GEAMINEAE. 29 



Tribe VII. AVENEAE. 



Spikelets deciduous; lower flower perfect, upper staminate, awned; plant 



velvety. ■^'^- Holcus. 



Spikelets not deciduous; empty scales persistent, flowering ones deciduous. 

 Spikelets of 2 perfect flowers; rachilla not prolonged beyond the upper 



one. 36. Aira. 



Spikelets 2-many-flowered; racliilla prolonged beyond the upper flower. 

 Awn of flowering scale upon the back, inserted below the teeth. 

 Flowers all perfect, or the upper ones staminate or wanting. 

 Spikelets less than 12 mm. long; grain free, uufurrowed. 

 Flowering scale finely erose-dentate or 2-lobed. 



37. Desehampsia. 

 Flowering scale cleft or 2-toothed, with the teeth some- 

 times produced into awns. 38. Trisetum. 

 Spikelets over 12 mm. long; grain furrowed, usually ad- 

 herent to the scales. 39. Avena. 

 Upper flower perfect, lower staminate, its scales strongly 

 awned. 40. Arrhenatherum. 

 Awn from between the lobes or teeth of the flowering scale, gener- 

 ally twisted. 41. Danthonia. 



Tribe VIII. CHLOEIDEAE. 



One perfect flower in each spikelet. 

 No empty scales above the flower. 



Spikelets deciduous. 43. Spartiva. 



Spikelets not deciduous; empty scales persistent; low, slender 

 grasses. 42. Capriola. 



One to several empty scales above the flower. 



Spikelets scattered or remote on filiform spikes. 



44. Gymnopogon. 

 Spikelets crowded, sometimes 2-flowered. 45. Atheropogon. 



Two to three perfect flowers in each spikelet. 



Spikes with terminal spikelets. 46. Eleusive. 



Spikes without terminal spikelets, the rachis extending beyond them 

 into a point. 47. Dactyloctenium. 



Tribe IX. FESTUCEAE. 



Eachilla with long hairs enveloping the flowering scale; tall aquatic grass, 



48. Phragmites. 

 Eachilla and flowering scales naked or hairy, hairs much shorter than the 

 scales. 

 Flowering scale 1-3-nerved, or rarely with faint additional intermediate 

 nerves. 

 Lateral nerves of flowering scale pilose. 



Interuodes of the rachilla long, the deeply 2-lobed flowering 



scale attached by a long-pointed callus. 50. Triplasis. 

 Internodes of the rachilla and the callus of the flowering scale 

 short, blunt. 

 Panicle simple or compound, contracted or open, the spike- 

 lets on pedicels of varying length. 49. Tricuspis. 

 Panicle composed of long branches, along which the ap- 

 pressed spikelets are arranged on short pedicels. 



51. DipJachne. 

 Lateral nerves of the flowering scale glabrous. 



Second empty scale similar to the first. 52. Eragrostis. 

 Second empty scale very dissimilar to the first, broad and 

 rounded at the summit. 53. Eatonia. 



Flowering scales 5-many-nerved. 



Spikelets with 2 or more of the upper scales empty, broad and en- 

 folding each other. 54. Melica. 



