GRAMINE^E. (GRASS FAMILY.) 421 



7-flowered : outer glumes acute, rough on the back : flowering glume with a 

 broadly scarious irregularly erose apex, the lower half of the middle and marginal 

 nerves usually silky-pubescent. P. andina, Nutt., not of Trin. From California 

 to Wyoming, Colorado, and southward. 



2. P. tenuifolia, Nutt. Stems very slender, densely tufted, 1 to 2 feet 

 high, the foliage glabrous or scabrous : radical tufts 3 or 4 inches high, of ex- 

 ceedingly narrowly linear mucronate-pointed leaves ; stem-leaves scarcely wider : 

 panicle 2 to 6 inches long, the erect rarely spreading distant rays mostly in 

 threes ; spikelets mostly 3-flowered : outer glumes very acute, rouo-h on the 

 midnerve : flowering glume narrowly lanceolate, often erose at the apex, puberu- 

 lent or with a few scattered hairs near the base. From Colorado to California 

 and Oregon. One of the most valuable of the " Bunch Grasses." 



2. Flowering glume compressed -keeled, acute. 



* Low and spreading, or tufted alpine species, flaccid or rigid. 



+- Root annual: branches of the short panicle single or in pairs. 



3. P. annua, L. Stems (3 to 6 inches high) flattened, geniculate below, 

 weak: leaves bright green, short, obtuse, sometimes wavy: panicle often 

 1 -sided ; spikelets very short-pedicelled, 3 to 7-flowered. Everywhere in cul- 

 tivated and waste grounds, generally introduced, but probably indigenous on 

 our southern border in Arizona, New Mexico, W. Texas, etc. 



*- <- Stems geniculate-ascending from a running rootstock, rigid, very much flat- 

 tened: panicle simple and contracted. 



4. P. compressa, L. Pale, as if glaucous : leaves short : panicle dense 

 aud narrow, somewhat 1-sided, the short branches mostly in pairs ; spikelets 

 almost sessile, 3 to 10-flowered, flat. Indigenous within our range at the 

 northeast, and common eastward in sterile soil. Known as " Wire Grass." 



H- -t- - Low mountain or alpine species, erect in perennial tufts. 

 *-- Leaves broadly linear, short and flat, short-pointed; ligule elongated. 



5. P. alpina, L. Soft and flaccid, smooth or nearly so, even to the 

 branches of the panicle : stems rather stout, 6 to 18 inches high : stem-leaves 

 l to 2 inches long, l to 3 lines wide : panicle short and broad; spikelets 

 broadly ovate, 3 to 9-flowered. Frequent in the mountains and extending 

 northward and eastward. Extremely variable, some of the numerous forms 

 being described as varieties. 



w- -I-*- Leaves narrowly linear or setaceous. 



6. P. laxa, Hoenke. Soft and smooth as in the last : stems slender, 3 to 

 10 inches high: leaves narrowly linear; ligule elongated: panicle somewhat 

 raceme-like, narrow, often 1-sided and nodding; spikelets 2 to 4-flowered. 

 In the Rocky Mountains and eastward in the mountains of New York and 

 New England. 



7. P. CSBSia, Smith. More strict and rigid, roughish, especially the panicle : 

 stems 6 to 20 inches high : leaves short, soon involute; ligule short: branches 

 of the panicle 2 to 5 together, very scabrous ; spikelets 2 to 5-flowered : outer 

 glumes ovate lanceolate and taper-pointed. In the Rocky Mountains and 

 eastward. 



Var. strictior, Gray, is 6 to 12 inches high, with a contracted grayish- 

 purple panicle of smaller flowers. Same range as the type. 



