p.21

415

10. Flowers, naked, with one stamen ... 9-Cinna
10. Flowers hairy, stamens three ... 12-Calamagrostis
11. Stamens three ... 10-Muhlenbergia
11. Stamens two ... 11-Brachyclytrum
12. Glumes two ... 13
12. Glumes none, leaves retrorsely scabrous ... 1-Leersia
13. Paleae membranaceous ... 14
13. Paleae coriaceous ... 48-Milium
14. Fruit coated ... 15
14. Fruit naked ... 7-Sporobolus
15. Flowers stalked ... 8-Agrostis
15. Flowers sessile ... 6-Vilfa
16. Flowers awned ... 17
16. Flowers without awns ... 22
17. Spikes solitary ... 18
17. Spikes numerous not bearded, unilateral paleae cartilaginous ... 50-Panicum
17. Spikes two or more polygamous, sterile flowers, bearded ... 55-Andropogon
18. Spikes simple, or nearly so ... 19
18. Spikes paniculate, or lobed ... 21
19. Involuere none ... 20
19. Involuere of two or more bristles ... 51-Setaria
19. Involuere burr-like ... 52-Cenchrus
20. Paleae with awns one to three times their length ... 4-Alopecurus
20. Paleae with awns five times their length ... 37-Hordeum
21. Both glumes and paleae awned ... 10-Muhlenbergia
21. Glumes awnless, paleae awned ... 46-Anthoxanthum
22. Flowers perfect or polygamous ... 23
22. Spikes monoecious ... 25
23. Spikes one-sided ... 24
23. Spikes cylindrical, solitary terminal... 5-Phleum
24. Spikes two or more, spikelets suborbicular ... 49-Paspalum
24. Spikes digitate or verticillate, linear ... 50-Panicum
24. Spikes pedunculate, in a two-sided panicle ... 16-Spartina
24. Spikes sessile, in a one-sided panicle ... 3-Lepturus
25. Spikes all terminal, sterile above, fertile at base ... 54-Tripsacum
25. Fertile spikes lateral, sterile ones terminal panicled ... 53-Zea
26. Inflorescence in panicles ... 27
26. Inflorescence in spikes ... 39
27. Flowers awned ... 28
27. Flowers without awns ... 33
28. Lower palea awned on the back ... 29
28. Lower palea awned on the apex ... 32
29. Awn near the base of the palea ... 30
29. Awn near the apex of the palea ... 31