kfiinoiis margins an<l with few scattered, stiff, papillate hairs on the margins 

 and often on the midnerve beneath. Paniele at length exserted, 18 to 20 cm. 

 long, the axis an<l the erect or ascending simple branches pilose with rather 

 stiff, spreading hairs, the lower ones 5 to 8 cm. long, bearing the approximate but 

 not crowded racemose spikelets in pairs (the upper ones solitary), one nearly- 

 sessile and often imperfectly developed, the other on a pedicel nearly its own 

 length; pedicels pilose. Spikelets oblong or obovate, somewhat pointed, 3-3.5 

 mm. long, the three outer glumes pubescent with short, spreading hairs; first 

 glume deltoid, obtuse, enclosing the base of, and about one-third as long as the 

 spikelet, .5-nerved; second and third glumes prominently ners-ed, subequal, as 

 long as the flowering glume, the second 7-nerved, the third 5-nerved, slightly 

 reticulate-veined above; flowering glume about 3 mm. long, pointed an<l finely 

 transversely rugose. 



Type specimen collected on mesas near Camp Lowell, Santa Cruz Valley, Arizona, 

 465 C. G. Pringle, 1881. 



Other specimens examined: Arizona: Tucson, 1596 D. Griffiths, September, 1900; 

 Bowie, 29 J. W. Toumey, October 1, 1896; no locality, 353 J. G. Lemmon, 1882; 

 sandy plains near the Mexican boundary, C. G. Pringle, August 29, 1884; along 

 streams, Santa Catalina Mountain, 3062 J. G. Lemmon and wife, August, 1883. 

 Xeic Mexico: Mangos, 0. Metcalfe, September 14, 1897.. Texas: near :Madeira 

 Creek, Presidio Co., G. C. Nealley, September, 1892. Mexico: Guaymas, 159, 

 208 E. Palmer, 1887; no locality, 250 E. Palmer, 1897. Loiver California: San 

 Jose del Cabo, 18 T. S. Brandegee, September 4, 1890. 



This species was described by Scribner,^ without name, as '' Paaicum {Virgariu) 

 allied to P. fuscum Sw.," but is certainly distinct from that, and from related 

 species. In some respects it resembles Panicum velutinosum of Trin. Icon. 2: 

 t. 180, but is distinct from the plant there described and also very .listinct from 

 P. velutinomm Xees, Agrost. Bras. 121. 1829, which is certainly different from the 

 plant so considered by Trinius. 



Panicum arizonicum is at once distinguished from related species by its panicle char- 

 acters and especially by its pointed pubescent spikelets. 



PANICUM ARIZONICUM TENUE Scribn. & Merrill var. nov. 



A small, ca-spitose form 1.5 dm. high or less, with smaller leaves and panicles than 

 in the species, the panicle branches 1 to 3 cm. long. Spikelets as in the species. 



Type specimen collected at Fort Huachuca, Arizona, by T. E. ^Yilcox in 1894. Other 

 specimens examined: Mexican boundary line, south of Bisbee, Arizona, 1072 

 E. A. Mearns, October 9, 1892. Tcn/.s.- El Paso, M. E. Jones, September 10, 

 1884. 



PANICUM ARIZONICUM L^VIGLUME Scriljn. & Merrill var. n<jv. 



A low, ca-spitose, much branched form, which differs from Panicum arizonicum tenue 

 only in having glabrous si)ikelets, but which is clearly related to Panicum ari- 

 zonicum rather than to P. fuscum. 



Type specimen collected at Mescal, Arizona, 1810 David Griffiths, October, 1900. 

 Other specimens examined: Cochise, 1810 Griffiths, October, 1900; Fort Hua- 

 chuca, T. E. Wilcox, 1894; Johnson's Ranch, 11 miles east of San Pedro River, 

 :Mexican boundary, 1694 E. C. Merton, August 7, 1893. 



PANICUM ARIZONICUM MAJOR (Vasey) Scrilm. & Merrill n. comb. [Pani- 

 rnin jusrum major Vasey, U. S. Dept. Agr. Div. Bot. Bui. 8: 26. 1889). A stout, 

 erect form 6-9 dm. high, with larger leaves, which are scabrous-punctulate or 

 nearly smooth, scal)rous-punctulate sheaths, and larger, more l)ranched panicles. 



Southwestern Chihualma, 3Iexico, Dr. E. Palmer, August to November, 1885. 



1 Bui. Torr. Bot. Club, 9: 70. 1882. 



