The Grassks ok Tennksskk. 9 



II. Spikelets surrounded by an involucre consisting of one to 

 many bristles, which are sometimes grown together be- 

 coming bur-like 12 



11. Spikelets not surrounded by bristles or special covering 



9. Panicum. 



12. Bristles persistent 10. Setaria. 



12. Bristles falling with the spikelets 13 



13. Bristles grown together at the base, forming a bur-like cov- 



ering over the spikelets 11. Cenchi'us 



13. Bristles distinct 12. Pennisetum 



14. Spikelets unisexual, monoecious, linear, the awned pistil- 



late above and the staoainate below in the same inflor- 

 escence 13. Zizania. 



14. wSpikelets all hermaphrodite 15 



15. Empty glumes two, small 14. Oryza. 



15. Empty glumes none 15. Leersia. 



16. Culms perennial, woody, leaf-blade articulated with the 



sheath (Tribe Bambuse.^.) 65. Arundinaria. 



16. Culms annual, herbaceous, leaf-blade continuous witli the 



sheath 17 



17. Spikelets distinctly pedicellate, in racemes or panicles 



(these sometimes spike-like) 18 



17. Spikelets sessile, in true spikes, (sometimes on very short 



pedicels and then in one-sided or unilateral racemes) . . 36 



18. Spikelets one-tiowered 19 



18. Spikelets two to many-flowered 30 



19. Empty glumes four, the third and fourth very unlike the 



first and second and falling with the fruiting glume 

 (Tribe Phalaride.i-:) 20 



19. Empty glumes two 21 



20. Third and fourth glumes reduced to narrow scales or 



bristles, awnless 16. Phalaris. 



20. Third and fourth glumes smaller than the first and second, 



aw^ned 17. Anthoxanthum. 



21. Grain closely enveloped by the fruiting glume, which is 



firmer in texture than the empty ones. (Sub-tribe Stipecc) 22 



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



branaceous fruiting glumes. (Sub-tribes P/iIeoideiv and 

 £uagrostecr) 2^ 



22. Rachilla prolonged beyond the palea . 21. Brachyelytrum. 



22. Rachilla not prolonged beyond the palea 23 



2^. Flowering glume with a trifid awn .... 18. Aristida. 



23. Flowering glume muc^onate-pointed or with a simple awn 24 



24. Awn twisted and geniculate 19. Stipa 



24. Awn straight, sometimes reduced to a mucro 



20. Muhlenbergia. 



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



ciliate along the keels 26 



25. Spikelets in open or contracted panicles, empty glumes not 



ciliate 27 



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



ent, flowering glumes awnless 22. Phleum. 



