Abstract: The genus Atraphaxis is found mainly in gravel steppes, sandhills and stony slopes or desert, with only a few species in meadow or river valleys. In China there are two sections and eleven species (including three varieties), which are distributed mainly in the northwest, with a few in the northeast and the north. Characters of the genus were compared and analyzed in the present work. Outer perianth segments 2, small, reflexed in fruit, inner perianth segments 2 or 3, large, erected and enveloping the nut. The embryo is curved, but those in the other genera of Atraphaxideae are straight. The curved embryo is the primitive character, because most species of the order Caryophyllales are of a circular embryo, which is belived to be ancestral in the Polygonaceae. The Pollen ornamentations of Atraphaxis are striate or striate-reticulate, different from those of the other genera. A new system of the tribe Atraphaxideae in proposed in the present paper. Based on the character analysis of the species in China, the present authors believe that Sect. Tragopyrum is more primitive than Sect. Atraphaxis. According to the distribution, the genus Atraphaxis might originate in Kazakstan, where not only are most species found, but also the most primitive species, like A. muchketovii, as considered by A. N. Krasnov, are found. Central Asia is considered as the distribution centre and origin centre of thegenus Atraphaxis.

Key words: Atraphaxideae, Atraphaxis, system, pollen