28 POACEAE 



Leaf-blades not widely spreading; sheaths glabrous, except the apex, 

 and sUghtly on the margins. 

 Panicle narrow and spike-like. 4. S. strictus. 



Panicle not spike-like. 



Panicle always exserted, oblong, comparatively narrow; its 

 lower branches but little, if any, exceeding the upper ones. 



5. S. flexuosus. 

 Panicle usually more or less included in the sheath; its lower 

 branches much exceeding the upper ones. 6. S. cryptandrus. 

 Spikelets4.5-5mm.long;flrstglumesubulate,usuaUyawned. 7. S. heterolepis. 

 First glume almost equalling the second; plants with long, scaly rootstocks. 



8. iS. asperifolius. 

 Annuals; empty glumes almost equal, ovate. 10. S. confusus. 



28. POLYPOGON Desf. Bbaed-gbass. l. P. monspeliensis. 



29. CINNA L. Reed-grass. l. C. latifoUa. 



30. AGROSTIS L. Red-top, Bent-grass, Tickle-grass. 



Racliilla prolonged above the palet, naked or minutely pubescent; lemma equalling 

 the empty glumes ; palet nearly as long. 

 SpUcelets about 3 mm. long, purple ; rachilla one-third to one-half as long as the flower. 



1. A. aeauivalvis. 

 Spikelets about 2 mm. long; rachilla less than one-third as long as the flower. 



Empty glumes dark purple, broadly lanceolate, abruptly acute or acuminate; 



inflorescence short and open; stem few-leaved. 2. A. atrata. 



Empty glumes green, only tinged with purple towards the tip, narrowly lanceolate, 

 gradually acute; Inflorescence long and narrow; stem leafy. 3. A. Thurieriana. 

 Rachilla not prolonged above the palet; lemma shorter than the empty glmnes. 

 Palet evident, 2-nerved, at least one-fourth as long as the lemma. 



Empty glumes obtuse, scabrous on the back; panicle dense; branches flower- 

 bearing from the base, verticiUate. 4. A. siolonifera. 

 Empty glum&s acute or acuminate, glabrous or scabrous on the keel only. 

 Plant erect or decumbent at the base, but not extensively stoloniferous. 



Plant tall, usually over 3 dm. high; panicle large, open; spikelets over 2 



mm. long. 5. A. alba. 



Plant low, slender, 1-3 dm. high; panicle narrow; spikelets about 2 nmi. 

 long or less. 

 Lemma nearly as long as the empty glumes; palet about two-thirds as 



long as the lemma; plant erect. 6. A. humilis. 



Lemma one-third shorter than the empty glumes; palet about one-half as 

 longas the lemma; plant decumbent at the base. 7. A. depressa. 

 Plant extensively stoloniferous; stolons with short leaves; palet one-fourth to 

 one-half as long as the lemma. 8. A. reptans. 



Palet lacking or minute. 



Plant with creeping rootstock. 9. A. foliosa. 



Plant tufted, without creeping rootstock. 



Panicle dense and narrow; branches ascending or erect, flower-bearing to 

 near the bsise. 

 Plant over 3 dm. high; empty glumes 2.5-3 mm. long. 



Panicle lobed or interrupted; branches densely verticiUate and flower- 

 bearing to the base; empty glumes narrowly lanceolate, gradually 

 attenuate; hgules 4—5 mm. long, lacerate; leaf-blades 6-10 mm. 

 wide. 10. A. grandis. 



Panicle usually contiguous; branches few and some naked at the base; 

 empty glumes lanceolate, abruptly pointed; ligules 2^ mm. long, 

 entire or toothed ; leaf-blades 2-5 mm. wide. 1 1 . A . asperifolia. 



Plant 1-2 dm. high; empty glumes 2 mm. long or less. 



Basal leaf-blades flat, 2 nun. wide; lemma two-thirds as long as the 



empty glumes, obtuse. 12. A. Bossae. 



Basal leaf-blades 1 mm. wide or less, conduphcate; lemma three-fourths 

 as long as the empty glumes, acute. 13. A. variabilis. 



Panicle open; branches more or less spreading, or sometimes reflexed. 

 Ijcrama awnless or with a very short awn. 



Panicle oblong-ovoid, its branches ascending. 



Plant 1-4 dm. high; empty glumes unequal, 1.5-2 mm. long. 



14. A. idahoensis. 

 Plant 3-6 dm. high; empty glumes equal or nearly so, 3 mm. long. 



15. A. oregonensis. 

 Panicle triangular-ovoid or broadly conic; branches at least in age 



divaricate or even reflexed. 

 Leaf-blades flUform, 1 mm. wide or less, usually involute; the basal 



ones numerous; upper sheaths close. 16. A. oreophila. 



Leaf-blades iisually flat, 1—3 mm. wide; upper sheaths loose. 



17. A. hyemalis. 

 Lemma awned; awn equalling or exceeding the glume. 

 Panicle open, diffuse; branches spreading or ascending. 



Leaf-blades about 0.5 mm. wide; panicle broadly conic; branches 



very scabrous, in age spreading or reflexed. 18. A. geminata. 

 Leaf-blades 1-2 mm. wide; panicle ovoid; branches ascending. 



19. A. Bakeri. 

 Panicle narrow; branches nearly erect. 20. A. melaleuca. 



