58 



7. Flowering glume much firmer in texture than the empty ones, 

 indurated at maturity, when it loosely envelops the grain. 



41. Oryzopsis 



7. Flowering glumes similar in texture to the empty ones, not in- 



durated in fruit. (Section Vilfoe of Sporobolus, maybe looked 

 for here) 53. Epicampes 



8. Rachilla prolonged behind the palea 9 



8. Rachilla not prolonged behind the palea 11 



9. Awn terminal, long and straight, empty glumes minute. 



44. Brachyelytrum 



9. Awn from between the teeth of the bifid apex of the flowering 



glume, short or reduced to a simple mucro 10 



10. Callus of the flowering glume and prolongation of the rachilla 

 naked; panicles loose or expanded 57. Cinna 



10. Callus and prolongation of the rachilla hairy; panicles dense 



and spike-like 61. Ammophila 



11. Empty glumes none; spikelets minute in small umbel-like 



clusters 49. Schmidtia 



11. Empty glumes two 12 



12. Spikelets articulated with the pedicels below the firm and 



awnless empty glumes, falling off entire 55. Limnodea 



12. Spikelets not articulated with the pedicels below the empty 



glumes; flowering glumes 3-nerved and much firmer in tex- 

 ture than the empty ones, at least in fruit. (Section Vilfse 

 of Sporobolus may be looked for here) . . 13. Muhlenbergia 



13. Spikelets articulated with the pedicels below the empty glumes, 



which are much longer than the flowering glume. 



54. Polypogon 



13. Spikelets not articulated with the pedicels below the empty 



glumes 14 



14. Empty glumes saccate at the base, several times longer than the 



flowering glumes; inflorescence contracted and spike-like. 



59. Gastridium 



14. Empty glumes not saccate at the base, and if longer than the 



flowering glume, never exceeding it by more than one-third 

 or one-half 15 



15. Rachilla prolonged behind the palea 16 



15. Rachilla not prolonged behind the palea — 17 



16. Callus of the flowering glume and prolongation of the rachilla 



hairy; empty glumes subequal; flowering glume dorsaily 

 awned 60. Calam agrostis 



