Introduction
The genus Cerastium L. in the broad sense consists of nearly 100 species mainly distributed in temperate and cold regions, with 23 species occurring in China (Lu and Morton 2001). Traditionally, the genus was subdivided into two subgenera: Cerastium (characterized by five carpels, five styles and ten capsule teeth) and Dichodon (Bartl. ex Rchb.) Boiss. (characterized by three carpels, three styles and six capsule teeth) (Schischkin 1970). In a recent molecular phylogenetic study (Greenberg and Donoghue 2011), the subgenus Cerastium was supported as the sister-group of Moenchia Ehrhart., a clade with four styles and eight capsule teeth, while the other subgenus Dichodon was sister to Holosteum L., which has three styles and six capsule teeth. Based on these results, Hernández-Ledesma et al. (2015) accepted the subgenus Dichodon at the generic level and reinstated it as Dichodon (Bartl. ex Rchb.) Rchb. in their comprehensive taxonomic study of Caryophyllales. In the Flora of China, two species (viz. Cerastium cerastoides (L.) Britton and C. parvipetalum Hosok.) belonging to the subgenus Dichodon were accepted (Lu and Morton 2001). The former species has already been transferred to Dichodon (Dichodon cerastoides (L.) Rchb.) by Reichenbach (1841), while the other species, endemic in Taiwan, has not been formally transferred to Dichodon. Accordingly, the new combination Dichodon parvipetalum is proposed below.