WOOTON AND STANDLEY PLOEA OF NEW MEXICO. 45 



Spikelets oval or obovate; fruit chartaceous, 

 rigid, the lemma margins inrolled, not 

 hyaline. 

 First glume present; spikelets panicled, 



rarely in racemes 17. Panicum (p. 56). 



First glume obsolete; spikelets in racemes. 

 Spikelet with a swollen ringlike cal- 

 lus below; fruit awn-tipped... 15. Eriochloa (p. 54). 

 Spikelets without a callus; fruit not 



awned 16. Paspalum (p. 55). 



Tribe V. PHALAKIDEAE. 



Panicles dense and contracted; sterile lemmas minute. 21. Phalaris (p. 61). 

 Panicles loose and open; sterile lemmas inclosing 



staminate flowers 22. Savastana (p. 61). 



Tribe VI. AGROSTIDEAE. 



Lemmas indurated at maturity, closely inclosing the 

 grain . 

 Spikelets in pairs, one perfect, the other staminate 



or sterile (in spikelike panicles) 23. Lycurus (p. 62). 



Spikelets not in pairs, all perfect. 



Lemma 3-awned (2 of the awns sometimes very 



small) 24. Aristida (p. 62). 



Lemmas 1-awned or awnless. 



Awns twisted and bent 25. Stipa (p. 65). 



Awns not twisted, or wanting. 



Lemmas narrow ; awns, when present, 



persistent 26. Muhlenbergia (p. 68). 



Lemmas broad; awns deciduous 27. Oryzopsis (p. 72). 



Lemmas usually thin at maturity, at least more delicate 

 than the glumes; grain loosely inclosed. 

 Glumes conspicuously compressed-keeled; panicle 

 dense and spikclike, cylindrical. 

 Rachilla jointed above the glumes, these per- 

 sistent; lemma awnless 28. Phleum (p. 73). 



Rachilla jointed below the glumes, these fall- 

 ing with the spikelets; lemma awned. .29. Alopecurus (p. 73). 

 Glumes not compressed-keeled; panicles mostly 

 open and spreading, rarely crowded and 

 spikclike. 

 Panicle spikelike, elongated, 30 cm. long or 



more 30. Epicamfi s (p. i 



Panicle not elongated. 



Spikelets articulated below the glumes; 

 falling entire. 



Glumes awned; panicles dense S3. Polypooon i]>. 77). 



Glumes awnless; panicles open 34. < iw\ (p 



Spikelets articulated above the glumes, 

 these persistent after the fall of the 

 florete. 



