14 



15. Sheaths without a ring of pilose jjubescence at the base of the blade 16 



15. Sheaths with a ring of pilose pubescence at the base of the blade 



20a B. purgans latiglumis. 



16. Sheaths densely soft pilose-pubescent 21?^ B. purg-ans incanus. 



16. Sheaths sparsely pilose-pubescent or nearly smooth 2 1 B. purgans. 



17. Flowering glumes acute or subacute with not more than 5 distinct nerves ... 18 



17. Flowering glumes broad, obtuse or sub-obtuse, 7-nerved 22 



18. Awn of flowering glume straight at maturity 19 



18. Awn more or less twisted and divaricate at maturity 21 



19. Branches of the panicle rather rigid and spreading in fruit . 22 B. orcuttianus. 



19. Branches of the panicle not rigid nor broadly spreading 20 



20. Leaves of the innovations narrow and involute 26 B. erectus. 



20. Leaves not involute and panicle not strictly erect . . 21yS B. purgans texensis. 



21. Panicle more than 2 dm. long 9cr B. trinii pallidiflorus. 



21. Panicle smaller; mostly le3s than 2 dm. long 9 B. trinii. 



22. Awn twisted and divaricate at maturity 23 



22. Awn not conspicuously twisted or divaricate 3B. hordeaceus. 



23. Panicle dense; usually less than 12 cm. long. . 3a: B. hordeaceus intermedius. 



23. Panicle looser; more than 15 cm. long 9 /i B. trinii excelsus. 



24. Leaves of the innovations numerous, narrow 35^ B. carinatus linearis. 



24. Leaves of the innovations few; more than 2 mm. broad 35 B. carinatus. 



25. Panicle rather broad, loose and drooping 26 



25. Panicle rather narrow and erect or not conspicuously drooping 31 



26. Awn more than 6 mm. long ^. . 27 



26. Awn less than 6 mm. long 29 



27. An introduced species with broad, loose panicle 1 5 B. ramosus. 



27. Xative species, with rather narrow panicles , 28 



28. Leaves and sheaths glabrous; leaves usually more than 7 mm. broad 



23a: B. vulgaris eximius. 



28. Leaves and sheaths more or less pilose-pubescent; leaves less than 7 mm. broad 



23^ B. vxilgaris robustus. 



29. Flowering glume pubescent above the middle on the margin and across the lower 



half of the back 30 



29. Flowering glume ciliate-pubescent on the margin, the jjubescence extending very 



little above the middle. 31 



30. Ligule 2 mm. or more long; plants with creeping rootstocks 24 B. laevipes. 



30. Ligule less than 2 mm. long; plants without creeping rootstocks 



17B. richardsoni. 



31. Native of the Rocky Mountains westward and northward 



1 la B. richardsoni pallidus. 



31. Native of the Northeastern States and northward 16 B. ciliatus. 



32. Panicle broad, branches widely spreading in flower, introduced. . 27 B. inermis. 



32. Panicle rather narrow with erect or ascending branches 33 



33. Panicle narrow and rather rigidly erect; flowering glume short-pubescent or 



puberulent on the margin 25 B. suksdorfii. 



33. Panicle not rigidly erect 34 



34. Awn wanting or not exceeding 2 mm.; flowering glume Avith margin short- 



pubescent 28/i B. pumpellianus melicoides. 



34. Awn usually exceeding 2 mm 35 



35. Margin of the flowering glume very densely ciliate-pubescent nearly to the apex 



28a: B. pumpellianus tweedyi. 



35. Margin of the flowering glume with shorter pubescence not reaching to the 



apex 28 B. pumpellianus. 



36. Spikelets large, somewhat laterally compressed before flowering 37 



