POACEAE. 



11 



Flowering scales cleft or 2-toothed, the 

 teeth extending into awns. 

 Grain furrowed, adherent to the scale : spikelets 

 exceeding 1 cm. in length. 

 Flowers various, the upper perfect, the lower stami- 

 nate and with the scale strongly awned. 

 Flowering scales awned between their usually awned 

 teeth. 



Tribe VIII. CHLORIDEAE. 



Spikelets deciduous as a whole. 



Spikelets with at least the empty scales persistent. 



Spikelets with one perfect flower. 



Spikelets with 2 or 3 perfect flowers. 



29. Trisetum. 



30. AVENA. 



31. Arrhenatherum. 



32. Danthonia. 



33. Spartina. 



34. Atheropogon. 



35. Eleusine. 



Tribe IX. FESTUCEAE. 



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

 intermediate nerves. 

 Lateral nerves of the flowering scale pilose. 

 Lateral nerves of the flowering scale glabrous. 

 Second empty scale similar to the first. 

 Second empty scale very dissimilar to the first, broad 

 and rounded at the summit. 

 Flowering scales 5-many-nerved. 



Spikelets with two or more of the upper scales empty, 



broad and enfolding each other. 

 Spikelets with the upper scales flower-bearing, or smal- 

 ler and empty. 

 Empty basal scales 3-6. 

 Empty basal scales 2. 



Spikelets borne in fascicles which are arranged 



in a glomerate or interrupted panicle. 

 Spikelets borne in panicles or racemes but not 

 in fascicles. 

 Stigmas inserted at or near the apex of the 

 ovary : spikelets small. 

 Flowering scales with the nerves parallel. 

 Flowering scales with the lateral nerves 

 converging above toward the mid- 

 nerve. 

 Flowering scales strongly keeled on 

 the back, pubescent on some or all 

 of the nerves : hilum punctiform. 

 Flowering scales rounded on the back, 

 at least below : hilum linear. 

 Stigmas plainly inserted below the apex of 

 the ovary : spikelets large. 



3G. Tridens. 



37. Eragrostis. 



38. Sphenopholis. 



39. Melica. 



40. Uniola. 



41. Dactylis. 



43. Panicularia. 



42. POA. 



44. Festuca. 



45. Bromus. 



Tribe X. HORDEAE. 



Spikelets singly arranged at the rachis-nodes. 



Spikelets with the flowering scales with their backs 



to the rachis : empty scale 1. 

 Spikelets with the flowering scales with their sides to 

 the rachis : empty scales 2. 

 Spikelets 2-6 at each rachis-node. 



Empty scales usually as long as the flowering ones. 

 Empty scales wanting or minute. 



46. LoLiuM. 



47. Agroptron. 



48. Eltmus. 



49. Hystrix. 



1. TRIPSACTJM L. Tall perennial monoecious grasses, with stout root- 

 stocks, and spicate inflorescence. Spikes articulated, elongate. Staminate spike- 

 lets 2-flowered, in pairs at each joint of the upper portion of the axis, of 4 

 scales, the outer 2 empty, coriaceous and shining, the inner 2 thinner, each en- 

 closing a hyaline palet and a flower consisting of 3 stamens. Pistillate spike- 

 lets l-flowered, in excavations in the lower internodes of the rachis, the outer 

 scale very hard, thick and shining, concealing the more delicate remaining scales, 

 the fourth scale enclosing a flower with a slender style. Stigmas 2, exserted. 

 Grain enclosed in the appressed outer scale and the internode. 



