Abstract: In this paper, the biosystematic relationships of Trikeraia Bor and Stephanachne Keng in the tribe Stipeae were analysed based on the characters of external morphology of spikelet, and with the view point of combining geographic distribution and habitat conditions, the centres of the origin of the two genera also explored.The results show that the relationship between the genus Trikeraia and the genus Stephanachne is the closest among genera of Stipeae;the genus Stephanachne is more advanced than the genus Trikeraia;the T.hookeri (Stapf) Bor of Trikeraia is the most primitive species in the two genera, the T.pappi-formis (Keng) P.C.Kuo&S.L.Lu.as well as the ancient stock of S.nigrescens Keng of Stephanachne which is an extinct plant, derived from this species, while the S.pappophorea (Hack.) Keng and the S.monandra (P.C.Kuo&S.L.Lu) P.C.Kuo&S.L.Lu which are other two species of Stephanachne might derived indirectly from the ancient stock of S.negrescens Keng;both the genus Stephanachne and the genus Trikeraia originated from Xizang of China, of which the former probably in western Xizang and the latter in eastern Xizang.

Key words: Trikeraia, Stephanachne, Biosystematic relationship, Geographic distribution