GRAMINE^E. (GRASS FAMILY.) 625 



H- 4+ Rhachis bearing a rudimentary second flower or short bristle (except in species of 



n. 33). 



32. Apera. Flowering glume bifid, awiied. Panicle very loose and delicate. 



33. Calamagrostis. Flowers hairy-tufted at base. Glumes membranaceous. Palet thin. 

 '34. Ammophila. Spikelets large. Flowers hairy-tufted at base. Glumes and palet 



chartaceous. 



Tribe VII. AVENE^E. Spikelets 2 -several -flowered, panicled, the rhachis or base 

 of the flowers often bearded ; upper flower imperfect or rudimentary (except in n. 37). 

 Flowering glume bearing a twisted, bent or straight awn on its back or below the apex. 



* One of the flowers staminate only. 



35. Arrhenatherum. Lower flower starniuate, long-awned ; middle flower perfect, nearly 



awnless ; the upper rudimentary. 



86. Holcus. Flowers 2, the lower perfect, awnless, the upper staminate, awned. 

 * * Flowers all perfect or the uppermost usually rudimentary. 



37. Aira. Spikelets very small, in a diffuse panicle. Flowers 2, perfect, awned toward 



the base. 



38. Deschampsia* Spikelets 2-flowered, with a hairy rudiment. Glumes thin-scarious, 



the flowering one erose-truncate, awned near the middle. 



39. Trisetum. Spikelets 2 - several-flowered. Flowering glume thin, compressed, cari- 



nate, 2-toothed, awned above by the excurrent mid-nerve. 



40. A vena. Spikelets 2 -several-flowered. Flowering glume hard and firm, rounded on 



the back, 5-9-nerved, the mid-nerve long-excurrent at or below the 2-toothed apex. 



41. Danthonia. As Avena, hut the 3 middle nerves of the flowering glume running into 



a flattish twisted awn from between the teeth. 



Tribe VIII. CHLORIDES. Spikelets 2 - several-flowered with one or more of the 

 upper flowers imperfect (flower 1 and perfect in n. 45), arranged in 2 rows upon the 

 rhachis of a 1-sided spike. 



* Spikelets with one perfect flower. 



42. Cynodon. Spikes 3-5, slender, digitate. Flower and the rudiment awnless. 



43. Ctenium. Spike solitary, terminal. Flowers 4-6, the middle one perfect. 



44. Gymnopogon. Spikes filiform, racemose. Spikelets remote, of a perfect flower and 



an awned rudiment. 



45. Schedonnardus. Spikes 3 - 9, slender, scattered, distant. Spikelets small, 1-flow- 



ered, awnless. 



46. Bouteloua. Spikes scattered (rarely 1 and terminal), dense. Glume of perfect flower 



3-toothed. Rudimentary flowers 1 - 3-awned. 



* * Spikelets with two or more perfect flowers ; awns none. 



47. Eleusine. Spikes digitate, dense. 



48. Lieptochloa. Spikes racemose, slender. Spikelets small, alternate. 



* * * Spikelets dioecious; spikes small, very dissimilar. 

 40, Buchloe. Pistillate spikes capitate, sessile, the spikelets 1-flowered ; staminate spikes 



(2 or 3) on a peduncle, the spikelets 2 - 3-flowered. 



Tribe IX. FESTUCE^E. Spikelets few -many, flowered, panicled, the uppermost 

 flowers often imperfect or abortive. Glumes pointless or the flowering ones tipped with 

 a straight awn or bristle. 

 * Flowering glume 1 -3-nerved, 2- 3-toothed. Rhachis short-bearded or glabrous. 



50. Triodia. Rhachis of the spikelet bearded. Nerves of the flowering glume 3, villous, 



at least the middle one more or less excurrent. 



51. Diplachne. Rhachis glabrous. Glume 1- 3-nerved, with 2 small teeth, and a short 



awn in the cleft. 



* * Glume 3-nerved, entire or 2-toothed and mucronate between the teeth. Rhachis and 

 flowers long- villous. Tall reeds with ample panicles. 



52. Phragmites. Spikelets 3-7-flowered lowest flower naked, staminate or neutnfl 



Glume entire. 



53. Arundo. As n. 52, but flowers all perfect. Glume bifid. 



