Triniochloa talpensis from Mexico is described and illustrated. Its morphology and leaf anatomy are compared with those of T. laxa Hitchcock. RESUMEN. Se describe e ilustra Triniochloa talpensis de Mexico. Se comparan caracteristicas de morfologia y de anatomia foliar con aquellas de T. laxa Hitchcock. Triniochloa is a small genus of grasses that was described by Hitchcock in 1913, the members of which grow in temperate forests from Mexico to Bolivia. It is distinguished from other genera of the Pooideae by its spikelets 1-flowered without a rachilla extension, floret callus obtuse and bearded, and lemma 5or 7-nerved with a bifid apex and geniculate awn inserted above the middle. This genus was included in the tribe Meliceae of the subfamily Pooideae by Reeder (1968) on the basis of its connate leaf sheaths, membranous ligules, truncate lodicules that lack vascular traces, and small chromosomes. He suggested that it is closely related to Schizachne. This placement is supported by Clayton & Renvoize (1986) and Watson & Dallwitz (1992). Triniochloa, as presently circumscribed, includes four species: T. laxa Hitchcock and T. micrantha (Scribner) Hitchcock, which are restricted to Mexico; T. stipoides (H.B.K.) Hitchcock, distributed from central Mexico to Colombia, Venezuela, and Bolivia; and T. andina Luces, known only from Venezuela. The new species from western Mexico increases the number to five. Mature blades of basal leaves from herbarium specimens were used for anatomical studies. A segment about 10 mm long was removed from the middle of the blade, rehydrated by boiling in water, sectioned free-hand, and mounted in glycerin jelly. Epidermis preparations were made following Metcalfe's (1960) method. Drawings were made using an X-100-1 Ken-A-Vision Microprojector. Triniochloa talpensis M. Gonz~lez-Ledesma & M. G6mez-Sanchez, sp. nov. TYPE: Mexico. Jalisco: Municipio de Talpa de Allende, alrededores de la mina Zimap~n en la Sierra de Cuale, ca. 2150 m, 10 Feb. 1992, M. GonzdlezLedesma & J. A. Perez de la Rosa 496 (holotype, CHAPA; isotypes, IBUG, MEXU, MICH, MO, US, XAL). Figure 1. Plantae perennes, rhizomatosae. Culmi 60-110 cm alti. Vaginae foliorum pubescentes prope nodos. Ligulae 1.5-2.5(-5) mm longae. Laminae foliorum planae 2227 cm longae et 3.0-5.0 mm latae inferioribus caducis. Panicula erecta, angusta, 16-34 cm longa, ex vagina exserta. Spiculae 11.0-16.8 mm longae. Glumae inaequales, prima spiculis breviore, 7.5-13.6 mm longa; secunda quam lemma aequanti vel longiore, 11.0-16.5 mm longa. Lemma 11.0-14.5 mm longum, 7-nerve, arista dorsali geniculata, 13.0-23.0 mm longa. Antherae (4.8-) 5.5-7.0 mm longae. Perennial herbs with rhizomes to 20 cm long, 23 mm diam., rhizome sheaths strigose near the nodes. Culms 60-110 cm tall, 1.5-2.0 mm diam. near the base, robust, strongly decumbent, pubescent below the upper nodes. Leaves, at least the lower, ciliate near the collar. Leaf sheath margins connate, the upper sheaths shorter than the internodes and pubescent below. Ligules 1.5-2.5(-5) mm long, membranous. Blades 22-27 cm long, 3.0-5.0 mm wide, flat, deciduous at level of the collar or beneath, adaxial surface scabrous to pubescent, with prominent ribs, abaxial surface glabrous. Panicle 16-34 cm long, 1.0-2.0(-2.5) cm wide, erect, narrow, completely exserted, with 30-65(-90) spikelets; panicle axis glabrous below, scabrous on the angles toward the apex; lowest node 1-2-branched; branches appressed or ascending, scabrous at least toward the apex. Spikelets 11.0-16.8 mm long, 1-flowered. Glumes unequal, hyaline except near the nerves. First glume 7.5-13.6 mm long, shorter than the spikelet, 1-nerved. Second glume 11.0-16.5 mm long, as long as the spikelet, 3-nerved. Lemma 11.0NovoN 5: 36-39. 1995. This content downloaded from 157.55.39.211 on Fri, 24 Jun 2016 06:28:38 UTC All use subject to http://about.jstor.org/terms