234 



COMPARATIVE ANALYSIS. 



2. Leaves auricled, glabrous . . . Giganteus. 

 Leaves not auricled, mostly pubescent . . 3 



3. Awn much longer than florets . . . .4 

 Awn not much longer than florets . . 5 



4. Panicle erect in flower, awn twice as long as the florets Maximus. 

 Panicle drooping, awn not twice as long as the florets . Sterilis. 



5. Florets pubescent . . . . .6 

 Florets glabrous ..... 8 



6. Florets about eight, remote, and longer than the awn . Asper. 

 Florets nine or more, crowded, as long as the awn . 7 



7. Leaves slightly hairy, panicle spreading . . Velutinus. 

 Leaves very pubescent, panicle erect, close . . Mollis. 



8. Panicle drooping in fruit . . . .9 

 Panicle erect . . . . . 11 



9. Spikelets lanceolate, awns straight . . Arven&is. 

 Spikelets ovate, awns not straight . . . 10 



10. Awns remarkably spreading, leaves pubescent . Squarrosum. 

 Awns not spreading, leaves slightly hairy . . Secalinm. 



11. Root leaves much narrower than the cauline . . Erectus. 

 Root leaves not narrower than the cauline . . Racemosus. 



AVENA. 



1. Spikelets drooping, florets not larger than the calyx . . 2 

 Spikelets erect, florets mostly longer than the calyx . 3 



2. Florets terminated by two bristles . . . Strigosa. 

 Florets not terminated by two bristles . . . Fatua. 



3. Glumes very urtequal .' F laves cms. 

 Glumes nearly equal . . . .4 



4. Leaves downy, spikelets two or three-flowered . Pulescens. 

 Leaves not downy, spikelets more than three-flowered . 5 



5. Lower leaves involute .... Pratensu. 

 Leaves flat ..... 6 



6. Sheaths flat, lower part of culm two-edged . . Planiculmis. 

 Sheaths round, culm round .... Alpina. 



AETTNDO. 



Florets purplish, culm five feet high . . . Phragmites. 



ELTMUS. 

 I Leaves flat, florets awned .... Europceus. 



Leaves involute, florets awnless . . . .2 



2. Spike drooping, glumes longer than the florets . Geniculatus. 



Spike erect, glumes not longer than the florets . Arenarius. 



HOBDETJM. 



1. Glumes all setaceous 



Prateme. 



