MANUAL OF THE GRASSES OF THE UNITED STATES 423 



the summit sometimes expanded into a crown; awn deciduous or 

 persistent, curved, flexuous or geniculate, often twisted below; palea 

 narrow, indurate, except toward the margins, central keel consisting 

 of two nerves and a narrow channel or sulcus between, the apex of 

 the keel projecting above the summit of the lemma as a minute point. 

 Tufted perennials with narrow usually involute blades and rather 

 few-flowered panicles. Type species, Piptochaetium setifolium Presl. 

 Name from Greek piptein, to fall, and chaite, bristle, alluding to 

 the deciduous awns of the type species. 



1. Piptochaetium fimbriatum(H.B.K.) Hitchc. Pinyon ricegrass. 

 (Fig. 883.) Culms densely tufted, erect, slender, 40 to 80 cm tall; 

 blades involute-filiform, flexuous, elongate; 

 panicle open, 5 to 15 cm long, the slender 

 branches spreading, few-flowered toward the 

 ends; spikelets long-pediceled ; glumes about 5 

 mm long, abruptly acuminate, 7-nerved ; lemma 

 a little shorter than the glumes, appressed- 

 pubescent, especially on the callus, dark brown 

 at maturity with a circular ridge at the base of ^SKS. ' 

 the awn; awn weakly twice geniculate, 1 to 2 cm 



long. Ql (Oryzopsisjimbriata Hemsl.) — Open rocky woods, Colorado 

 to western Texas, Arizona, and Mexico (fig. 884). A fine forage grass. 



84. STIPA L. Needlegrass 



Spikelets 1 -flowered, disarticulating above the glumes, the articu- 

 lation oblique, leaving a bearded, sharp-pointed callus attached to the 

 base of the floret; glumes membranaceous, often papery, acute, 

 acuminate, or even aristate, usually long and narrow; lemma narrow, 

 terete, firm or indurate, strongly convolute, rarely the margins only 

 meeting, terminating in a prominent awn, the junction of body and 

 awn evident, the awn twisted below, geniculate, usually persistent; 

 palea enclosed in the convolute lemma. Tufted perennials, with 

 usually convolute blades and mostly narrow panicles. Type species, 

 Stipa pennata L. Name from Greek stupe, tow, alluding to the 

 feathery awns of the type species. 



The species are for the most part valuable forage plants. Several, 

 all western, such as Stipa comata, S. occidemalis , S. lemmoni, and 

 S. neomexicana, are grazed chiefly when young. Stipa letiermani is 

 important at high altitudes, in the mountains of the West; S. Colum- 

 biana at medium altitudes; S. viridula in the Rocky Mountains; S. 

 pulchra, S. thurberiana, and S. speciosa in California. Some of the 

 species, when mature, particularly S. spartea and S. comata, are 

 injurious, especially to sheep, because of the hard sharp points to the 

 fruits which penetrate the skin. Sleepy grass, S. robusta, acts as a 

 narcotic (see p. 436). One of the Old World species, S. tenacissima L., 

 furnishes a part of the esparto or alfa grass of Spain and Algeria that 

 in used in the manufacture of paper and cordage (see p. 439). 



la. Terminal segment of awn plumose. 



Awn 12 to 18 cm long 1. S. neomexicana. 



Awn 1.2 to 1.5 cm long 15. S. porteri. 



lb. Terminal segment of awn not plumose. 



2a. First segment of the once-geniculate awn strongly plumose, the ascending 



hairs 5 to 8 mm long 2. S. speciosa. 



2b. First segment of awn sometimes plumose but the hairs not more than 2 mm 

 long. 



