88 GRAMINEAE (GRASS FAMILY) 



++ ++ Sterile lemma awned or pointed ; fruit acuminate ; palea not included at the summit. 



13. Echlnochloa. Spikelets crowded in one-sided racemes, these arranged in a psniclfl. 



* * Spikelets with an involucre of bristles. 



14. Setaria. Spikelets in a dense cylindrical spike-like panicle ; bristles persistent. 



15. Cenchrus. Spikelets (1-5 tog-ether) inclosed in a globular spiny bur-like involucre; thii 



falling with spikelets inclosed. 



Subfamily II. POACOfDEAE 



Spikelets l-many-flowered, the imperfect or rudimentary floret, if any, usu- 

 Aliy uppermost, rhachilla usually articulated above the glumes which are persist- 

 ent on the pedicel or rhachis after the fall of the florets ; when 2-many-flowerfcd 

 a manifest internode of the rhachilla separates the florets, and is articulated below 

 tbem; spikelets more or less laterally compressed (except in Milium). The 

 spikelets are articulated below the glumes in Oryzeae, Alopecurus, Cinna, Poly- 

 pogon, Holcus, Sphenopholis, Spartina, and Beckmannia ; these are distin- 

 guished from Subfamily I by the laterally compressed spikelets. 



Tribe IV. ORYZEAE. Spikelets unisexual or perfect, in loose panicles ; rhachilla articulated be- 

 low the glumes ; glumes often wanting ; stamens often 6. 



16. Zizanla. Spikelets unisexual, unlike in appearance ; panicle pistillate above, staminate 



below. 



17. Zizaniopsis. Spikelets unisexual, much alike in appearance, intermixed in the same panicle. 



18. Leersia. Flowers perfect, spikelets much flattened laterally ; lemma carinate, awnless ; pa- 



lea 1-keeled. 



Tribe V. PHALARIdEAE. Spikelets laterally compressed, 1 (rarely 3) -flowered ; two sterile 

 lemmas below the fertile floret, and falling attached to it, usually empty and unlike the fertile 

 lemma, sometimes reduced to bristles, or sometimes with a staminate flower in Ilier ochloe ; 

 fertile lemma with a 1-2-iierved or nerveless palea and a perfect flower. 



19. Phalaris. Sterile lemmas very narrow, much shorter than the indurated fertile lemma, 



which is much exceeded by the equal glumes. 



20. Anthoxanthum. Sterile lemmas dorsally awned, larger than the slightly indurated fertile 



lemma ; glumes very unequal. 



21. Hierochloe. Sterile lemmas larger than the fertile lemma, indurated, inclosing a 2-nerved 



palea and usually a staminate flower ; glumes subequal, scarcelj' exceeding the florets. 



Tribe VI. AGROSTIdEAE. Spikelets 1-flowered ; rhachilla sometimes prolonged behind the 

 palea into a naked or plumose bristle ; glumes subequal, usually equahng or exceeding the 

 lemma ; palea 2-nerved, rarely nerveless or wanting (1-nerved in one species of Cinna). 



* Lemma indurated. 



+■ Spikelets awnless ; callus none ; margins of lemma inrolled. 



22. Milium. Spikelets dorsally compressed. 



•t- -I- Spikelets with a terminal awn ; margins of lemma not inrolled ; a callus at base. — STipiNAE 



23. Oryzopsis. Awn simple, deciduous ; callus short, obtuse. 



24. Stipa. Awn simple, persistent ; callus usually acute. 



25. Aristida. Awn 8-fid, the branches divaricate ; callus acute. 



* * Lemma membranaceous. 

 +- Lemma awned from the tip or mucronate, clo.sely infolding the grain ; callus acute. 



26. Muhlenbergia. nbaohilla not prolonged behind the palea ; lemma pointed or awned. 



27. Brachyelytrum. Khachilla prolonged into a bristle behind the palea ; lemma long-awned. 



-t- +- Lemma awnless or dorsally awned, loosely embracing the grain. 

 ♦* Glumes conspicuously com pressed -carinate ; spikelets in dense spike-like panicles. — Phi.e1n.\e. 



28. Heleochloe. Lemma membranaceous like the glumes, awnless ; glumes not aristate ; pani 



cle partly included, ovoid. 



