Thanks to a new friend and colleague who is studying Acanths of Junín, Peru–Rosa María Villanueva Espinoza–I have finally laid eyes on flowering material of Ruellia tarapotana after all these years of not really having a clear idea of what this species look like.
One can, after all, conjure all kinds of 3-dimensional forms for a species based on herbarium material, but unless you are Bobbie Angell or Alice Tangerini, one usually fails at this sort of approximation.
In the protologue, Lindau (1904) describes this species as having glabrous leaves 12-18 cm long, violet flowers arranged in an apical manner forming a spike-head like inflorescence, and corolla tubes ca. 40 mm long. It fits!
Fairly confident I have seen and collected sterile material of R. tarapotana in the wild (near Aguaytía, Peru), but this is my first sighting of it with flowers, so huge thanks to Rosa for kindly sharing her report!
This species is phylogenetically most likely closely related to a group of wet, lowland Amazonian species including R. cuyabensis, R. lasiostachya, and R. terminale. Just a guess. Wait for it.
Wild Collected, La Génova Farm, 1161 m, Rosa María Villanueva #160, Photos by R. Villanueva.