Petrocodon vietnamensis sp. nov. (Gesneriaceae) from karst caves in northern Vietnam

Petrocodon vietnamensis, a new species from karst cave in north Vietnam is described and illustrated. It is morphologically close to P. bonii, but can be distinguished from the latter by having a green, 3-6 cm long peduncle; green, ca 5 mm long calyx lobes; narrow infundibuliform, a 1.1-1.2 cm long corolla tube; ovate abaxial lip lobes; pink to white, 9.5-10.5 mm long filaments; lateral staminodes adnate to ca 12 mm above the corolla base; densely white glandular-puberulent pistil; a pink to white, 5.5-7.5 mm long style; a white stigma, and a 2-3 cm long capsule. Information on ecology, phenology, preliminary conservation assessment of the new species and a key for the taxonomic identification of Petrocodon species in Vietnam are also provided.