Breynia mirabilis (Phyllanthaceae), a New Cauliflorous Pachycaul Species from Yunnan, China

Breynia mirabilis Y.H. Tan, Y.E. Wang & Z.X. Ma (Phyllanthaceae), a new cauliflorous species is described from the tropical monsoon rainforest occurring in humid ravines of south-eastern Yunnan, China, and diagnosed in comparison with B. beillei. The new species is placed in subg. Sauropus and is readily recognised by its unique monopodial pachycaul habit and cauliflorous, racemose inflorescence. It differs from B. beillei in its shorter inflorescences and pedicels, as well as yellow to light green staminate flowers with unswollen calyx lobes vs. pinkish staminate flowers with swollen calyx lobes mottled red. We discuss the floristic association of B. mirabilis and two other cauliflorous pachycaul species and especially their adaptation to the rainforest environment of the Pan-Gulf of Tonkin flora.