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 branching above. 



10. P. Wilcoxianum. 

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



1 nfiorescence with racemiform branches. 12. P. obtusum. 



11. ECHINOCHLOA Beauv. Barnyard Grass, Jungle Rice. i. E.Crus-gaiH. 



12. CHAETOCHLOA Scribn. Foxtail Grass. 



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



spikelet, iuvolucrate, 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. thick or less; bristles commonly green; spikelets about 2 



mm. long. 2. C. viridis. 



Panicle iisually 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. composita. 



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



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



15. PHALARIS L. Canary-grass. 



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



Outer glumes winged; inflorescence a spike or spike-Uke 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. l. T. odorata. 



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



Awns neither twisted nor bent. 



Panicle narrow; branches erect or ascending. 

 First glume much shorter than the second. 



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

 2 cm. long; perennials. 

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



lemma. 1. A. longiseta. 



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 equalUng the second; perennials with a dense panicle. 



7. A. aHzonica,. 

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



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



18. STIPA L. Spear Grass, Porcupine Grass, 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; awn straight above 

 the bend. 

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



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



jia.se of the panicle usually included in 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. Porleri. 



Awn not plumose. 



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



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



Panicle dense and spike-Uke. 



Awn glabrous, scabrous, or strlgose, not plumose. 



