232 



COMPARATIVE ANALYSIS. 



Spikelets greenish brown 

 Florets awnless 

 Spike bluish, ovate 

 Spikes alternate ". t 



ARRHENATHERTTM. 



HlEROCHL(E. 



SESLERIA. 



PANICUM. 



SETARIA. 



Bristles of involucre with reflexed teeth 

 Bristles of involucre with erect teeth . 



1. 



GLYCERIA, (PoA, Hooker.) 



Florets with seven or more ribs 

 Florets with not more than five ribs 



2. Panicle much branched, plant four feet high 



Panicle slightly branched, plant not more than three feet 

 high .... 



3. Panicle compact, rigid 

 Panicle spreading, not rigid 



4. Root creeping .... 

 Root fibrous 



5. Forets four or five, five-ribbed, plant procumbent . 

 Florets six or seven, nearly ribless, plant erect, or ascending 

 Panicle reflexed in fruit 



6. 



Panicle not reflexed in fruit 



POA. 



1. Florets webbed .... 

 Florets not webbed .... 



2. Stems bulbous at base 

 Stems not bulbous at base 



3. Culm much compressed, spikelets three or more flowered 

 Culm round, or but little compressed, spikelets three or 



four-flowered . . . 



4. Florets obscurely ribbed, panicle somewhat drooping 

 Florets five-ribbed, panicle not drooping 



5. Ligules lanceolate .... 

 Ligules short and truncate . 



6. Culm and sheath smooth, root creeping 

 Culm and sheath rough, root fibrous 



Avenaceum. 



. Borealii. 



Ccerulea. 



Crus-galli. 



Verticillata. 

 Viridis. 



2 



3 



Aquatica. 



Fluitans 

 4 

 6 

 Maritima. 



5 



Procumlem 



Rigida. 



Distam. 



Borreri. 



2 



7 

 Bullosa. 



3 

 Compressa. 



4 



5 



6 



Laxa. 

 Nemoralis. 

 Pratensis. 

 . Trimalii. 



