15 



36. Spikeleta not flattened laterally before flowering 49 



37. Awn exceeding 7 mm. long 33 



37. Awn less than 7 mm. long 4j 



38. Flowering glume very broadly lanceolate, subacute, distinctly 7-nerved 



33 B. aleutensis. 



38. Flowering glume lanceolate, acute, usually 5-nerved 39 



39. Flowering glume 18-20 nnn. long; awn 11-15 mm. long 



35/i B. carinatus hookerianus. 



39. Flowering glume 14-16 mm. long; awn 7-10 mm. long 40 



40. Panicle very broad, longest branches 15 mm. or more long, lax and drooping; 



leaves broad 34 B. sitchensis.' 



40. Panicle narrower, longest branches less than 15 mm. long; leaves rather narrow. . 



-• 35a B. carinatus californicus. 



41. Panicle erect or suberect, lower branches rarely more than 10 cm. long 42 



41. Panicle with upper part more or less drooping; lower branches rather weak, the 



longest usually more than 10 cm. long 45 



42. Awn wanting or less than 4 mm. long 43 



42. Awn 4 mm. or more long 44 



43. Spikelets about 1 cm. broad, Briza-like 7 B. brizgeformis. 



43. Spikeleta narrower, not resembling those of Briza 



29a B. unioloides haenkeanus. 



44, Flowering glumes scabrous-pubemlent 45 



44. Flowering glume smooth or merely scabrous 32 B. polyanthus. 



45. Anativeofthesouthwest, Arizona, and southward. 35£B. carinatus arizonicus. 



45. A native of the northwest, Wyoming, Oregon, and northward 



31/S B. marginatus seminudus. 



46. Palea more than three-fourths the length of its glmne 47 



46. Palea three-fourths the length of its glume or less 29 B. unioloides. 



47. Panicle rather lax and open, not dense 48 



47. Panicle large, suberect, and rather dense SSy B. carinatus densus. 



48. Plants with broad leaves, usually more than 7 dm. high 



32a: B. polyanthus paniculatus. 



48. Plants usually less than 7 dm. high with rather short, narrow leaves 



36 B. laciniatus. 



49. Awn distinctly twisted and divaricate 50 



49. Awn not distinctly twisted and divaricate ■. 52 



50. Panicle short and dense 8 B. scoparius. 



50. Panicle rather large and open 51 



51. Spikelets usually more than 5 mm. broad in flower 6 B. squarrosus, 



51. Spikelets 5 mm. or less broad in flower 5 B. patulus. 



52. Panicle short and contracted 53 



52. Panicle rather broad and open 56 



53. Flowering glumes elliptic 3^ B. hordeaceus glabrescens. 



53. Flowering glumes narrow-lanceolate 54 



54. Awn 35 to 40 mm. or more long 11 B. maximus. 



54. Awn less than 30 mm. long 55 



55. Panicle forming a dense head rarely exceeding 5 cm. long 12 B. rubens. 



55. Panicle less dense and usually longer 10 B. madritensis. 



56. Flowering glumes elliptic or ovoid-lanceolate 57 



56. Flowering glumes oblong lanceolate to narrow-lanceolate 60 



57. Margins of flowering glumes not strongly involute in fruit 58 



57. Margins of flowering glumes strongly involute in fruit IB. secalinus. 



58. Panicle rather small and subracemose 2 B. racemosus. 



58. Panicle rather large and broad 59 



