The Dendrobium nugentii is on the right and in bloom. Dendrobium linguiforme is on the left and has never bloomed. These species are very similar and were, or maybe still are, considered varieties instead of separate species. Both have thick, roughly textured leaves and both have longitudinal creases in the leaves although they are more distinct on the linguiforme. The nugentii texture is almost like a cat tongue but the linguiforme is more like 400 grit sandpaper. For a post showing the flowers of the D. nugentii go here.