Many people have expressed frustration at this species to me… that it looks a lot like a few other weedy, pedunculate, purple-flowered species (e.g., R. simplex, R. nudiflora). I find Ruellia tuberosa, the type species of the genus, to be rather distinctive owing to its leaves that are almost always obovate or oblanceolate. Its native range is northern South America.
The second photo depicts a fruiting specimen…long elliptical in shape, preparing to explode (yes, ballistically) and fling its seeds about the environment.
Wild collected, Venezuela, Tripp & Lujan (RSA-POM); Photos by Erin Tripp