The subtribe represents a diverse assemblage native to tropical South America and a contiguous portion of Central America.[1] Not only is this subtribe remarkable for the range of morphological and ecological variation within it, but it also includes species that represent novel exceptions to the terrestrial habit, longitudinally-dehiscent anthers, and/or exarillate seeds typical of the family. Exceptional taxa include Dichorisandra, characterized by the unusual combination of a vining habit, poricidal anthers, and arillate seeds. Cochliostema is atypical in having an epiphytic habit and flowers with spirally-coiled anthers concealed in petaloid extensions of the filament. Geogenanthus is distinguished by a particular 6-celled stomatal complex and basal axillary inflorescences. Plowmanianthus consists of prostrate herbs shallowly rooted in the leaf-litter layer of rainforest floors, and the flowers of most Plowmanianthus species are primarily cleistogamous.[2]
Faden & Hunt's (1991) formal circumscription of the subtribe[1] did not include Plowmanianthus, which was then undescribed and poorly understood; Hardy & Faden added Plowmanianthus in 2004.[2] Members are perennial, primarily understory, herbaceous taxa united on the basis of chromosome morphology (generally large), a shared base chromosome number (x = 19), and a biseriate arrangement of seeds in each locule (two longitudinal files of seeds in each locule), although the seeds are uniseriate in Plowmanianthus.[2]
