A New and Noteworthy Species of Zanthoxylum (Rutaceae) from the Dry Forests of Peru

A new tree species of Zanthoxylum L. (Rutaceae) from Peru, Z. sanmartinense Reynel., is here described based on morphological characters. It is distributed in a seasonally dry tropical forest in Amazonian Peru, at a low altitude, and belongs to Zanthoxylum sect. Macqueria Comm. ex Triana & Planch., the largest section of the genus; it is unusual in being monoecious, in contrast to the large majority of species, which are dioecious, and in having inflorescences with densely congested, abundant flowers.