Florets without a pinnated bractea ; ‘ 24 
. Calyx with not more than two perfect florets. 25 
Calyx with more than two perfect florets . 30 
. Panicle dense, in a simple or compound spike . 26 
Panicle lax, not spiked : : ‘ 29 
. Some of the florets with | stamens only : 27 
Florets perfect ‘ : : 28 
. Spike compound, florets without “bristles ; Panicum. 
Spike simple, florets with a bristly involucre i Setaria. 
. Calyx valves nearly equal, styles united : . Sesleria. 
Calyx valves unequal, styles distinct : Aitrochloa. 
Corolla awnless . ; : ‘ BAI 
Corolla awned ; : ‘ ‘ 31 
. Glumes truncate . : : : Catabrosa. 
Glumes acute : ; : : Melica. 
. Florets perfect. F : ou 
Some of the florets with state oat 5 ; 30 
. Corolla invested with seed . : ; . Avena. 
Corolla not invested with seed . ; : Aira. 
. Florets three, perfect one with two stamens. TTierochle. 
Florets two, perfect one with three stamens : 34 
. Upper floret barren, lower one perfect : . Holcus. ~ 
Lower floret barren, upper one perfect. Arrhenatherum. 
. Panicle imbricated and simple : , . Sesleria. 
Panicle loose, or, if dense, branched 3 ‘ 36 
. Corolla with long hairs at base ‘ : . Arundo. 
Corolla without hairs at base, or nearly so dla 37 
. Spikelets in dense clusters at end of the branches . Dactylis. 
Spikelets not in dense clusters . : 38 
. External valve of corolla with three wearin equal teeth = Zriodia. 
External valve of corolla not three-toothed : 39 
. Corolla awned or pointed . : : F 40 
Corolla obtuse, not awned : . 42 
. Corolla with a twisted dorsal awn, upper florets hostly 
imperfect : : ; . Avena. 
Corolla pointed, or with an awn terminal, or nearly so; 
florets perfect .. : : : : 41 
. Corolla with a terminal awn, or pointed . : Festuca. 
Corolla with an awn just below the bifid extremity . Bromus. 
. Spikelets cordate, (pendulous,) seed coated by the corolla Driza. 
Spikelets not cordate, seed free 5 ; 43 
. Spikelets linear or sub-cylindrical, not eblied:. : Glyceria. 
COMPARATIVE ANALYSIS. 229 
Spikelets ovate or oblong, often webbed : ; Pou. 
