Abstract: Calamagrostis Adans. s.l. is a genus with variable definition in which two genera are often recognized in China: Calamagrostis s.s. and Deyeuxia Beauv. In this study, the leaf epidermis of five species of Calamagrostis s.s. and 26 species and one variety of Deyeuxia was examined under light microscopy. Although all the species examined have a Festucoid type epidermis, a number of variations of some epidermal features exist at the species level. This includes variation in morphology and wall thickness of intercostal long cells, shape and distribution patterns of stomata, morphology and distribution patterns of short cells and silica bodies, morphology, silicification, and distribution of prickles, and presence of micropapillae. Fifteen qualitative characters of the leaf epidermis were used in a phenetic analysis. No sharp differences were found between Calamagrostis s.s. and Deyeuxia. However, there are two major clusters in the UPGMA tree. The first cluster includes species with thick-walled long cells, frequent short cells and/or prickles and silicified prickles. The second cluster includes species with thin-walled long cells, infrequent short cells and/or prickles and unsilicified prickles. The results show that leaf epidermal variation is related with environment, but not concordant with any of the infrageneric classifications of the genus. Species in the first cluster are usually distributed at an altitude above 2600 m, while those of the second cluster are generally distributed at an altitude below 2600 m.

Key words: Calamagrostis, Deyeuxia, micromorphology, long cell, short cell, prickle, silification, micropapillae