r 1 1 I . ( J K A SS KS OF T KN N KSS K K. 87 



6. Spikclets not crowded in spike-like panicles, second {^Muine 



not vjibbous at base 7 



7. Leaves all alike, spikelets acute. [IJotnophylLc.) 8 



7. Leaves dissimilar, those at the base shorter and broader 



than those above; leaves on the branches usually much 

 smaller and more crowded than those on the primary 

 stem; spikelets blunt or obtuse [P. depauperaUun ex- 

 cepted). {Jl(ierophyllic) 15 



8. Perennials 9 



8. Annuals 12 



9. Culms stout, 2-5 feet high 10 



9. Culms slender, 1-2 feet high 14 



10. Spikelets i-i.V lines long, culms compressed, branching . . i i 



10. Spikelets 2-2I lines long, culms terete, simple 



. . . ". 9. P. VIRGAIUM. 



1 1, Spikelets i.^ lines long, fertile floret sessile within the glumes 



, . . ." 7. P. ANCtPS. 



1 1. Spikelets i-i \ lines long, fertile floret raised on a very short 



pedicel 8. P. agrostotdes. 



12. Sheaths somewhat flattened and with the leaves glabrous, 



first glume broadly obtuse .... 10. P. proliferum. 



12. Sheaths pilose or hirsute, first glume acute 13 



13. Spikelets i line long or less, panicle branches spreading 



II. P. capillare. 



13. Spikelets i.} lines long, panicle branches ascending . . . 



. , . .' 12. P. flexile. 



14 Outer glumes striate, palea of the third glume inflated, rigid, 

 as long as the glume and apiculate ... 13 P. hians. 



14. Outer glumes warty-roughened (verrucose), palea of the 



third glume inconspicuous . . . . 14. P. VERRUcosu.^L 



15. Spikelets exceeding i line in length 16 



15. Spikelets i line long or less 21 



16. Leaves ovate or broadly lanceolate, more or less cordate at 



the base 17 



16. Leaves very narrowly lanceolate or linear 20 



17. Culm stout, 3-4 feet high, sheaths usually rough-hispid 



15. P. CLAN1)EST1NL>L 



17. Culms more slender, 1-2 feet high, sheaths not hispid, smooth 



or pubescent 18 



18. Glume of fertile floret pubescent at the apex, leaves broadly 



ovate lanceolate, spikelets ovate-elliptical. 17. P. Walterl 



18. Glume of the fertile floret not pubescent at the apex ... 19 



19. Leaves broadly lanceolate, thin, and conspicuously many- 



nerved, cordate, clasping at the base, glabrous, as are the 

 sheaths. Panicle compound, branches capillary, naked 

 below; spikelets ovate-elliptical; second and third glumes 



7-nerved 21. P. commutatlm. 



19. Leaves narrower, nerves not conspicuous, sheaths usually 



