Both my Promenaea species were in bloom recently, this and the species shown in the previous post. That species is more beautiful, this more interesting, in my opinion. Like the other, this is from Brazil and has a similar growth habit, so much so that it would be difficult to tell them apart when they are not blooming.
The plant is 10-12 cm and the flowers are 5 cm and are produced singly or in pairs on semi-pendant stems about 5 cm long. For that reason the plant is best grown in a small basket or a net pot. I grow mine in a net pot in live sphagnum moss and give it rather low light and cool conditions with good air movement.
The species name of this plant, stapelioides, was given on account of the flowers' resemblance to the flowers of the genus of succulents, Stapelia, with their fleshy star-shaped flowers. The purple, almost black color of these flowers is especially reminiscent of those succulent flowers.