A new species of Poaceae, Paspalum volcanensis, from southern Bolivia and northwestern Argentina, is described and illustrated. Its concavoconvex spikelets and upper lemma with conspicuous nerves are characters it shares with other species of subgenus Anachyris of Paspalum. A key to the species of the subgenus and comments on the delimitation of the new species are provided here. In preparation of a treatment of the genus Paspalum L. for Flora Neotropica, examination of recent collections from Bolivia and Argentina has revealed a new species within subgenus Anachyris (Nees) Chase. Paspalum volcanensis belongs to subgenus Anachyris (Nees) Chase, due to the presence of concavo-convex spikelets, and upper lemmas with conspicuous nerves on the abaxial surface. Within this subgenus, this new species is related to P usterii Hackel: spikelets are pilose in both species, and the upper glume is always present. It differs from R usterii by height, and inflorescence and spikelet size; the latter species grows in southern Brazil, eastern Paraguay, and northeastern Argentina, between 0 and 1200 m elevation, while R volcanensis is present in southern Bolivia and northwestern Argentina, between 1000 and 2300 m elevation. Paspalum volcanensis Zuloaga, Morrone & Denham, sp. nov. TYPE. Argentina. Jujuy: Dpto. Tumbaya, Volcan, cantera al SE del pueblo, 2100-2200 m s.m., 13 Feb. 1985, R. Kiesling, S. Botta, C. Ezcurra, M. Sanchez & E. Ulibarri 5170 (holotype, SI; isotypes, MO, US). Figures 1A-C, 2. Culmi erecti, 45-60 cm alti. Laminae foliares lanceolatae, 12-22 cm longae, 0.7-1.3 cm latae. Racemi 4-19, adscendentes vel patentes, infimi 4-9 cm longi; spiculis ellipsoideis, 2.5-3 mm longis, 1.1-1.2 mm latis; gluma superiore 3-nervi; lemmate inferiore 3-nervi, palea inferiore absente; anthoecio superiore ellipsoideo; lemmate fertili valde 7-nervi. Caespitose perennials, with extravaginal innovations and short rhizomes covered by glabrous cataphylls. Floriferous culms 45-60 cm tall, 2.4-3 mm diam.; nodes 2-3, brownish, glabrous or sparsely pilose; internodes 2.5-15 cm long, glabrous, striate, stramineous. Sheaths longer or shorter than the internodes, 9.5-22 cm long, striate, slightly compressed and keeled toward the distal portion, glabrous, one margin hirsute, the other glabrous or hirsute toward the distal portion. Ligules membranous, 2-3.5 mm long, pale brown, glabrous; pseudoligule a ring of whitish hairs up to 6 mm long. Blades lanceolate, 12-22 cm long, 0.7-1.3 cm wide, flat, ascendent, slightly divergent from the culm, rounded at the base, the apex acuminate, glabrous on both surfaces or the abaxial surface papillose-pilose, the margins papillose-pilose. Peduncles 9-25 cm long, terete, glabrous. Inflorescences terminal, exserted, 9-17 cm long, 4-9 cm wide; main axes 6-10 cm long, glabrous, ending in a naked point; racemes 4-19, ending in a spikelet, alternate to subopposite, divergent from the main axes, the lower ones 4-9 cm long; pulvini covered by whitish hairs, up to 0.5 mm long; rachises 11.6 mm wide, glabrous, brownish or purplish, the margins papillose-pilose; spikelets imbricate, distributed in 4 series; pedicels subterete, paired, glabrous, unequal, the upper ones 0.5-1.3 mm long, the lower ones half as long as the upper ones. Spikelets ellipsoid, 2.5-3 mm long, 1.1-1.2 mm wide, concavo-convex, pilose, pale and tinged with purple. Lower glumes absent. Upper glumes ? to equal the spikelet length, acuminate, membranous, dorsal surface sparsely pilose, with adpressed hairs more densely disposed toward the base, margins papillose-pilose, 3-nerved, the nerves conspicuous, one central and two submarginal. Lower lemmas equal to the upper anthoecium or slightly longer, membranous, glabrous, hyaline, 3-nerved, the nerves conspicuous, depressed at base. Lower paleas absent. Upper anthoecia concavo-convex, as long as the spikelets, indurated, glabrous, finely papillose. Upper lemmas 7-nerved, the midvein and lateral veins conspicuous. Upper paleas indurated, 2-nerved; lodicules 2, ca. 0.3 mm long, conduplicate, hyaline; stamens 3, the anthers 1.6-2.2 mm NovoN 10: 183-186. 2000. This content downloaded from 157.55.39.138 on Thu, 19 May 2016 06:27:36 UTC All use subject to http://about.jstor.org/terms