58 Kakl M. Wiegand and Arthur J. Eames 



d. Floret sessile ; spikelet disarticulating between empty and flowering glumes ; 

 palet 2-nerved ; stamens 3. 

 c . Callus long-hairy ; rhachilla prolonged behind the palet. 



22. Calamagrostis 

 c. Callus glabrous ; rhachilla not prolonged. 



/. Flowering glume shorter than the empty glumes and thinner, obtuse, 



3-nerved. 23. Agrostis 



/. Flowering glume equaling or exceeding the empty glumes and of the 

 same texture, acute, 1-nerved. 25. Sporobolus 



d. Floret stipitate ; spikelet disarticulating below the empty glumes ; palet 

 1(2) -nerved; stamen 1. 24. Cinna 



c. Empty glumes very much compressed, almost wing-carinate ; spikelets in very 

 dense spike-like panicles. 

 d. Empty glumes not aristate ; flowering glume awned below the middle. 



26. Alopecurus 

 d. Empty glumes aristate; flowering glume awnless. 27. Phleum 



b. Rootstocks short, often branched, very scaly and knotty ; flowering glume awned 

 at the tip, or awnless. 

 c. Rhachilla not prolonged behind the palet ; callus and rhachilla hairs more or 

 less developed ; culms usually branching above ; leaves not broad. 



28. MUHLENBERGIA 



c. Rhachilla prolonged ; callus and rhachilla hairs wanting ; culms not branching 

 above; leaves very broad, lanceolate. 29. Dilepyrum 



a. Flowering glumes thicker and firmer than the empty glumes ; spikelets dorsally 

 compressed or terete. 

 b. Spikelets awnless, dorsally compressed ; flowering glume without a callus, the 



margins inrolled. 30. Milium 



b. Spikelets awned, subterete ; flowering glume with a callus, the margins not 

 inrolled. 31. Oryzopsis 



Tribe 5. Chlnridcae 



a. Spikelets 3-6-flowered. 32. Eleusine 



a. Spikelets 1-flowered. 



b. Empty glumes broad, equal; spikelets orbicular. [Beckmaxxia] 



b. Empty glumes narrow, unequal ; spikelets ovate-lanceolate. 33. Spartina 



Tribe 6. Phalarideae 

 a. Sterile flowering glumes not reduced. 



b. These glumes staminatc and awnless ; empty glumes subequal. 



34. HiEROcHLoii 

 b. These glumes empty and dorsally awned ; empty glumes very unequal. 



35. Anthoxanthum 

 a. Sterile flowering glumes much reduced, awnless; empty glumes equal. 



36. Phalaris 



Tribe 7. Oryccac 

 One genus. 37. Leersia 



Tribe 8. Zizanieae 

 One genus. • 38. Zizania 



Tribe 9. Paniceac 

 a. Spikelets without an involucre. 



b. Second flowering glume chartaceous, with hyaline flat margins; inflorescence 



of digitate spike-like branches. 39. Digitaria 



b. Second flowering glume thicker, with firm inrolled margins. 



c. Branches of the inflorescence more or less 1 -sided and spike-like. 



