Monophyllaea singularis growing at the mouth of Fairy Cave in Sarawak. Unlike the previous species, this is a large plant, the single oblong leaf reaching 90cm long. Another peculiar feature of this species is that the flowers grow as double rank along the leaf stalk, and may spread to the upper surface of leaf lamina down the mid-rib - you can roughly make out the undulations on the leaf stalk at the top photo, these are the flowers. Unfortunately I could not get a good closeup due to the fading light.
While locally common, throughout the world, this plant is only found in the limestones around the Bau area in Sarawak.