Abstract: Based on the microscopic characters of epidermis of leaf blade, transverse section of leaf blade, pollen and starch grain, the systematic position of the genus Sinochasea which is an endemic genus on the Qing-Zang Plateau has been studied in the present paper. According to the information of related taxa of this genus furnished by professor Yi-li Keng, the control experiments of Duthiea brachypodia (P. Candargy) Keng et Keng f. of Aveneae, Stephanachne paposhorea (Hack.) Keng of Stipeae, Dewuxia moupinensis (Franch.) Pilger and Calamagrostis epigeios (L.) Roth of Agrostideae, which were chosen as examined species representing these tribes in this paper have been made. The results show that the difference between the S.trigyna Keng and the D. brachypodia (P. Candargy) Keng et Keng f. in the above-mentioned microscopic characters is the smallest, the difference between the S. trigyna Keng and the S. pappophorea (Hack.) Keng is secondary, and the difference between the S. trigyna Keng and the D. moupinensis (Franch.) Pilger or the C. epigeios (L.) Roth is the biggest among these species; in systematic position, the genus Sinochasea should be in the tribe Aveneae the D. brachypodia (P. Candargy) keng et Keng f. belongs to, but not in the tribe Stipeae or Agrostideae; the tribe Aveneae is more primitive than the tribe Stipeae or Agrostideae inphylogenetic development, and the latter two tribes maybe derive from the tribe Aveneae directly or indirectly.

Key words: Sinochasea, Epidermis of leaf blade, Transverse section of leaf blade, Pollen, Starch grain, Systematic position