, florets and paleas of three sects, their evolutionary positions and relationships were analyzed. The results show that the sect. Elymus is most primitive among three sects, the sect. Turczaninovia is advanced than the sect. Elymus, and the sect. Macrolepis is the most advanced sect. The sect. Elymus probably generated the sect. Turczaninovia, whereas the sect. Macrolepis was probably derived from the sect. Turczaninovia. The biosystematic relationships of tested species in Elymus were also discussed. The research provides the theoretic foundation for further studying the systematics and evolution of Elymus.

Key words: sect.Elymus, sect.Turczaninovia, sect.Macrolepis, external morphological characteristics, biosystematic relationship