88 GKAMINEAE (GRASS FAMILY) 



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



13. Echinochloa. Spikelets crowded in one-sided racemes, these arranged in a panicle. 



* * Spikelets with an involucre of bristles. 



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



15. Cenchrus. Spikelets (1-5 together) inclosed in a globular spiny bur-like involucre; this 



lulling with spikelets inclosed. 



Subfamily 11. POACOfDEAE 



Spikelets 1-raany-flowered, the imperfect or rudimentary floret, if any, usu- 

 ally uppermost, rhachilla iisually articulated above the glumes ichic/i are persist- 

 ent on the pedicel or rhachis after the fall of the florets; when 2-many-tiowe.red 

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

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

 spikeJets are articuhited below the glumes in Oryzeae, Alopecurus, Cinna, Poly- 

 pocfon, 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 h'^- 

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



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



below. 



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

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



ka 1-keeled. 



Tribe V PHALARIDEAE. Spikelets laterally compressed, 1 (rarely 8) -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 Ilierochloe ; 

 fertile lemma with a 1-2-nerved 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, lai-ger than the slightly indurated fertile 



lemma ; glumes very unequal. 



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



puiea and usually a staminate flower ; glumes subequal, scarcely exceeding the florets. 



Tribe VI. AGROSTIDEAE. Spikelets 1-flowered ; rhachilla sometimes prolonged behind tlie 

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

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

 * Lemma indurated. 

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



22. Milium Spikelets dorsally compressed. 



•*- -J- Spikelets with a terminal awn ; margins of lemma not inrolled ; a callus at base. — StipInax. 

 2:i. Oryzopsis. Awn simple, deciduous ; callus short, obtuse. 



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



25. Aristida. Awn 3-fid, the branches divaricate; callus acute. 



* * Lemma membranaceous, 

 •f- Lomma awned from the tip or mucronate, closely infolding the grain ; callus acute. 



26. Muhlenbergia. Rhachilla not prolonged behind the paloa ; lemma pointed or awned. 



27. Brachyelytrum. iniachilla prolonged into a bristle behind the palea , lemma long-awned. 



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

 *+ Glumes conspicuou.'ily compressed-carinate ; spikelets in dense spike-like panicles. — Pni.Eh'AE. 



23. Heleochloe. Lemma membranaceous like the glumes, awnless ; glumes not arislate ; pani- 



Ch' |) irtly included, ovoid. 



