GRASS FAMILY 25 



Stem and sheaths densely soft- pubescent ; hairs scarcely papillate. 



8. P. thermale. 

 Spikelets more than 2 mm. long. 



Blades of stem-leaves elongated, narrowly linear 



Spikelets glabrous or with a few scattered hairs; stem branching only 



at the base. 9. P. perlongum. 



Spikelets densely pubescent; stem brandling above. 



10. P. Wilcoxianum. 

 Blades of stem-leaves lanceolate. 11. P. Scribnerianum. 



I/ifiorescence with racemiform branches. 12. P. oblusum. 



11. ECHINOCHLOA Beauv. Barnyard Gr.\ss, Jungle Rice. i. E.Crus-galli. 



12. CHAETOCHLOA Scribn. Foxtail Gras.s. 



Inflorescence with the spikelets racemosely arranged; bristles 5-16 at the base of each 



spikelet, involucrate, tawny-orange. 1. C. glauca. 



Inflorescence with the spikelets in clusters on the branches; bristles 1-3 at the base of 

 each spikelet, not involucrate. 

 Second glume of the spikelet as long as the lemma, or very nearly so; annuals. 



Panicle usually 1 cm. tliick or less; bristles commonly green; spikelets about 2 



mm. long. 2. C. viridis. 



Panicle usually 1-3 cm. thick; bristles usually purple; spikelets 2.5-3 mm. long. 



3. C. italica. 

 Second glume manifestly shorter than the lemma; perennials. 4. C. composila 



13. CENCHRUS L. Bur-grass, Sandbur, Sandspur. i. C. caroUnianus. 



14. HOMALOCENCHRUS Mieg. Rice Cut-grass. i. H. oryzoides. 



15. PHALARIS L. Canary-grass. 



Outer glumes not winged: inflorescence a narrow panicle. 1. P. arundinacea. 



O uter glumes winged ; inflorescence a spike or spike-like panicle. 



Spikelets narrow; third and fourth glumes much reduced; blades subulate-linear, 

 hairy. 2. P. caroliniana. 



Spikelets broad; third and fourth glumes thin, membranous; blades lanceolate, 

 glabrous, rarely sparingly hairy. 3. P. canariensis. 



16. TORRESIA R. & P. Sweet Grass, Holy Grass. i. T. odorata. 



17. ARISTIDA L. Poverty Grass, Wire-grass. 

 Awns neither twisted nor bent. 



Panicle narrow; branches erect or ascending. 

 First tilume much shorter than the second. 



Spikelets not crowded, usually 1-3, on branches naked at the base; awn over 

 2 era. long; peremiials. 

 Second glume of the spikelets 2 cm. long or more, 1.5-2 times as long as the 



lemma. 1. A. longiscta. 



Second glume of the spikelets 1.5 cm. long or less, scarcely exceeding the 

 lemma. 2. A. Fendleriana. 



Spikelets crowded, 4-6 on the short branches, spikelet-bearing to near the 

 base; awn less than 2 cm. long; annuals. 

 Stem 3-6 dm. high; first glume 7-8 mm. long; middle awn 10-16 mm. long 



leaf-blades usually flat. 3. A. fasciculata. 



Stem 1-3 dm. high; first glume 4-6 mm. long; middle awn 6-8 mm. long; 

 leaf-blades strongly involute. 4. A. bromoides. 



First glume nearly equalhng the second; perennials with a dense panicle. 



7. A. arizonica.. 

 Panicle open; branches 3-forked, divergent. 5. A. Humboldtiana. 



Middle awn twisted and divaricately bent near the base. 6. A. Curtissii 



18. STIPA L. Spear Gr.iss, Porcupine Gr.\ss, Devil's Darning-needles, 



Feather Grass. 



Outer glume of the spikelet 2 cm. long or more. 



Awn plumose. 1. S. neo-mexicana. 



Awn not plumose. 



Base of the panicle exserted; lemma more than 12 mm. long; a^vn straight above 

 the bend. 

 Lemma 20-25 mm. long. 2. S. spartea. 



Lemma 12-15 Tnm. long. 3. S. Tweedyi. 



Jase of the panicle usually included m the upper sheath; lemma 8-12 mm. long; 

 awn slender and curled above the bend. 4. S. comata. 



Outer glume of the spikelet 1.5 cm. long or less. 



Panicle loose and open; branches spreading or reflexed. 



Awn plumose. 5. S. Porteri. 



Awn not plumose. 



Callus acute; lemma 7-8 mm. long. 6. S. Richardsonii. 



Callus short, blunt; lemma about 4 mm. long. 7. S. canadensis. 



Panicle dense and spike-like. 



Awn glabrous, scabrous, or strigose, not plumose. 



