Abstract
We describe and illustrate Aristolochia assisii, a new species assigned to subseries Anthocaulicae. This subseries is characterized by the presence of extremely short and ramiflorous racemes in which each flower is subtended by a small bract. The inflorescences and the flowers of the new species are morphologically similar to those found in three woody climbers of this subseries (A. bahiensis, A. disticha and A. subglobosa); however, it clearly differs by the herbaceous condition, a trait extremely rare in cauliflorous species that suggests neoteny, and the possession of a long, cylindrical rhizome and a tapered rostrum to 1.2 cm long in the capsule. So far, A. assisii is the third species of the subseries Anthocaulicae known to occur in the Atlantic Forest of Brazil.