Monocostus is a genus with only one described species, and that species is endemic to one small area of northern Peru in Department San Martin near the city of Tarapoto. I went there in 2008 to try to find this plant in habitat but with no luck. Most of the area where it was found has now been cleared of forests, and although it is not on an official endangered list, I am sure that there are few if any plants left in the wild. Fortunately this beautiful little plant is widely cultivated and therefore not yet totally lost to humanity.
The genus (and species) is distinguished by having non-rhizomatous, ribbed roots. The stems are erect from the root system, sprirally contorted, formed by sheathing leaf bases which are unbranched. The flowers are solitary (thus the epiphet "uniflorus" for the species) and are borne from the leaf axils like Paracostus.
SHOWN IN PHOTO: Monocostus uniflorus