5.25.Begonia juntasensis Kuntze, Revis. Gen. Pl. 3(3): 106 (1898). – Type: Bolivia, [La Paz Department], río Juntas, [16°57′S, 65°47′W], 800 m, 13–21 vi 1892, C.E.O. Kuntze s.n. (lectotype NY [NY00118621] designated here, first stage designated in: Revista Univ. (Cuzco) 33(87): 82 (1944) by Smith, L.B. & Schubert, B.G.; isolectotype NY [NY01085499]). L.B. Smith & B.G. Schubert, Revista Univ. (Cuzco) 33(87): 82 (1944); R.C. Foster, Contr. Gray Herb. 184: 137 (1958); D.C. Wasshausen et al. in P.M. JØrgensen et al. (eds), Cat. Bolivia, Monogr. Syst. Bot. Missouri Bot. Gard. 129: 385 (2013).

Begonia cuninghamei Sprague, Bull. Misc. Inform. Kew 1912(7): 340 (1912). – Type: Cultivated in the Royal Botanic Gardens Kew, 14 vii 1912, H.C. Baker 437-11 (lectotype K [K000739941] designated here, isolectotype K [K000739940]), syn. nov.

L.B. Smith & B.G. Schubert, Revista Univ. (Cuzco) 33(87): 80 (1944); R.C. Foster, Contr. Gray Herb. 184: 137 (1958).

Begonia subrectangula Rusby, Phytologia 1: 67 (1934). – Type: Bolivia, [La Paz Department], Nequejahuira, [16°20′S, 67°50′W], 8000 ft, 15–24 v 1926, G.H.H. Tate 656 (lectotype NY [NY00118702] designated here).

R.C. Foster, Contr. Gray Herb. 184: 138 (1958).

Begonia denticulata auct. non. Kunth, Rusby, Bull. Torrey Bot. Club 3: 40 (1893); Wasshausen et al. in P.M. JØrgensen et al. (eds), Cat. Bolivia, Monogr. Syst. Bot. Missouri Bot. Gard. 129: 384 (2013).

Begonia sanguinea auct. non. Raddi, Rusby, Bull. New York Bot. Gard. 4: 312 (1907).

Begonia bracteosa auct. non. A.DC., Wasshausen et al. in P.M. JØrgensen et al. (eds), Cat. Bolivia, Monogr. Syst. Bot. Missouri Bot. Gard. 129: 384 (2013) pro parte.

Distribution. Endemic to Bolivia.

Nomenclatural notes. The protologue of Begonia juntasensis Kuntze (1898: 106) cites material collected by Kuntze at 800 m elevation along the río Juntas. Smith & Schubert (1944a) cited matching material in New York herbarium as the type, which counts as an effective first-stage lectotypification. There are two such sheets in the New York Botanical Garden herbarium, and we designate the sheet NY00118621 as the lectotype. This sheet has a determination slip that indicates Smith and Schubert considered it the type of Begonia juntasensis, despite an earlier slip indicating that the sheet is a co-type. We designate the only known sheet of G.H.H. Tate 656 in the New York Botanical Garden herbarium (NY00118702) as the lectotype of Begonia subrectangula Rusby.

The protologue of Begonia cuninghamei Sprague cites living material grown from seed received from H. C. Baker in 1911 (Sprague, 1912). The seeds were originally collected by L. Cuninghame, for whom the species was named. There are two sheets of H. C. Baker 437- 11 in Kew herbarium. These were collected on 4 July 1912, which is before the protologue was published on 30 September 1912. These sheets are determined as this species and can be considered as original material of this name. We designate the sheet K000739941 as the lectotype, because it includes fruits, staminate material, and pistillate material.

Synonymy notes. Begonia cuninghamei was tentatively synonymised with B. bridgesii by Smith & Schubert (1944a), who had not seen type material of either species, based on the descriptions in the protologues. The types of Begonia cuninghamei differ from those of B. bridgesii in several respects, including the persistent stipules (vs deciduous), the transversely obovate leaves (vs ovate), and the rounded (vs straight-sided) fruits. These characters are all shared with the type of Begonia juntasensis, so we transfer B. cuninghamei into synonymy with B. juntasensis.

Begonia denticulata Kunth is a common species from Colombia and Venezuela that superficially resembles several Bolivian species of Begonia sect. Hydristyles. This name was first cited in Bolivia by Rusby (1893), based on the collection M. Bang 333, and later by Wasshausen et al. (2013), who cited T.B. Croat et al. 84780. Both collections fall within our concept of Begonia juntasensis, so we include both citations as misapplied names. The specimen M. Bang 333 was also erroneously identified by Rusby (1907) as Begonia sanguinea Raddi, which is a distantly related species endemic to Brazil.

Identification notes. Begonia juntasensis is one of two members of Begonia sect. Hydristyles with persistent stipules and transversely ovate leaves. It differs from the other (B. santarosensis Kuntze) in its entire to serrulate leaf margins (vs serrate) and its white to pink tepals (vs red).