Burmannia coerulea is described in Averyanov (2005) from limestone grounds in northern Vietnam. It is endemic to its type locality. B. coerulea differs from its closest relative B. unguiculata by its size (10 - 20 cm vs. 5 - 10 cm), more blueish stems, scale leaves and flowers (light blue to white in B. unguiculata), and a less dense scale leaf cover at the stem base. Moreover, B. coerulea has bigger flowers in comparison to B. unguiculata (although still small compared to other Burmannia sp. in Vietnam), and the latter species has caudate sepal lobes. Both species have relatively shallow wings at the floral tube, a characteristic feature to discern Burmannia vs. Gymnosiphon. Thus, the author suspects the two new Burmannia spp. as being transitional to the genus Gymnosiphon.
Burmannia coerulea Averyanov