COMPARATIVE ANALYSIS. 



229 



Panicle lax, not spiked ... 29 



26. Some of the florets with stamens only . . .27 

 Florets perfect . . . . . 28 



27. Spike compound, florets without bristles . . . Panicum. 

 Spike simple, florets with a bristly involucre . . Setaria. 



28. Calyx valves nearly equal, styles united . . . Sesleria. 

 Calyx valves unequal, styles distinct . . . Airochloa. 



29. Corolla awnless . . . . .30 

 Corolla awned . . . . . 31 



30. Glumes truncate . , . . . Catabrosa. 

 Glumes acute ..... Melica. 



31. Florets perfect . .* . . .32 

 Some of the florets with stamens only ... 33 



32. Corolla invested with seed .... Avena. 

 Corolla not invested with seed . . . Aira. 



33. Florets three, perfect one with two stamens . . . Jfierochlce. 

 Florets two, perfect one with three stamens . . 34 



34. Upper floret barren, lower one perfect . . . Holcus. 

 Lower floret barren, upper one perfect . Arrhenatherum. 



35. Panicle imbricated and simple .... Sesleria. 

 Panicle loose, or, if dense, branched . . . 36 



36. Corolla with long hairs at base . . . . Arundo. 

 Corolla without hairs at base, or nearly so . 37 



37 Spikelets in dense clusters at end of the branches . . Dactylis. 



Spikelets not in dense clusters . . . 38 



38. External valve of corolla with three nearly equal teeth . Triodia. 

 External valve of corolla not three-toothed . . 39 



39. Corolla awned or pointed . . . .40 

 Corolla obtuse, not awned .... 42 



40. Corolla with a twisted dorsal awn, upper florets mostly 



imperfect .... Avena. 

 Corolla pointed, or with an awn terminal, or nearly so, 



florets perfect . . . . . 41 



41. Corolla with a terminal awn, or pointed . . . Festuca- 

 Corolla with an awn just below the bifid extremity . Bromus. 



42. Spikelets cordate, (pendulous,) seed coated by the corolla . Sriza. 

 Spikelets not cordate, seeds free ... 43 



43. Spikelets linear or sub-cylindrical, not webbed . . Glyceria. 

 Spikelets ovate or oblong, often webbed . . . Poa. 



TRIANDKIA. Monogynia. 



N AUDITS. 



Florets spiked, unilateral . . . . . Sir iota. 

 TRIANDRIA. Digynia. 



