18 . 



Oil lava Ijeds, T'edrigal, Valley of Mexico, Federal District, 6579 C. G. Pringle, 

 Octol)er 2, 1896. 



Aristida longiramea Presl, Rel. Haeiik. 1: 284 (1830). 



Las Sedas, State of Oaxaca, 918 (in part) C. L. Smith, September, 1894. 



Aristida purpurea Nutt. Trans. Am. Phil. Soc. 5: 14.5 (1837). 



Saltillo, State of Coahuila, 392 E. Palmer, September, 1898. A very slender form, 

 growing among rocks on hillsides. 



Aristida scabra Kunth, Kev. Gram. 1: 62 (1835). 



Santiago Papasquiaro, 472 E. Palmer, August, 1896; about Cuernavaca, State of More- 

 los, 6496 C. G. Pringle, September 16, 1896; Bolanos, State of Jalisco, 3694 J. X. 

 Rose, September 10-19, 1897; east base of Sierra Madre Mountains, State of 

 Chihuahua, 6496 E. W. Nelson, September 29, 1899. 



Aristida schiedeana Trin. & Rupr. Agrost. 3: 120 (1842). 



Near Platea<l< s State of Zacatecas, 2793 J. N. Rose, September 4, 1897. 



Aristida setifolia H. B. K. Nov. Gen. et Sp. PI. 1: 122 (1815). 



Las Sedas, State of Oaxaca, 931, 918 (in part) C. L. Smith, September, 1894. 



Stipa ceerulea Presl, Rel. Haenk. 1: 227 (1830). 



Sierra de San Felipe, altitude 3,075 m., State of Oaxaca, 926 C. L. Smith, Septem- 

 ber 18, 1894. 



Stipa linearifolia Fourn. Mex. PI. 2: 73 (1881) (?). 



Saltillo, State of Coahuila, 3 E. Palmer, April, 1898. Distributed as S. rtridtiJa Trin., 

 from which it is very distinct, and although not agreeing in all particulars with 

 Fournier's description of S. linearifolia, there can be but little doubt as to its 

 identity. Empty glumes equal, acuminate, 7 mm. long; flowering glume 5 mm. 

 long, i)il()se with long appressed hairs; awn scabrous, 1.5-2 cm. long, twisted 

 and twice geniculate. Leaf-l>lades strongly involute, 2-3 dm. long. 



Stipa trochlearis Nees in Meyen, Reise, 1: 484 (1843). 



Durango, State of Durango, 532 E. Palmer, August, 1896. 



Stipa virescens H. B. K. Nov. Gen. et Sp. PL 1: 126 (1815). 



Near Plateado, State of Zacatecas, 2750 J. N. Rose, September 2, 1897. 



Muhlenbergia acuminata Vasey, Bot. Gaz. 11: 337 (1886). 



Saltillo, State of Coahuila, 379 E. Palmer, September, 1898, in rich, moist soil. 



MuMenbergia aflfinis Trin. Agrost. 2: 291 (1841). 



Las Sedas, State of Oaxaca, 952 C. L. Smith, September, 1894; on the road between 

 Mesquitec and Monte Escobedo, State of Jalisco, 2614 J. N. Rose, August 26, 1897; 

 Sierra Madre Mountains, west of Bolanos, 2984 J. N. Rose, September 15-17, 1897. 



*]yEuhlenbergia alamosana Vasey, Bot. Gaz. 16: 146 (1891). 



Mossy cliffs. Sierra de Tepixtlan, near Cuernavaca, altitude 2,300 Tn., 6994 C. G. 

 Pringle, February 8 and March 14, 1899. 



Muhlenbergia arizonica Scribn. Bui. Torr. Bot. Club, 15: 8, pi. 76 (1888). 



Durango, State of Durango, 536, 713 E. Palmer, August, 1896. 



Muhlenbergia berlandieri Trin. Agrost. 2: 299 (1841). 

 Durango, State of Durango, 729 E. Palmer, September, 1896. 



Muhlenbergia calamagrostidea Kunth, Rev. Gram. 1: 63 (1835). 



Durango, State of Durango, 719, 725, 881 E. Palmer, September-October, 1896; near 



Plateado, State of Zacatecas, 2736 J. N. Rose, September 3, 1897. 

 Muhlenbergia capillaris Trin. Gram. Unifl. 191 (1824). 

 SicngH, State of Durango, 859, 960 E. Palmer, November, 1896. 

 Muhlenbergia debilis Trin. Gram. Unifl. 193 (1824). 



Monte Alban, altitude 1,700 m., near Oaxaca, State of Oaxaca, 938 C. L. Smith, Octo- 

 ber S, 1894. 

 MUHLENBERGIA DENSIFLORA Scribn. & Merrill, sp. nov. (Fig. 4.) 

 An erect, rigid, c;espitose i)erennial, 6 to 9 dm. high, with involute, wdry leaves and 

 dense, contracted panicles 7 to 12 mi. long. Culms cylindrical, glabrous, or 



