WOOTON AND STANDLEY FLORA OF NEW MEXICO. 91 



58. TRIDENS Roem. & Schult. 



Perennials with flat or involute leaves and open or contracted, sometimes spike- 

 like inflorescence; spikelets 3 to many-flowered, the flowers perfect or the upper 

 staminate; glumes keeled, obtuse to acuminate, usually shorter than the lemma; 

 lemmas 3-nerved, the midnerve or all the nerves exciu-rent, pilose, the apex entire 

 or shortly 2-toothed; i)alea compressed, 2-keeled; stamens 3; styles short, distinct. 



KEY TO THE SPECIES. 



Lemmas not pilose on the back; glumes considerably surpassing 

 the lower florets; spikelets subcompressed, oblong, in a 



rather dense spikelike panicle 1 . T. albescens. 



Lemmas pilose on the back, at least at the base; glumes barely as 

 long as the lowest florets, or shorter; spikelets various. 

 Spikelets terete; sterile lemma not ciliate; neither lobed nor 



awned 2. T. mutdcus. 



Spikelets compressed; sterile lemma ciliate, deeply bilobate, 

 with an intermediate awn. 

 Lemmas only slightly cleft at the apex, the lobes narrow, 



acute; spikelets 10 mm. long 3. T. avenaceus. 



Lemmas cleft half their length, the lobes obtuse; spike- 

 lets 6 to 8 mm. long 4. T. nealleyi. 



1. Tridens albescens (Vasey) AVoot. & Standi. N. Mex. Agr. Exp. Sta. Bull. 81: 



129. 1912. 

 Triodia albescens Vasey, U. S. Dept. Agr. Div. Agrost. Bull. 12^: 33. 1891. 

 Sieglingia albescens Kuntze; L. H. Dewey, Contr. U. S. Nat. Herb. 2: 538. 1894. 

 Rhombolytrum albescens Nash in Britton, Man. 129. 1901. 

 Type locality: "Texas and New Mexico." 

 Range: Kansas to Texas and eastern New Mexico. 



New Mexico: Mesilla Valley; Carlsbad; Roswell. Dry plains, in the Lower and 

 LTpper Sonoran zones. 



2. Tridens muticus (Torr.) Nash in Small, Fl. Southeast. U. S. 143. 1903. 

 Tricuspis mutica Torr. U. S. Rep. Expl. Miss. Pacif. 4: 156. 1856. 

 Triodia mutica Benth.; S. Wats. Proc. Amer. Acad. 18: 180. 1883. 

 Type locality: liagima Colorado, New Mexico. 



Range: Western Texas and eastern New Mexico. 



New Mexico: Socorro; Laguna Colorado; Cross L Ranch; Tortugas Mountain; 

 Roswell. Dry hills, in the Lower and Upper Sonoran zones. 



3. Tridens avenaceus (H. B. K.) Hitchc. Contr. U. S. Nat. Herb. 17: 357. 1913. 

 Triodia avenacea H. B. K. Nov. Gen. & Sp. 1: 156. pi. 48. 1816. 



Triodia grandiflora Vasey, Contr. U. S. Nat. Herb. 1: 59. 1890. 

 • Sieglingia avenacea grandiflora L. H. Dewey, Contr. U. S. Nat. Herb. 2: 538. 1894. 



Tridens grandiflorus Woot. & Standi. N. Mex. Agr. Exp. Sta. Bull. 81: 129. 

 1912. 



Type locality: "Incouvalle Mexicana inter montem Chapultepec et Penol de 

 los Banos." 



Range: Western Texas to Arizona and southward. 



New Mexico: Kingston ( i/eto///e 1334) . 



4. Tridens nealleyi (Vasey) Woot. & Standi. N. Mex. Agr. Exp. Sta. Bull. 81: 



129. 1912. 

 Triodia nealleyi Vasey, Bull. Torrey Club 15: 49. 1888. 

 Sieglingia nealleyi L. H. Dewey, Contr. U. S. Nat. Herb. 2: 538. 1894. 

 Type locality: Western Tey as. 



