28 POACEAE 



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

 and slightly on the margins. 

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



Panicle not spike-like. 



Panicle always e.Kserted, 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. 

 Spikelets 4.3-5 mm. long; first glume subulate, usually awned. 7. S. heterolepis. 

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



8. S. asperifolius. 

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



28. POLYPOGON Desf. Beard-grass. i. P. monspelicnsis. 



29. CINNA L. Reed-grass. i. C. lati folia. 



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



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

 the empty glumes; palet nearly as long. 

 Spikelets about 3 nun. long, purple; racliilla one-third to one-half as long as the flower. 



1. A. aequivalvis. 

 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. Thurberiana. 

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

 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, verticillate. 4. A. stolonifera. 

 Empt.v glumes 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 1 ow, slender, 1-3 dm. high; panicle narrow; spikelets about 2 mm. 

 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. re plans. 



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 base. 

 Plant over 3 dm. liigh; empty glumes 2.5-3 ham. long. 



Panicle lobed or interrupted; branches densely verticillate and flower- 

 bearing to the base; empty glumes narrowly lanceolate, gradually 

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

 wide. 10. .4. grandis. 



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

 empty glumes lanceolate, abruptly pointed; ligules 2-4 mm. long, 

 entire or toothed ; leaf-blades 2-5 mm. wide. 11. A. asperifolia. 



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



Basal leaf-blades flat, 2 mm. wide; lemma two-tliirds as long as the 



empty glumes, obtuse. 12. A. Rossae. 



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

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



Panicle open; branches more or less spreadmg, or sometimes I'eflexed. 

 Lemma awnless or with a very short awn. 



Panicle oblong-ovold, 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 filiform, 1 mm. wide or less, usually involute; the basal 



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



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



17. A. hyemalis. 

 Lemma awned; awn equalling or exceeding the glume. 

 Panicle open, difl'use; branches spreading or ascending. 



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



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

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



19. A. Bakeri. 

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



