Two New Species of Paspalum (Poaceae: Paniceae) from Venezuela and Colombia

Abstract

Morphological characters support the description of two new species of Paspalum: P. atabapense, from Depto. Atabapo, Venezuela, in group Alterniflora; and P. tillettii, from Comisaria del Guainia, Colombia, and Territorio Federal Amazonas, Venezuela, in an unspecified taxonomic group but clearly related to P. schultesii Swallen. Preparatory to completing an account of the genus Paspalum for the Flora of the Venezuelan Guayana, two new species are described and illustrated. Paspalum L., with more than 350 species, is one of the largest genera of grasses. It is confined primarily to the New World, although a few species occur in Africa, Asia, and Oceania. Several species are pantropical or nearly so, and two weedy species have now become widely naturalized as weeds in the tropics. A few have been widely distributed as forage grasses and have subsequently become naturalized in new areas. The most useful taxonomic treatment of this genus remains the monograph of the North American species (including Mesoamerica) by Chase (1929). Paspalum atabapense Davidse & Zuloaga, sp. nov. TYPE: Venezuela. Amazonas: Depto. Atabapo, SE bank of the middle part of Caio Yagua at Cucurital de Yagua, 3036'N, 66?34'W, 120 m, 8 May 1979, G. Davidse, 0. Huber & S. S. Tillett 17414 (holotype, MO; isotypes, IAN, SI, US, VEN). Figure 1. Gramen perenne caespitosum; culmi 45-75 cm alti. Folia basalia; ligulae 0.5-1.2 mm longae, glabrae; laminae 6-18.5 cm x 0.3-0.4 mm, filiformes. Racemus 1, 39.5 cm longus; rhachis 0.4-0.5 mm lata, exalata vel interdum anguste alata basin versus. Spiculae 2.6-3.6 x 1.0-1.3 mm, ellipticae anguste, singulares, pubescentes; gluma inferna absens; gluma supera 0.3-0.7 mm spicula brevior. Flosculus superus 2.6-3.5 x 1.0-1.3 mm, stramineus. Antherae 1.5-1.9 mm longae. Caespitose, perennial herbs. Culms 45-75 cm long, erect, unbranched above the base, with 2-3 nodes above the base; internodes cylindric, glabrous; nodes dark, glabrous or pilose. Leaves basal. Sheaths striate, rounded, densely pilose toward the base with appressed, whitish hairs, to sparsely pilose toward the apex, the margins glabrous. Ligules 0.5-1.2 mm long, membranous, glabrous, erose. Blades 6-18.5 cm long, 0.3-0.4 mm wide, filiform, involute, the adaxial surface scabrous, prominently ridged, the abaxial surface glabrous, the apex permanently involute, somewhat pungent. Inflorescences terminal, long-exserted; peduncle 4-17 cm long, cylindric, glabrous; raceme 1, 3.0-9.5 cm long, slightly arching, densely pilose at its base; rachis 0.4-0.5 mm wide, puberulent to glabrous, concavo-convex, unwinged or sometimes with partially developed wings 0.1-0.2 mm wide near a portion of the base, terminating in a spikelet; pedicels 0.1-0.3 mm long, densely short-pilose. Spikelets 2.6-3.6 mm long, 1.0-1.3 mm wide, solitary, plano-convex, narrowly elliptic, pilose. Lower glume always absent. Upper glume 2.4-3.0 mm long, 0.3-0.7 mm shorter than the upper floret, acute, 3-nerved. Lower floret sterile. Lower lemma as long as the spikelet, 3-nerved, glabrous to puberulent in the middle portion, pilose toward the margins. Lower palea usually absent, rarely developed and then to 5/6 as long as the lower lemma. Upper floret 2.6-3.5 mm long, 1.0-1.3 mm wide, as long as the spikelet, bisexual, narrowly elliptic, stramineous, chartaceous, smooth, papillose, the papillae regularly distributed; lemma 3-nerved, short-pilose, with prickle hairs at the apex. Stamens 3; anthers 1.5-1.9 mm long, purple. Styles 2, separate; stigmas about as long as the styles, plumose. Caryopsis (1.2-)1.4-1.5 mm long, 0.9-1.0 mm wide, obovate in outline; hilum punctiform; embryo ca. 2/5 as long as the caryopsis. Paratypes. VENEZUELA. AMAZONAS: Depto. Atabapo, area between the W base of Cerro Yapacana and the headwaters of Caio Cotua, 3?38'N, 66?52'W, 6 May 1979, Davidse, Huber & Tillett 17251 (K, MO, SI, US, VEN); Depto. Atabapo, sabanas y bosques ribereios en los alrededores de Canarip6, en la margen izquierda (Sur) del bajo Rio Ventuari, a unos 20 km al E de la confluencia NOVON 2: 193-197. 1992. This content downloaded from 157.55.39.209 on Sat, 14 May 2016 04:53:24 UTC All use subject to http://about.jstor.org/terms