A taxonomical study of the Chilean Stevia is herein presented since there is no agreement on current names and the number of species for Chile. A detailed morphological analysis of type and non-type specimens including new field observations was undertaken. In this work we recognized only one species of Stevia in Chile: S. philippiana. This species has a wide morphological variation mainly in leaf and pappus features. A lectotype of the name S. hyssopifolia was designated. Stevia hyssopifolia var. panulensis was regarded as a new synonym of S. philippiana. On the other hand, S. adenophora and S. chamaedrys were excluded from the Chilean flora. Finally, Porophyllym tarapacanum was excluded from the Tagetean genus Porophyllum and included as a new synonym of S. philippiana, too.

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Stevia Cav. (Asteraceae, Eupatorieae) includes ca. 235 species distributed from United States of America to Chile and Argentina in South America. During the taxonomic revision of the Argentinian species several specimens belonging to Stevia mandonii Sch. Bip. were found in the province of Jujuy, where it had not been previously cited. In this framework, the goals of the present article are 1) to report the species in Argentina for the first time, 2) to differentiate it among morphologically close species, and 3) to perform a taxonomical analysis based on herbarium specimens, populations in the field, bibliography and type material. Morphology was analyzed by means of optical microscopy and scanning electron microscopy techniques. Stevia mandonii is readily distinguished by its small size of 10-20 cm, rounded leaves and pappus formed by 9-17 bristles with presence of heterocarpy. A detailed morphological description, an illustration, a geographic distribution map, and a key to species of Stevia that occur in Jujuy are provided. The designation of a lectotype for the name Stevia mandonii is properly discussed.

A revision and a morphological analysis of the Uruguayan species of Stevia (Compositae, Eupatorieae) were performed. Leaf, inflorescence, pubescence and pappus traits were identified as key to separate species. Stevia entreriensis, S. entreriensis var. minor, and Dissothrix hassleriana were considered synonyms of S. hirsuta, and S. ophryodonta and S. oxylaena synonyms of S. veronicae. Lectotypes for the names Stevia cinerascens, S. megapotamica, S. linariifolia, S. selloi, S. selloi var. yparacayensis, S. oxylaena and S. veronicae were designated. Stevia burkartii was excluded from the Uruguayan flora. As a result, 10 Uruguayan species are considered: S. aristata, S. cinerascens, S. congesta, S. gratioloides, S. hirsuta, S. multiaristata, S. sabulonis, S. satureiifolia, S. selloi, and S. veronicae. A key to the Uruguayan species, descriptions, photographs and distribution maps are provided.

Eleven species of Stevia were reported from Uruguay: S. aristata, S. burkartii, S. cinerascens, S. congesta, S. entreriensis, S. gratioloides, S. multiaristata, S. ophryodonta, S. sabulonis, S. satureiifolia, and S. selloi. Seven are shared with Argentina, five with Brazil, four with Paraguay, and two are endemic to Uruguay. During the revision of these species of Stevia, we detected names which need lectotypifications. As a result of our analysis four lectotypes are designated for names currently accepted in Stevia: S. congesta, S. gratioloides, S. polycephala (= Stevia aristata) and Dissothrix hassleriana (= Stevia entreriensis). We also clarified the original localities of type materials of S. congesta which occurs in Uruguay and, probably, in Brazil.

Stevia diversipapposa was first described by Hieronymus in 1897, along with its forms breviaristata, exaristata and longiaristata. All these names are considered as later synonyms of S. vaga, a widespread shrub from northwestern and central Argentina, described by Grisebach in 1874. During our revision of the Argentinian species of Stevia, we found that type designations were missing for S. diversipapposa and its forms breviaristata and exaristata. Three specimens of CORD herbarium are chosen here as the lectotype of S. diversipapposa, and the neotypes of S. diversipapposa f. breviaristata and S. diversipapposa f. exaristata. Additionally, we provide a re-description of the species and a distribution map of S. vaga.