GRASS FAMILY 105 



Tribe I\'. Orvzeae. 



A single genus. 12. Hoinalocenchrits. 



Tribe \'. Phalarideae. 



Lateral florets staminate; spikelets brown and shining. 15. Torresia. 



Lateral florets neuter; spikelets green or yellowish. 



Lateral florets reduced to small avvnless bracts; spikelets much compressed laterally. 



13. Phalaris. 

 Lateral florets consisting of awned hairy sterile lemmas about as long as the fertile floret; spikelets 

 terete. H- Antlioxauthum. 



Tribe VL Agrostideae. 



Glumes wanting; a low annual. 23. Coleantlius. 



Glumes present. 



Rachilla articulate below the glumes, these falling with the spikelet. 



Glumes long-awned. 26. Polypogon. 



Glumes awnless. 



Rachilla not prolonged behind the palea; panicle dense and spike-like. 22. Alopeciiriis. 

 Rachilla prolonged behind the palea; panicle open. 27. Cinna. 



Rachilla articulate above the glumes. 



truit indurate, terete, awned, the nerves obscure; callus usually well-developed, oblique, bearded. 

 Awn trihd, the lateral divisions sometimes short, rarely obsolete (when obsolete no line of 



demarcation between awn and lemma). 16. Aristida. 



Awn simple, a line of demarcation between the awn and lemma. 



Awn persistent, twisted, bent, several to many times longer than the slender fruit; callus 



sharp-pointed. 17. Stipa. 



Awn deciduous, not twisted, sometimes bent, rarely more than 3 or 4 times as long as the 

 plump fruit; callus short, usually obsolete. 18. Orysopsis. 



Fruit thin or firm but scarcely indurate, if firm the nerves prominent or evident; callus not well- 

 developed. 

 Glumes longer than the lemma (equaling it only in Agrostis aeqnivaliis and A. thurbcriaiia). 

 Panicle feathery, capitate, nearly as broad as long; spikelets woolly. 32. Lagurus. 

 Panicle not feathery; spikelets not woolly. 



Glumes compressed-carinate, abruptly mucronate, stiffly ciliate on the keels; panicle dense, 



cylindric or ellipsoid. 21. Phleuin. 



Ghmies not compressed-carinate, not ciliate. 



Glumes saccate at base; lemma long-awned; panicle contracted, shining. 



29. Gastridiiim. 

 Glumes not saccate at base; lemma awned or awnless; panicles open or contracted. 



Florets with hairs at base half as long as the lemma; palea present. 



30. Calamagrostis. 

 Florets naked at base or with short hairs (hairs longer in A. hatlii with obsolete 



, iialea). 28. Agrostis. 



Glumes not longer than the lemma, usually shorter (the awn tips longer in Muhlenbcrgia 

 raccinosa) . 

 Lemma awned from the tip or mucronate; 3-5-nerved (lateral nerves obsolete in M. repens). 



19. Muhlenbergia. 

 Lemma awnless or awned from the back. 



Lemma bearing a tuft of hairs at the base from the short callus. 31. Ammophila. 

 Lemmas without hairs at base. 



Fruit at maturity falling from the lemma and palea; seed loose in the pericarp, this 

 usually opening when ripe. 

 Inflorescence cai)itate in the axils of broad bracts. 20. Crypsis. 



Inflorescence an open or contracted panicle. 24. Sporobohis. 



Fruit not falling from the lemma and palea, remaining permanently inclosed in them; 

 seed adnate to the pericarp; panicles spike-like. 25. Epicampes. 



Tribe \TI. Avexeae. 



Spikelets awnless or the upper lemma mucronate. (See Trisetum wolfii.) 



Articulation below the glumes; glumes distinctlv different in shape, the second widened above. 



37. Sphettopholis. 

 Articulation above the glumes; glumes not much dissimilar in shape. 38. Koeleria. 



Spikelets awned. 



Florets 2, one perfect, the other staminate. 



Lower floret staminate, the awn twisted, geniculate, exserted. 40. Arrheiiatlierum. 



Lower floret fertile, awnless; awn of upper floret hooked. 33. Notlwlcits. 



Florets 2 or more, all alike except the reduced upper ones. 



Awn arising from between the teeth of a bifid apex, flattened, twisted; inflorescence a snnple 



panicle or reduced to a raceme or even to a single spikelet. 41. Danthoiiia. 



Awn dorsal, not flattened; lemma often bifid at apex. 



Spikelets large, the glumes over 1 cm. long. 39. A'cena. 



Spikelets less than 1 cm. long. 



Lemmas keeled, bidentate, awned from above the middle. 36. Trisetum. 



Lemmas convex, awned from below the middle. 



Apex of lemma acuminate, bidentate; rachilla not prolonged behind the upper floret. 



35. Aspris. 

 Apex of lemma broad, erose; rachilla prolonged behind the upper floret. 



54. Aira. 



Tribe VIIT. Chlorideae. 



Spikelets with more than 1 perfect floret. 



Spikes numerous, slender, along an elongate a.xis. 48. Lcptochloa. 



Spikes few, thick, digitate or nearly so. 47. Eleusiue. 



Spikelets with only 1 perfect floret, often with additional imperfect florets above. 

 Spikelets witho'ut additional modified florets, the rachilla sometimes prolonged. 

 Rachilla articulate below the glumes. 



Glumes unequal, narrow. 43. Spa'tiita. 



Glumes equal, broad and boat-shaped. 46. Beckmanma. 



Rachilla articulate above the glumes; spikes digitate; rachilla prolonged. ^2. Capnola. 



Spikelets with one or more sterile florets above the perfect one. 



Spikes digitate or nearly so. 44. Chloris. 



Spikes racemose along the main axis. 45. Bouteloua. 



