Senecio serranus from Parana, Brazil, is described as new. It is related to Senecio dichrous (Bong.) Schultz-Bip., but does not have glandular hairs and does have leaves of the same color on both surfaces. Both species belong to Senecio sect. Dichroa Cabr. and unlike all other ones of the section, have rayless heads with only one type of floret. Among the collections made by Gert Hatschbach in the state of Parana, Brazil, there is an undescribed species of Senecio related to Senecio dichrous (Bong.) Schultz-Bip. but without glandular hairs and with leaves not paler on lower surface than on upper, which is here described. Senecio serranus Zardini, sp. nov. TYPE: Brazil. Parana: Campina Grande do Sul, Serra Capivari Grande, 6 Mar. 1969, Hatschbach 21212 (holotype, MBM; isotypes, MO, US not seen, distributed as Senecio dichrous). Figure 1. Herba erecta; caule striato profunde sulcato glabro ca. 1 m alto. Folia petiolata alterna; lamina glabra oblonga, basi attenuata, apice acuta, margine grosse dentata, nervis reticulatis. Capitula multa discoidea ad apices ramulorum paniculato-corymbosa; involucro campanulato glabro calyculato ca. 9 mm alto ca. 6 mm crasso; bracteolis calyculi 4-6, lanceolatis, 9-13 mm longis; phyllariis 6-8, oblongolinearibus, apice acutis. Flosculi ca. 26, lutei, isomorphi, hermaphroditi; corolla tubulosa ca. 10 mm longa, pentadentata. Achaenia (immatura) costata glabra ca. 6 mm longa; pappo albo capillari ca. 10 mm longo. Erect herb. Stems striate, furrowed, glabrous, 1 m tall. Leaves petiolate, alternate. Blade oblong, attenuate at base, acute at apex, coarsely dentate at margin, with reticulate venation, glabrous or sometimes with evanescent arachnoid tomentum below. Heads many, discoid, in terminal inflorescences paniculate-corymbose. Involucre campanulate, glabrous, 9 mm tall, 6 mm wide, with epicalyx; bracts of the epicalyx 4-6, lanceolate, 9-13 mm long; phyllaries 6-8, linear-oblong, acute. Florets around 26, yellow, isomorphic, hermaphrodite, with tubular corolla 10 mm long, 5-lobed. Achenes (immature) ribbed, glabrous, 6 mm long. Pappus white, capillary, 10 mm long. Paratypes. BRAZIL. PARANA: Campina Grande do Sul, Pico Caratuva, 8 Feb. 1968, Hatschbach 18563 (MBM, MO); Serra Capivari Grande, 18 July 1986, Silva & Zelma s.n. (US not seen, distributed as Senecio dichrous). Senecio serranus Zardini is similar to S. dichrous (Bong.) Schultz-Bip. (basionym, Cacalia dichroa Bong. Brazil. Minas Gerais: Riedel s.n., holotype, LE not seen, photo, MO; see Fig. 2), from which it can be differentiated by the following key. la. Plants without glandular hairs; leaves of the same color on both surfaces ........ S. serranus Ib. Plants with glandular hairs; leaves distinctly paler on lower surface, green above, whitish below S. dichrous These two species belong to Senecio sect. Dichroa, one of the two sections of the genus characterized by a hairy tuft at the apex of the style. The description of this section (Cabrera, 1957) should be amended to include rayless heads with only one type of floret characteristic of both Senecio serranus and S. dichrous. The latter species was treated by Cabrera (1957) within section Dichroa as doubtful because the type of its basionym, Cacalia dichroa Bong., was not seen by him. All the other species of the section have heads with two types of florets, the marginal ones being ligulate. Acknowledgments. I express special gratitude to G. Hatschbach (MBM), to N. Imkhanitskaya of the Komarov Botanical Institute (LE) for help with the study of the type of Cacalia dichroa Bongard, and to A. Cabrera (LP) for reviewing the manuscript.