Justicia tiandengensis (Acanthaceae), a new species from Guangxi, China

<i>Justiciatiandengensis</i> (Acanthaceae), a new species from a karst cave in southwestern Guangxi, China, is described and illustrated based on morphological and molecular evidence. This new species resembles <i>Justicialeptostachya</i> Hemsl. in having elongated stems, cauline leaves, and more than one flower per rachis node, but it can be readily distinguished by its oblong, thickly papery leaf blades (vs. ovate, thinly papery); calyx 2-3 mm long (vs. ca. 6 mm long); and pubescent ovary and style (vs. glabrous). Photographs, an illustration, and a distribution map are also provided.