88 GRAMINEAE (GRASS FAMILY) 



H- ++ 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 cylindrical spike-like panicle ; bristles persistent. 



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



falling with Spikelets inclosed. 



SUBFAMILY II. POACOfDEAE 



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

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

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

 a manifest in tern ode of the rhachilla separates the florets, and is articulated below 

 them; spikelets more or less laterally compressed (except in MiUum}. The 

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

 poyon, Holcus, Sphenopholis, Spartina, and Becktnannia ; these are distin- 

 guished from SUBFAMILY I by the laterally compressed spikelets. 



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

 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. 



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



lea 1-keeled. 



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

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

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

 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, larger than the slightly indurated fertile 



lemma ; glumes very unequal. 



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



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



Tribe VI. AGROSTfDEAE. 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 (1-nerved in one species of Ciinm). 



* Lemma indurated. 

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



22. Milium. Spikelets dorsally compressed. 



i- +- Spikelets with a terminal awn ; margins of lemma not inrolled ; a callus at base. STII-INAK. 



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

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



-'.">. Aristida. A \vn,3-fld, the branches divaricate ; callus acute. 



* * Lemma membrannceous. 



- l.ciiiiiia awned from the tip or mucronute, closely infolding the grain : callus acute. 

 b .'f>. Muhlenbergia. IMiaohilla not prolonged behind the palea ; lemma pointed or awned. 



27. Brachyelytrum. l.'haehilla prolonged into a bristle behind the palea ; lemma long-awned. 



*- -i- Lemma awnless or dorsally awned, loosely embracing the grain. 

 M- Glumes eonspiciion^ly eompres-ed earinate ; spikelets in dense spike-like panicles. - I'm i N M ' 



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



cle partly included, ovoid. 



