14. Pedicel not thickened (if slightly so the spikelets awned), neither appressed 



nor adnate to the rachis joint, this usually slender; spikelets usually 

 awned (15) 



15(14). Fertile spikelet with a hairy-pointed caHus, formed of the attached sup- 

 porting rachis joint or pedicel; awns strong 58. Andropogon 



15. Fertile spikelet without a callus, the rachis disarticulating immediately below 



the spikelet; awns slender 59. Sorghum 



16(1). Culms woody, perennial; leaf blades articulated with sheaths 



1. Arundinaria 



16. Culms herbaceous, annual (somewhat woody and persistent in Arundo); leaf 



blades and sheaths continuous (17) 



17(16). Spikelets with 2 (rarely 1) staminate, neuter or rudimentary lemmas 

 unlike and below the fertile lemma; no sterile nor rudimentary 

 floret above (18) 



17. Spikelets without sterile lemmas below the perfect floret (19) 



18(17). Lower florets staminate; spikelets brown, shining 40. Hierochloe 



18. Lower florets neuter; spikelet green or yellov/ish 41. Phalaris 



19(17). Spikelets unisexual, falling entire, 1-flowered, terete or nearly so (20) 



19. Spikelets perfect (rarely unisexual but then not as above), usually articulate 



above the glumes (22) 



20(19). Culms slender; floating aquatic; staminate and pistillate spikelets borne 

 in separate inflorescences 46. Hydrochloa 



20. Culms robust; plants tall, usually standing in water; staminate and pistillate 



spikelets borne in the same panicle (21) 



21(20). Pistillate spikelets on the ascending upper branches, the staminate on 

 the spreading lower branches of the panicle; annual or perennial.... 

 44. Zizania 



21. Pistillate spikelets at the ends, the staminate below on the same branches 



of the panicle; perennial 45. Zizaniopsis 



22(19). Spikelets articulate below the glumes, 1-flowered, very flat, the lemma 

 and palea about equal, both keeled; glumes small or wanting (23) 



22. Spikelets articulate above the glumes (rarely below, but at least one of the 



glumes well-developed) (24) 



23(22). Glumes minute; lemma often awned 42. Oryza 



23. Glumes wanting; lemma awnless 43. Leersia 



1A{T1). Spikelets sessile on a usually continuous rachis (short-pedicellate in 

 Leptochloa; the rachis disarticulating in Hordeum) (25) 



24. Spikelets pedicellate in open or contracted sometimes spikelike panicles, rarely 



racemes (34) 



25(24). Spikelets on opposite sides of the rachis; spike terminal, solitary (26) 



25. Spikelets on one side of the rachis; spikes usually more than 1, digitate or 



racemose (30) 



26(25). Spikelets solitary at each node of the rachis (rarely 2 in species of 

 Agropyron, but never throughout) (27) 



26. Spikelets more than 1 at each node of the rachis (solitary in part of the spike 



in some species of Ely mux) (29) 



27(26). Spikelets 1-flowered, sunken in hollows of the rachis; spikes slender, 

 cylindric; low annuals 20 Parapholis 



27. Spikelets 2- to several-flowered, not sunken in the rachis (28) 



171 



