A New Species of Rytigynia (Rubiaceae, Vanguerieae) from Northeastern Tanzania, with Notes on the Circumscription of the Genus

摘要

We discuss the history and circumscription of the genus Rytigynia (Rubiaceae, Vanguerieae) and present the morphological characters used for the delimitation of the genus in a new, restricted sense. We describe Rytigynia dichasialis, a new species from northeastern Tanzania that is unique in the genus by having long-pedunculate and dichasially cymose inflorescences with well-developed secondary axes. We compare the new species to other, morphologically similar species of Rytigynia and present the characters used to distinguish among them.