GRASS FAMILY 85 



Glumes not conspicuously compressed. 



Pericarp loosely enclosing the seed; inflorescence an open panicle. .20. SPOROBOLUS. 

 Pericarp adherent to the seed; inflorescence open or contracted. 



Glumes long-awned 22. POLYPOGON. 



Glumes awnless, or short-awned. 



Inflorescence a long slender dense spike-like panicle 21. EPICAMPBS. 



Inflorescence often contracted but not conspicuously elongated. 



Palea 1-nerved, or apparently so 23. CINNA. 



Palea plainly 2-nerved (sometimes nerveless or wanting). 



Glumes plumose-ciliate ; inflorescence an ovoid head 28. LAGURUS. 



Glumes not plumose. 



Glumes saccate at base, much longer than the lemmas . . 25. GASTBIDIUM. 

 Glumes not saccate at base. 



Eachilla not prolonged behind the palea (except in A. thurberiana) ; 

 callus hairs short or none (except in A. hallii) . . . .24. AGEOSTIS. 

 Rachilla prolonged behind the palea as a usually hairy bristle. 



Lemma awned from the back ; callus hairs long 



26. CALAMAGEOSTIS. 



Lemma awnless; callus hairs short 27. AMMOPHILA. 



Tribe VI. Aveneae. Spikelets 2 to several-flowered, in open or contracted panicles; rachilla 

 prolonged behind the uppermost floret (except in Aira) ; glumes usually longer than the 

 first floret; 1 or more of the lemmas awned on the back or from the teeth of the bifid 

 apex (usually awnless in Koeleria and Sphenopholis) ; callus and usually the rachilla 

 joints hairy. 



Eachilla not prolonged; spikelets 2-flowered, perfect 30. AIRA. 



Bachilla prolonged behind the uppermost floret; spikelets 2 to several-flowered. 



Articulation below the glumes, the spikelets falling entire or the glumes and lowest 

 florets together. 



Glumes much exceeding the 2 florets; spikelet awned 29. NOTHOLCUS. 



Glumes exceeded by the upper floret; spikelet awnless 33. SPHENOPHOLIS. 



Articulation above the glumes. 



Awns wanting or but a mucronate tip 34. KOELERIA. 



Awns present. 



Awns from between the teeth of the bidentate apex of the lemma, flattened, twisted. 



36. DANTHONIA. 

 Awns dorsal, not flattened. 



Lemmas more than % inch long 35. AVENA. 



Lemmas less than y 2 inch long. 



Lemmas keeled; awn from above the middle 32. TRISETTJM. 



Lemmas convex; awn from below the middle 31. DESCHAMPSIA. 



Tribe VII. Chlorideae. Spikelets 1 to several-flowered, sessile in 1-sided spikes; spikes, 

 digitate or racemose; lemma awnless or awned from between teeth; spikelets usually 

 compressed and closely imbricated (more distant and often slightly pediceled in Lep- 

 tochloa) . 

 Spikes digitate. 



Plants perennial, extensively creeping 37. CYNODON. 



Plants annual, more or less spreading but not creeping. 



Perfect florets 2 or more, awnless 42. ELEUSINE. 



Perfect floret 1 (long-awned) 39. CHLORIS. 



Spikes racemose. 

 Spikelets 1-flowered. 



Glumes narrow, unequal 38. SPARTINA. 



Glumes broad, boat-shaped, equal 41. BECKMANNIA. 



Spikelets with more than 1 floret. 



Lemmas 3-awned; spikelets imbricated, with only 1 perfect floret 40. BOUTELOUA. 



Lemmas 1 -awned or awnless; spikele*ts somewhat distant, with 3 to several perfect 



florets 43. LEPTOCHLOA. 



Tribe VIII. Festuceae. Spikelets 2 to many-flowered, pedicellate in racemes or in open or 

 contracted panicles (spikes in Orcuttia; solitary in Monanthochloe) ; glumes usually 



