Breynia phongquangensis (Phyllanthaceae), a new species from Vietnam.

The new species Breynia phongquangensis from Vietnam is described and illustrated. The new species is compared with three similar species in an identification key and a table of detailed morphological characters. Breynia phongquangensis differs from the morphologically similar species B. macrantha, B. phuongiana, and B. spatulifolia by a unique combination of characters, including fleshy sepals in the staminate flowers (vs. non-fleshy in the other three species); staminate flowers 4.9-5.8 mm in diameter (vs. ca. 3.3 mm in B. spatulifolia); outer sepals of pistillate flowers 3.7-4.6 mm long (vs. 6-7 mm long in B. macrantha); and a markedly longer ovary, 3.7-4.9 mm long (vs. < 2.8 mm long in the other three species). It further differs in having fruits ca. 27.0 mm long (vs. ≤ 25.0 mm long in the other species), pistillate flower pedicels 16-53 mm long (vs. 2.5-4.0 mm long in B. phuongiana and 0.3-3.0 mm long in B. spatulifolia), globose fruits (vs. starfish-shaped in B. phuongiana), and fewer lateral veins (6-8 pairs vs. 9-15 pairs in B. spatulifolia).