Taxonomic studies of Blachia (Euphorbiaceae) in China (I): B. chunii is synonymous with B. cotoneaster, not B. siamensis

Blachia chunii (Euphorbiaceae), described from China, has been previously placed in synonymy with B. siamensis. Critical observations on herbarium specimens (including type material) and living plants in the wild revealed that B. chunii is actually identical with B. cotoneaster, not B. siamensis. We therefore reduce B. chunii to the synonymy of B. cotoneaster. Blachia siamensis should thus be excluded from the flora of China and B. cotoneaster is newly recorded for the flora of China. Illustrations of all three species, and a distribution map of B. cotoneaster and B. siamensis are also provided. Lectotypification is proposed for B. cotoneaster.