Nepenthes robcantleyi is a beautiful highland Phillipine species from the southeast Mindanao Cordillera. The species has huge pitchers and exhibits a deep purple coloration that approaches black in some specimens. The species seems to have such a strong preference for epiphytic habitats that it's been difficult to observe in many wild populations because it resides so high in the treeline.
The genesis of Nepenthes robcantleyi and nebularum has been enshrouded in controversy for decades. Among leading Nepenthes scientists who have observed plants of robcantleyi/nebularum in the wild, the overwhelming consensus is that Nepenthes robcantleyi includes nebularum. Further genetic, field and statistical work may afford for their split but this is unlikely and a number of publications are pending that address the issue. The fundamental idea behind these publications is that the variation in the proposed nebularum in nature is very broad, and the arguments made for the split are based on a narrow set of cultivated material for both robcantleyi/nebularum. In-situ observation reveals that there is some minor variance at the northern and southern ends of the robcantleyi/nebularum distribution along the (very long) mountain range in question. However, they all fall under the umbrella of the originally described species robcantleyi.