COMPAEAIIVE ANALYSIS. 



229 



Florets ■without a pinnated bractea . . 24 



24. Calyx with, not more than two perfect florets . 25 

 Calyx with more than two perfect florets . . 35 



25. Panicle dense, in a simple or compound spike . 26 

 Panicle lax, not spiked ... 29 



26. Some of the florets with stamens only . 27 

 Florets perfect .... 28 



27. Spike compound, florets without bristles . ranicum. 

 Spike simple, florets with a bristly involucre . Setaria. 



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

 Calj'x valves unequal, styles distinct . . Airochha. 



29. Corolla awnless . . . . .30 

 Corolla awned . . . . 31 



30. Glumes truncate .... Catabrom. 

 Glumes acute .... 2Ielic(i. 



31. Florets perfect .... 32 

 Some of the florets with stamens only > . 33 



32. Corolla invested with seed .... Avem. 

 Corolla not invested with seed . > . . Aira. 



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

 Florets two, perfect one with three stamens . 34 



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

 Lower floret barren, upper one perfect . Arrhenatherum. 



35. Panicle imbricated and simple . . ■ Sesleria. 

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



36. CoroUa with long hairs at base . . • Arimdo. 

 Corolla without hairs at base, or nearly so . 37 



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

 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 .... 

 Corolla obtuse, not aWned 



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



imperfect . . . . • 



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



florets perfect . . . • • 



41. Corolla with a terminal awn, or pointed . 

 Corolla with an awn just below the bifid extremity 



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

 Spikelets not cordate, seed free 



43. Spikelets linear or sub -cylindrical, not webbed 

 Spikelets ovate or oblong, often webbed 



40 



42 



Avena. 



41 



Festuca. 



Bromus. 



Briui. 



43 



Glyceria. 



Poa. 



