Primulina diffusa (Gesneriaceae), a New Species Endemic to the Karst Limestone Area in Southwestern Guangxi, China

Primulina diffusa Xin Hong, Fang Wen & S. B. Zhou (Gesneriaceae), a new species growing in rocky crevices at the foot of a limestone hill near the Sino-Vietnamese border in southwestern Guangxi, China, is described and illustrated. It is morphologically similar to P. hochiensis and P. hochiensis var. rosulata, but can be distinguished by having single-flowered cymes; short peduncle (1-1.5 cm long); narrowly elliptical to subulate bracts, 2-2.5 x ca. 0.6 mm; 1-2 cm long pedicel ; calyx lobes that are densely puberulent on both sides; and filaments that are geniculate near the middle.