GBAMINE.E. (GRASS FAMILY.) 575 



TRIBE VI. AGROSTIDE^E. Spikelets l-flo\vered, rarely with a rudiment or second 

 flower above. Glumes 3, the two lower empty. Palea rarely wanting. Inflorescence 



panicled. 



* Glumes niembranaceons or chartaceous. 



- Empty glumes united below, conduplicate. 



29. ALOPECURUS. Flowering glume dorsally awned. Inflorescence spiked. Palea none. 



H- -i- Glumes separate, convex or keeled. 



30. SPOROBOLUS. Spikelets awnless. Flowering glume 1-nerved, longer than the un- 



equal empty ones. 



31. AGROSTIS. Spikelets mostly awned. Flowering glume 3-5-nerved, thin, shorter 



than the nearly equal empty ones. Palea small or none. 



32. POLYPOGON. Empty glumes long-awned. Panicle spike-like. 



33. CINNA. Spikelets flattened. Flowering glume awned below the apex. Stamen 1. 



34. CALAMAGR.OSTIS. Spikelets 1-flowered, and often with the pedicel of a second 



flower. Floret surrounded by a tuft of long hairs. 



* * Flowering glume awned at the tip (except No. 35) of a firmer texture, closely investing 



the grain. 



35. THURBERIA. Flowering glume awned below the tip. 



36. STIPA. Flowering glume with a single long twisted awn. 



37. ARISTIDA. Flowering glume triple-awned. 



38. MUHLENBERGIA. Empty glumes unequal. Floret hairy at the base, mucronate or 



straight awned. 



39. BRACHYELYTRUM. Empty glumes very small. Floret long-awned. Stamens 2. 



TBIBE VII. AVENEjE. Spikelets 2 - several-flowered, the terminal one mostly rudi- 

 mentary. Rachis or base of the flowers often bearded. Flowering glume awned on 

 the back or below the apex. Spikelets pauicled. 



* Flowers perfect, or the uppermost rudimentary. 



40. AIRA. Spikelets 2-flowered. Flowering glume 2-cleft. 



41. DESCHAMPSIA. Spikelets 2-ttowered, and with a hairy rudiment. Flowering glume 



truncate, toothed. 



42. TRISETUM. Spikelets 2 - several-flowered. Flowering glume compressed, keeled, 



awned. 



43. DANTHONIA. Spikelets 2 - several-flowered. Flowering glume rigid, 2-cleft, the 3 



middle nerves united into a twisted awn. 



* * Spikelets 2-flowered, one perfect, the other staminate. 



44. HOLCUS. Upper flower stamiuate and awned. Glumes keeled. 



45. ARRHENATHERUM. Lower flower staminate and long-awned. Glumes concave. 



TRIBE VIII. CHLORIDEJE. Spikelets 2 - several- (rarely 1-) flowered, in 2 rows in 

 racemose or digitate (rarely solitary) spikes. Upper flowers imperfect. 



* Spikelets strictly 1-flowered, awnless. 



46. SPARTINA. Spikes racemed. Spikelets flat. Glumes keeled. 



* * Spikelets 2- 3-flowered, the lowest flower perfect. 



47. GYMNOPOGON. Spikelets linear, scattered. Flowering glume and rudiment awned. 



Spikes racemed, filiform. 



48. BOUTELOUA. Spikes short, dense, racemed. Flowering glume 3-toothed. 



49. CHLORIS. Spikes digitate. Spikelets roundish. Flowering glume mucronate. 



50. CYNODON. Spikes digitate, slender. Flowering glume awnless. Culms creeping. 



* * * Spikelets 4 - 5-flowered, only one of the middle ones perfect. 



51. CTENIUM. Spike solitary. Flowering glume stout-awned on the back. 



* * * * Spikelets several-flowered, the lower flowers perfect. 



52. ELEUSINE. Spikes digitate. Spikelets crowded or imbricate. 



