This study was based on morphological analyses from both herbaria and field material. Nine species were recorded, distinguished from each other mainly by the root system, phyllotaxis, leaf type, color of the flowers and inflorescence and capsule morphology. Of these species, two (Oxalis corniculata L. and O. cratensis Oliver ex Hooker) showed preferential distribution from the Litoral and Forest zones to the Agreste subzone. Oxalis psoraleoides Kunth is widely distributed over the entire state. Oxalis triangularis A. St.-Hil. and O. frutescens L. are distributed from the Littoral and Forest zones to the Sertão subzone. Oxalis divaricata Mart. ex Zucc. is distributed in the Agreste and Forest subzones, occurring also at Fernando de Noronha Archipelago. Oxalis hedysarifolia Raddi occurs in the Forest zone and in the Agreste subzone, where it is restrict to the mountains. Oxalis debilis Kunth is restricted to the Agreste zone, and Oxalis glaucescens Norlind is the only one found exclusively in sandy caatingas, in the Sertão subzone. Identification keys, comments on the affinities and geographic distribution, as well as illustrations, are presented.
Oxalis; Oxalidaceae; taxonomy; Pernambuco State; Brazil
