110 Bulletin V. 2. 



21. Grain closely enveloped by the fruiting glume which is 



firmer in texture than the empty ones. (Sub-tribe 6'//)>^^) 2 2 

 2T. Grain loosely or not at all enclosed by the hyaline or mem- 

 branaceous fruiting glumes, (Sub-tribes Phleoidece and 

 Euagrosteiz) ... 25 



22. Rachilla prolonged beyond the palea 20 Brachyelytrum. 



22. Rachilla not prolonged beyond the palea. ... 23 



23. Flowering glume with a trifid awn 17. Aristida. 



23. Flowering glume mucronate-pointed or with a simple awn. .24 



24. Awn twisted and geniculate 18. Stipa. 



24. Awn straight, sometimes reduced to a mucro . 



19. Muhlenbergia. 



25. Spikelets in a cylindrical, spike-like panicle, empty glumes 



ciliate along the keels 26 



25. Spikelets not in a cylindrical spike-like panicle, empty 



glumes not ciliate 27 



26. Empty glumes abruptly awn-pointed, persistent; palea pres- 



ent, flowering glumes awnless 21. Phleum. 



26. Empty glumes not awn-pointed, falling with the fruiting 



glume; palea none, flowering glume awned on the back. 

 (^See Fig. 48.) 22. Alopecurus. 



27. Flowering glume one-nerved, longer than the empty ones. 



23. Sporobolus. 



27. Flow^ering glume three to five-nerved, shorter than the empty 



ones 28 



28. Flowering glume raised on a distinct, naked internode of the 



rachilla; stamen one 24. Cinna. 



28. Flowering glume not raised on a distinct internode of the 



rachilla; stamens three 29 



29. Callus with long hairs (at least half as long as the flowering 



glume); rachilla continued beyond the palea 



26. Calamagrostis. 



29. Callus naked (or with a few very short hairs only); rachilla 



■ not prolonged behind the palea 25. Agrostis. 



30. Flowering glumes usually shorter than the empty ones, 



bearing a twisted or geniculate awn (some cultivated forms 

 excepted) on the back or between the teeth of the bifid 

 apex (Tribe Avene^.) ... 31 



30. Flowering glumes usually longer than the empty ones, 



awnless or bearing a (straight rarely bent) awn at or just 

 below the entire or two-toothed apex (Tribe FestucevE.) 44 



31. Flowering glumes thin and scarious, apex irregularly denti- 



culate, slender-awned on the back from near the base. 28. 



28. Deschampsia. 



31. Flowering glumes of firmer texture, entire, two-toothed or 



two-cleft at the apex 32 



32.. Spikelets strictly two-fiowered, one of the flowers staminate 33 



