GRIFFITHS THE GRAMA GRASSES. 391 



it is most abundant, "black grama" is the name by which the stockmen know it. 

 In and adjacent to the Mesilla Valley it occupies large stretches of the open, gently 

 sloping country between the rugged upper foot-hills and the brushy regions of the 

 lower foothills and mesas above the bottom lands. The crop here in exceptionally 

 favorable years is heavy enough to be mown for hay. No other region is known which 

 makes such a heavy crop, although it is an abundant and familiar grass throughout 

 the arid Southwest and extends far into Mexico. 



There has never been much confusion regarding its identity, and although very 

 variable the species is easily distinguished when once recognized. Wright 18 and 

 748; Jones 54a; Pringle 411; Mearns 2267 and 2089; and Wooton 458 are typical. 



HERBARIUM SPECIMENS. 



Arizona: Griffiths 1825, Mescal; 1669, Rincon Mountains; 3395 and 3367, Santa Rita 

 Forest Reserve. Jones 6067, Pipe Spring; 4262, Bowie; Griffiths & Thornber 1, 

 Santa Rita Forest Reserve; 233, Empire Ranch. Leibcrg 5931, Bright Angel Trail, 

 Grand Canyon. Mearns 865, south of Bisbee; Rusby 892, Yavapai County. 

 Purpus 8276, Beaver Creek. Tourney. Chiricahua Mountains. 



New Mexico: Plank 18 and 5, Socorro. Griffiths 3337, Deming. Mearns 2333, Dog- 

 Mountains. Metcalfe 631, 1451, Kingston; Wright 2018; Jones 54a, Albuquerque. 

 Wooton & Standley, Tortugas Mountains; 3973, east of Dona Ana Mountains. 

 Hitchcock 3740, Deming; 3787, Organ Mountains. Wooton 458, Las Cruces. 



Texas: Plank 69, El Paso. Tracy 8283, Barstow. Carleton 417, Oldham County. 



Mexico: Pringle 411, Chihuahua. Wilkinson 348, Santa Eulalia Plains, Chihuahua. 

 Mearns 2089, base of San Luis Mountains, Mexican Boundary. 



16. Bouteloua rothrockii Vasey. 



Bouteloua polystachya major? Vasey in Wheeler, Rep. IT. S. Surv. 100th Merid. 

 6: 287. 1878. This is based upon Rothrock's no. 691, Sonoyta Valley, Arizona, 

 September, 1874. The specimen is in the National Herbarium. It is the narrow- 

 spiked form, typical of B. micrantha Scribn. & Merr. See also Vasey, Grasses U. S. 

 33. 1883, and Descr. Cat. Grasses 63. 1885. Both this variety and B. rothrockii are 

 listed in the former reference. 



Bouteloua rothrockii Vasey, Grasses U. S. 33. 1883, name only; Contr. Nat. Herb. 

 1 : 268. 1893, containing the first description. The type is Rothrock's no. 347, Cot- 

 tonwood, Arizona, 1874. See also U. S. Dept. Agr. Div. Agrost. Bull. 7 : 221./. 203. 

 1897. 



Bouteloua micrantha Scribn. & Merr. U. S. Dept. Agr. Div. Agrost. Circ. 32 : 8. 

 1901. Based upon Griffiths 1556, Fort Lowell, Arizona, September, 1900. This is a 

 narrow-spiked form of B. rothrockii grown under favorable circumstances in an irri- 

 gated, poorly cultivated field. It is typical of B. polystachya major ? Vasey. 



DESCRIPTION. 



A tufted, erect, sparingly branched, smooth, short-lived perennial, 25 to 50 cm. 

 high; sheaths striate, smooth, rather tightly fitting but often open at maturity, the 

 ligule reduced to a ciliate fringe; blades abundant toward the base of culm, 6 to 10 cm. 

 long, 2 to 3 mm. wide, smooth or usually with a few long, scattered, delicate, papillose 

 hairs on the upper surface and edges, the margin minutely serrate; panicle racemose, 

 10 to 25 cm. long; spikes 4 to 10 or 12, 2.5 to 3 cm. long and 5 mm. wide; spikelets 

 pectinate, 40 or 50, about 6 mm. long, including awns; glumes minutely scabrous, 

 keeled, the first about one-half the length of the second and with an awn about 1 mm. 



