Abstract: The genus Trigonotis has 56 species, of which 33 with 5 varieties are from China. In the course of a systematic study of the genus the author observed three distinctive external characters of the nutlet, and used them in the demarcation of the section. All the species of Trigonotis have tetrahedral nutlets, but some of them are bifacial hemispherical tetrahedral (Fig. 1: 1-12), others are obtriangular tetrahedral (Fig. 1: 13-22), and still others are oblique obtr-iangular tetrahedral (Fig. 1, 23-32).

Key words: taxonomic, phytogeographic, species, Chinese