88 GBAMINEAE (GRASS FAMILY) 



*-*■ -H- Sterile lemma awned or pointed ; fruit acuminate ; palea not included at the summit, 

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

 * * Spikelets with an Involucre of bristles. 



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



15. Cenchrus. Spikelets (1-5 together) inclosed In a globular spiny bur-like Involucre; ihu 



falling with spikelets inclosed. 



Subfamily II. POACOfDEAE 



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

 ftliy uppermost, rhachiUa usually articulated above the glumes which, are persist- 

 ent on the pedicel or rhachis after the fall of the florets; when 2-m any-flowered 

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

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

 spikelets are articulated below the glumes in Ot^zeae^ Alopecurus, Cinna^ Poly- 

 pogon^ Holcus, Sphenopholis^ Spartina, and Beckmannia; these are di8tin> 

 guished from Subfamily I by the laterally compressed spikelets. 



Tribe IV. OR'tZEAE. 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 pistifiate above, staminatfl 



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 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 stamlnate flower in HieroclUoe; 

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



19. Phalaxis. 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. 

 2t. Hierochloe. Sterile lemmas larger than the fertile lemma, indurated, Inclosing a 2-nerved 

 palea and usually a stamlnate flower ; glumes subequal, scarcely exceeding the florets. 



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

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

 lemma ; palea 2-nerved, rarely nerveless or wanting (l-nerved in one species of Oinna), 

 * Lemma indurated. 

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



22. Milium. Spikelets dorsally compressed. 



■I- -I- Spikelets with a terminal awn ; margins of lemma not inrolled ; a callus at boae. — StipInak 



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, closely infolding the gi*alu ; callus ocuto. 



26. Mublenbergia. Ehacbilla not prolonged behind the palea ; lemma pointed or awned. 



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



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

 ** Glumes conspicuously compressed-carlnate ; spikelets in dei^se spike-like panicles. — PhleInae. 

 '28. Heleochloe. Lemma ineinbranaceous like the glumes, awnless ; glumes not artstate ; nanj 

 cle partly included, ovoid. 



