22 POACEAE 



Tribe 4. ORYZEAE. 

 Spikelets perfect; empty glumes wanting or rarely rudimentary. 14. Homalocenchrus. 



Tribe 5. PHALARIDEAE. 

 Third and fourth glumes empty, awnless. 15. Ph.\laris. 



Third and fourth glumes enclosing staminate flowers. 16. Torresia. 



Tribe 6. AGROSTIDEAE. 

 Lemma indurate when mature and very closely embracing the grain, or at least firmer 

 than the empty glumes. 

 Spikelets all perfect, not in pairs. 



Lemma 3-awned. 17. Aristida. 



Lemma 1-awned or awnless. 



Awn twisted and bent. 18. Stipa. 



Awn not twisted. 



Lemma broad; awu deciduous. 



Inflorescence paniculate or racemiform. 19. Oryzopsis. 



Inflorescence dichotomous. 20. Eriocoma. 



Lemma narrow, glabrous or with short, appressed hairs; awn, if any, per- 

 sistent. 21. MtJHLENBERGIA. 

 Spikelets in pairs, one perfect and the other staminate or sterile, in a spike-like pan- 

 icle. 22. Ltcurus. 

 Lemma usually hyaline or membranaceous at maturity, at least more delicate than the 

 empty glumes. 

 Stigma sub-plumose (i. p., with short hairs all around), projecting from the ape.x of 

 the nearly closed glumes. 

 Inflorescence spike-like. 



RachiUa of the spikelets articulated above the empty glumes, which are there- 

 fore persistent. 23. Phleum. 

 RachiUa of the spikelets articulated below the empty glumes, hence the 

 spikelets falling off entire. 24. Alopecurus. 

 Inflorescence an open small panicle; dwarf arctic-alpine plant. 



25. Phippsia. 

 Stigma plumose, projecting from the sides of the spikelets; inflorescence an open or 

 spike-Uke panicle. 

 Grain not permanently enclosed in the lemma and palet; pericarp opening readily 

 at maturity. 

 Flowering glumes long-hairy on the veins. 26. Blepharoneuron. 



Flowering glumes not long-hairy on the veins. 27. Sporobolus. 



Grain permanently enclosed in the lemma and the palet; pericarp adherent. 

 Spikelets readily falling off when mature. 28. Polypogon. 



Spikelets with the empty scales at least persistent. 



Palet 1 -nerved and 1 -keeled; stamen 1. 29. Cinna. 



Palet 2-nerved and 2-keeled or sometimes wanting; stamens 3. 

 Lemma naked at the base. 30. Agrostis. 



Lemma with long hairs at the base. 



Flowering glume and palet thin-membranous. 31. Calamagrostis. 

 Flowering glume and palet chartaceous. 32. Calamovilfa. 



Tribe 7. AVENEAE. 

 Awn of the lemma inserted dorsally below the teeth. 

 Flowers all perfect or the upper staminate. 



Grain free, unfurrowed; spikelets less than 1 cm. long. 



Lemma erose-toothed or shortly 2-lobed at the apex. 33. Deschampsia. 

 Lemma 2-cleft or deeplv 2-toothed at the ape.ic; teeth awn-pointed. 



Awn twisted and bent. 34. Trisetum. 



Awn if present not twisted, straight. 35. Graphephorum. 



Grain furrowed, adherent to the glumes; spikelets exceeding 1 cm. in length. 



Ovary not crowned by a villous appendage. 36 Avena. 



Ovary crowned by a villous appendage (awned species of) 70. Bromus. 



Upper flowers perfect, the lower staminate. 37. Arrhenatherum. 



Awn of the lemma inserted between the teeth. 38. Danthonia. 



Tribe 8. CHLORIDEAE. 

 Plants with perfect flowers. 



Spikelets with 1 (rarely 2) perfect flowers. 



Spikelets deciduous as a whole; racliis articulated below the empty glumes. 

 Rachis produced above the upper spikelet; spikelets narrow. 



39. Spartina. 

 Rachis not produced above the upper spikelet; spikelets globose. 



40. Beckmannia. 

 Spikelets with at least the empty glumes persistent. 



Glumes above the perfect flower none; spikes digitate, very slender. 



41. Schedonnardus. 

 Glumes above the perfect flower 1 -several; spikes scattered. 



Spikes closely approximate, subverticillate. 42. Chixjris. 



Spikes scattered. 43. Bouteloua. 



Spikelets with 2-3 perfect flowers; spikelets alternate. 44. Leptochlo.\. 



Plants dioecious; spikelets of the two sexes very unlike. 45. Bulbilis. 



Tribe 9. FESTUCEAE. 

 Lemmas, at least of the pistillate spikelets, 3-lobed and 3-awned; plant dioecious. 



46. SC'LEROPOGO.\. 



