400 GRAMINE^E. (GRASS FAMILY.) 



with dorsal awn : palet shorter than flowering glume, often reduced to a small scale 

 or wanting. Stamens 3. 



20. Ciima. Spikelets much flattened, in an open spreading panicle. Outer glumes 



strongly keeled, hispid on the keel, the upper somewhat longer : flowering glume 

 stalked above the outer glumes and about the same length, 3-nerved, short-awned on 

 the back Dear the apex : palet nearly as long as its glume, one-nerved. Stamen one. 



21. A in iikophih*. Outer glumes large- nearly equal, rigid, thick, keeled, 5-nerved : 



flowering glume similar in texture, about equal iu length, sometimes mucronate: 

 palet as long as its glume, of similar texture, 2-keeled and sulcate between the keels. 

 Hairs at the base of the flower usually scanty and short. 



•*-■•- A glabrous or hairy bristle standing opposite the palet. 

 •22. Deyeuxia. Outer glumes about equal, keeled, awnless : flowering glume usually 

 with a ring of hairs surrounding its base, entire or 2 to 4-toothed, usually with a 

 dorsal awn : palet narrow, 2-nerved and 2-keeled. 



Tribe VI. Spikelets 2 to many-flowered, often paniculate : flowering glumes commonly 

 with a dorsal or terminal geniculate awn : rhachis more or less produced beyond the 

 flowers. — AvENEiE. 



23. Deschampsia. Spikelets 2-flowered, mostly in a loose panicle with slender branches. 



Rhachis hairy and produced into a hairy bristle, which rarely bears an empty glume. 

 Outer glumes acute, keeled, with scarious margins: flowering glumes obtuse or 

 toothed, with a fine dorsal awn below the middle : palet prominently 2-nerved s often 

 2-toothed. 



24. Trisetum. Spikelets 2 to 5-flowerei, in a dense or open panicle. Rhachis usually 



hairy and produced into a bristle at the base of the upper flower. Outer glumes 

 unequal, keeled, with scarious margins : flowering glumes of similar texture, keeled, 

 2-toothed at apex, the teeth sometimes prolonged into bristle-like points, the middle 

 nerve furnished with an awn attached above the middle, which is usually twisted at 

 the base and bent in the middle : palet hyaline, narrow, 2-nerved, 2-toothed. 



25. Avena. Spikelets unusually large, 2 to 5-flowered, the uppermost generally imperfect, 



in a loose panicle. Rhachis hairy below the flowers. Outer glumes nearly equal, 

 lanceolate, scarious : flowering glumes firmer, shortly bifid, with a long dorsal twisted 

 awn below the apex : palet as in last. 



26. Daiithonia. Spikelets 3 to many-flowered, in a panicle or simple raceme. Rhachis 



hairy and produced beyond the flowers in a stipe or imperfect flower. Outer glumes 

 narrow, keeled, usually as long as the spikelet : flowering glumes convex on the back, 

 7 to 9-nerved, with two terminal teeth or lobes, and with a flattish twisted and bent 

 awn between the teeth : palet broad, 2-keeled, obtuse or 2-pointed. 



Tribe VTL Spikelets one to many-flowered, sessile and secund in two rows along the 



rhachis of one-sided spikes. — Chlorides 



* One fertile flower in each spikelet. 



27. Schedonnardus. Spikelets one-flowered, solitary at each joint of the slender tri- 



angular rhachis of the paniculate spikes, and partly immersed in an excavation ; the 

 spikes alternate and distant. Outer glumes acuminate, unequal, the longer equalling 

 the flowering glume, which is linear-acuminate and thickish at the keeL 



28. Bouteloua. Spikes numerous in a racemose panicle ; spikelets densely crowded, each 



consisting of one perfect flower, and a stalked pedicel bearing empty glumes and 1 to 

 3 stiff awns. Outer glumes unequal, acute, keeled : flowering glume broader, usually 

 thicker, with 3 to 5 lobes, teeth, or awns. 



* * Two to many fertile flowers in each spikelet 



29. Buchloe. Spikelets dioecious, or rarely monoecious, heteromorphous. — Male plant. 



Spikelets 2 to 3-flowered in 2 or 3 short spikes at the summit of the culm, 5 or 6 

 closely approximated in each spike. Outer glumes unequal, 1-nerved, the lower one 

 half as Ion- as the flower above it, the upper shorter : flowering glumes and palets of 

 equal length, membranaceous, the former 3-nerved, the latter 2-nerved. —Female 

 plant. Spikelets closely approximated in short capitate spikes, which are mostly 



