New species of Lessingianthus ( Asteraceae , Vernonieae ) from Brazil and Paraguay

Two new species of the genus Lessingianthus (Vernonieae, Asteraceae) from Brazil and Paraguay are described and illustrated. Lessingianthus cipoensis is characterized by the presence of solitary heads disposed in short branches and ovate to elliptical leaves. It has a certain resemblance to L. vestitus, which has more branched inflorescences, with long branches, and lanceolate to obovate-lanceolate leaves. Lessingianthus paraguariensis is closely related to L. asteriflorus and L. mollissimus, but it can be distinguished by the broadly elliptical leaves and the large size of the outer phyllaries.

Lessingianthus can be distinguished from the remaining American members of the tribe by its non-glandular anther appendages, lack of basal style node and quadrate raphids in the achene wall (Robinson 1999).The genus is distinguished also by the surface morphology of the pollen grains and the basic chromosome number.The pollen grains have been called type "B" by Keeley & Jones (1979) and they are tricolporate, echinolophate, with a discontinuous tectum, germinal furrows very long, converging at poles and lacunae disposed in a regular pattern, lacking a polar lacuna (Angulo & Dematteis 2010).The basic chromosome number of the genus is x = 16, differing from the majority of the American Vernonieae with a base of x = 17 (Dematteis 2002).
Following the segregation of Lessingianthus (Robinson 1988), the only modification has been the transference of Lessingianthus subgen.Oligocephalus H.Rob. to the genus Chrysolaena H.Rob. (Dematteis 2007).In addition, several species still included in Vernonia have been transferred and new ones were described (Díaz-Piedrahita & Obando 2002, Dematteis 2006, 2008, Dematteis & Angulo 2010).In the present paper two new species of Lessingianthus from Brazil and Paraguay are described and illustrated.

MATERIALS AND METHODS
Pollen samples were obtained by removing one or two florets from herbarium specimens of the species.The pollen grains were acetolysed according to the procedure suggested by Erdtman (1966).For light microscopy (LM) the pollen samples were mounted in glycerine-jelly on glass slides and then examined with a Zeiss Axioplan microscope.Permanent slides were deposited at the Palynological Laboratory of the Universidad Nacional del Nordeste (PAL-CTES).For scanning electron microscopy (SEM), acetolysed pollen grains were first washed in 96 %, and then 100 % alcohol, next sputtered with goldpalladium and then observed in a JEOL 5800 LV scanning electron microscope.The terminology applied for pollen grain description in general follows Erdtman (1966) and Punt et al. (2007).
Leaves alternate, sessile, coriaceous, discolour, the greatest 6-8 by 3-4 cm, placed on the middle portion of the stem.Leaf blades broadly elliptic, entire, acute at the apex, obtuse at the base, glabrous or scarcely lanate above, white-tomentose beneath, pinnatinervate, secondary veins 10-15, scarcely curved.Bracts of the inflorescence absent.Etymology -The specific epithet refers to the region where the species occur.
Note -Lessingianthus paraguariensis is closely related to L. asteriflorus (Mart.ex DC.) H.Rob. and L. mollissimus (D.Don) H.Rob., but it can be distinguished by the broadly elliptical leaves and the size of the outer phyllaries, larger than the inner ones.Lessingianthus asteriflorus and L. mollissimus have lanceolate to oblong-lanceolate leaves and outer phyllaries shorter than the inner ones.In addition, the new species has the larger leaves in the middle portion of the stem, while L. asteriflorus and L. mollissimus have the larger leaves at the base of the stems.
In campo and on grassy savannas with dry, rocky soils.Flowering and fruiting in January and March.