9 6 GRAMINEAE. 



Flowering scale hyaline or membranous at maturity; empty scales coarser; grain loose. 



Spikelets in a dense spike-like panicle. (Some species of No. 31 may be looked for here. ) 

 Spikelets 3" or less long. 



Spikelets readily deciduous at maturity. 



Empty scales not awned. 29. Alopecurus. 



Empty scales awned. 3 2 - Polypogon. 



Spikelets not deciduous; empty scales persistent. 



Flowering scales slightly exceeding the empty ones. 27. Heleochloa. 



Flowering scales much shorter than the empty ones. 28. Phleum. 



Spikelets 5" -6" long; tall seashore grasses. 37. Ammophila. 



Spikelets variously panicled; panicle not spike-like, except in a few species of No. 31. 

 Seed loosely enclosed in the pericarp, which opens readily at maturity. 



Empty scales minute ; low arctic grass. 30. Phippsia. 



Empty scales not minute; no callus, awns or hairs. 31. Sporobolus. 



Seed adherent to the pericarp. 



Palet i -nerved; stamen i; flower plainly stalked: scales not hairy. 34. Cinna. 

 Palet 2-nerved; stamens 3; flower not plainly stalked. 



Flowering scale bifid, with a delicate awn on its back; rachilla prolonged into a 



short bristle. 39- Apera. 



Flowering scale entire; rachilla not prolonged into a bristle. 



Callus with a tuft of long hairs at the base (except in species of genus 36). 

 Rachilla extended beyond the palet. 36. Calamagrostis. 



Rachilla not extended beyond the palet. 38. Calamovilfa. 



Callus naked, or with very short hairs. 



Empty scales somewhat shorter than the flowering ones; arctic grass. 



33. Arctagrostis. 



Empty scales longer than the flowering ones; panicle open; Spikelets small. 



35. Agrostis. 



Tribe VIII. AVENEAE. 



Spikelets deciduous; lower flower perfect, upper staminate, awned; plant velvety. 40. Holcus. 

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



Spikelets of 2 perfect flowers; rachilla not prolonged beyond the upper one. 41. Aira. 

 Spikelets 2-many-flowered; rachilla 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 6" long; grain free, unfurrowed. 



Flowering scale finely erose-dentate or 2-lobed. 42. Deschampsia. 



Flowering scale cleft or 2-toothed, with the teeth sometimes produced into 



awns. 43. Trisetum. 



Spikelets over 6" long; grain furrowed, usually adherent to the scales. 



44. A vena. 



Upper flower perfect, lower staminate, its scale strongly awned. 45. Arrhenatherum. 

 Awn from between the lobes or teeth of the flowering scale, generally twisted. 



46. Danthonia. 



Tribe IX. CHLORIDEAE. 



Flowers perfect or some of them rudimentary. 



i perfect flower in each spikelet; sometimes 2 in Nos. 53 and 54.- 

 No empty scales above the flower. 

 Spikelets deciduous. 



Rachis produced beyond the upper spikelet; Spikelets narrow. 48. Spartina. 

 Rachis not so produced; Spikelets globose, sometimes 2-flowered. 54. Beckmannia. 

 Spikelets not deciduous; empty scales persistent; low slender grasses. 



Spikes 2-6, slender, digitate, i'-a' long. 47. Capriola. 



Spikes many along a common axis, 2' -4' long. 52. Schedonnardus. 



One-several empty scales above the flower. 



Lower empty scales 4; spike solitary, dense. 49. Campulosus. 



Lower empty scales 2. 



Spi kes in false whorls or closely approximate ; scales long-awned. 50. Chloris. 

 Spikes remote, or the lowest only approximate. 



Spikelets scattered or remote on filiform spikes. 51. Gymnopogon. 



Spikelets crowded, sometimes 2-flowered. 5-5 Bouteloua. 



7-3 perfect flowers in each spikelet. 



Spikelets densely crowded; spikes usually digitate. 



.Spikes with terminal Spikelets. . Eleusine. 



Spikes without terminal spikelets, the rachis extending beyond them into a point. 



56. Dactyloctenium. 



Spikelets distinctly alternating; spikes remote. 57 Leptochloa. 



Spikelets dioecious, very unlike; spikes short; low prairie grass. 58. Bulbilis. 



Tribe X. FESTUCEAE. 



Rachilla with long hairs enveloping the flowering scale; tall aquatic grass. 60. Phragmiies. 



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



Stigmas barbellate; spikelets in clusters of 3-6 in the axils of stiff spinescent leaves. 



Stigmas plumose; spikelets not in the axils of leaves; inflorescence various 5 



Sptkelets of two forms, the fertile i-3-flowered, surrounded by the sterile, consisting of 



76- Cynosnrns. 



Flowering scale 2-vtoothed or pointed, usually 3-nerved; lateral nerves and callus 



' an enluvemettt of the rachilla just below the flowering scale) generally hairy. 

 Spikelets with .; many fertile flowers. 61. 5/V-/;c/J 



Spikelets i-3-flowered ; flowering scales keeled ; branches of the diffuse panicle 

 long and capillary. 62 RgdeBia. 



