356 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
107. PHRAGMITES Trin. Fund. Agrost. 134. 1820. 
1. Phragmites phragmites (L.) Karst. Deutsch. Fl. 378. 1883. REED. 
Arundo phragmites L. Sp. Pl. 81. 1753. 
Type locality, ‘‘in Europese lacubus fluviis.’’ 
Rance: Throughout the temperate regions of the world. 
HERBARIUM SPECIMENS FROM Mexico: 
Lower CaLiForNIA: Santa Agueda, Palmer 211 in 1890. Wild Island, McGee 
in 1896. 
Cotmma: Manzanillo, Palmer 1092 in 1890, 
Tasasco: San Juan Bautista, Rovirosa 651. 
108. TRIDENS Roem. & Schult. Syst. Veg. 2: 34, 599. 1817. 
KEY TO THE SPECIES, 
Panicle included in fascicles of leaves; low plants with stolons... 7. 7. pulchellue. 
Panicle exserted; plants not stoloniferous (except nos. 5 and 6). 
Panicle open, the branches spreading, the spikelets scattered. 
Lemmas 2 mm. long; panicles 3 cm. or more long; spike- 
lets not over 5 mm. long..................-.-.---- 3. T. eragrostoides. 
Lemmas 4 mm. long; panicle rarely over 12 cm. long i spike 
lets about 8 mm, long.......... - 4. T. texanus. 
Panicle contracted or sometimes spike-like; . spikelets 1 crow wded. 
Panicle long and narrow; lemmas awnless. 
Lemmas glabrous; spikelets 5 to 6 mm. long; blades 
flat... ee cee eee 1. T. albescens. 
Lemmas pilose; spikelets about 8 mm. long: blades 
involute..........-...-2.-2222222- 22-22 ee eee 2. T. muticus. 
Panicle short, oval; lemmas awned, very pilose. 
Lemmas acuminate, the awn from a slightly notched 
0 6. T. pilosus. 
Lemmas truncate, the awn from between two rounded 
lobes... 2.2222. eee eee 5. T. avenaceus, 
1. Tridens albescens (Munro) Woot. & Standl., N. Mex. Agric. Sta. Bull. 81: 129. 
1912, 
Tricuspis albescens Munro; Gray, Proc. Acad. Phila. 1862: 335. 1863, nomen nudum. 
Triodia albescens Vasey, U. 8. Dept. Agr. Div. Bot. Bull. 122: pl. 33. 1891. 
Type locality, Texas. 
RaneeE: Kansas and Louisiana to Arizona and Coahuila. 
HERBARIUM SPECIMEN FROM MEXICO: 
CoanuILa: Rfo Grande Valley near Diaz, Pringle 9023. 
2. Tridens muticus (Torr.) Nash in Small, Fl. Southeast. U. S. 142. 1903. 
Tricuspis mutica Torr. U. S. Rep. Expl. Miss. Pacif. 4: 156. 1856. 
Type locality, ‘‘Laguna Colorado, New Mexico.’’ 
Rance: Southwestern United States and northern Mexico. 
HERBARIUM SPECIMENS FROM Mexico: 
Sonora: Nogales to Cocospora.Ranch, Griffiths 6831. Loquka Ranch to Altar, 
Griffiths 6907. 
CHIHUAHUA: Santa Eulalia Mountains, dry calcareous soil, Pringle 405. 
Durangao: Tlahualilo, barren hills, Pittier 468. 
3. Tridens eragrostoides (Vasey & Scribn.) Nash in Small, Fl. Southeast. U.S. 
142, 1903. 
Triodia eragrostoides Vasey & Scribn. Contr. U. 8S. Nat. Herb. 1: 58. 1890. 
