14 



GRAMINEAE 



Empty glumes very dissimilar in 



outline. 

 Empty glumes similar in out- 

 line. 

 Panicle spike-like. 

 Panicle open. 

 Flowering glumes 5-many-nerved . 

 Glumes papery. 

 Glumes not papery. 

 Glumes strongly keeled. 

 Glumes awned. 

 Glumes not awned. 



Large spikelets in drooping 



panicles. 

 Spikelets erect. 

 Plants dioecious. 

 Plants not dioecious. 

 Glumes rounded on back. 

 Flowering glume awned. 

 Spikelets strongly pedicel- 

 led. 

 Spikelets nearly sessile. 

 Flowering glume awnless, ob- 

 tuse and scarlous at apex. 

 Flowering glume awnless, acute 

 at apex. 



C. 



Spikes digitate. 

 Spikes not digitate. 



Spikelets with two or more perfect 



flowers. 

 Spikelets with one perfect flower. 

 Spikes long and very slender. 

 Spikes short and broad. 



D. 



Spikes one to each joint of the raohis. 

 Placed edgewise on the rachis. 

 Placed flatwise on the rachis. 

 Spikelets two or more to each joint of the 

 rachis. 

 Empty glumes waiting. 

 Empty glumes present. 

 Spikelets all perfect. 

 Spikelets three at each joint, the lat- 

 eral ones sterile. 



40. Eatonia. 



41. koblbkia. 

 39. Eeagbostis. 



42. Mblioa. 



46. Dactylis. 



44. TJniola. 



45. DiSTICHLIS. 



47. POA. 



50. Bromhs. 

 49. Fbstuca. 



48. Panioulaeia. 



49. Fkstuca. 



34. Eleusine. 



35. Leptochloa. 



31. schedonnardtjs. 



32. bouteloua. 



51. LOLIDM. 



52. Aqropyron. 



55. Hystrix. 



54. Elymus. 



53. HOEDEUM. 



1. TRIPSACXJM L. 



Tall perennial grasses with monoecious flowers in jointed spikes which 

 are staminate above and pistillate below. Staminate spikes two-flow- 

 ered, in pairs at each node. Glumes four, the outer coriaceous, the inner 

 thin. Pistillate spikelets one-flowered, deeply imbedded in the thick 

 rachis. Stigmas conspicuous, purple. 



