SYSTEMATIC BOTANY. 



2. Spikelets 2-flowered, the upper perfect, the lower staminate or neu- 



tral, and in the latter case usually reduced to a single palea. 



Spikelets single, with the terminal flower perfect, not surrounded by bristles, 

 arranged in racemes, panicles, or compound spikes. Panicum. 



Spikelets surrounded by several or many bristles, and arranged in a cylindrical 

 more or less compound spike. Setaria. 



Spikelets in pairs, one pedicellate and sterile ; the other with the terminal flower 

 perfect and awned, all arranged in spikes or racemes. A ndropogon. 



Spikelets in clusters of 2-3, i only with the terminal flower perfect and awned, 

 in panicles. Sorghum. 



Flowers monoecious ; barren flowers in terminal, numerous spikes ; fertile in soli- 

 tary, lateral spikes, inclosed in a leafy involucre of numerous bracts. Styles long and 

 slender. Zea. 



3. Spikelets 3-flowered, 2 of them imperfect or abortive, mostly reduced 



to single paleae. 



Spikelets in contracted panicles ; lower flower abortive or obsolete ; middle flower 

 perfect ; upper flower staminate. Holcus. 



Spikelets in nearly simple, cylindrical spikes ; the two lateral flowers neutral, re- 

 duced to awned paleae ; middle flower perfect, with awnless palea. A nthoxanthum. 



4. Spikelets more than 2 flowers, or if only 2 both are perfect. 



* SPIKELETS IN PANICLES OFTEN MUCH CONTRACTED AND SPIKE-LIKE. 

 t Lower palea with a conspicuous awn. 



Spikelets 3-6-flowered, in dense, i-sided clusters, forming a crowded panicle. 

 Glumes awned, somewhat rough and ciliate on the back, as also the lower palea. 

 Dactylis. 



Spikelets 3-10-6* owered, in open panicles, or contracted, spicate ones. Glumes 

 unequal. Paleae rounded on the back, awned at the apex. Festuca. 



Spikelets 5-1 2-flowered, in loose, at length drooping panicles. Glumes unequal. 

 Lower palea mostly 2-cleft, with a straight awn below the tip. Bromus. 



Spikelets 7-flowered, in a loose, racemose panicle. Lower palea 2-toothed at 

 apex, with an awn composed of the three twisted nerves rising from between the 

 teeth. Danthonia. 



Spikelets 3-6-flowered ; uppermost imperfect. Glumes unequal. Lower palea 

 rounded on the back, with a twisted awn, consisting only of the middle nerve, and 

 arising on the back below the 2-cleft tip. A vena. 



t + Lower paleee awnless. 



Spikelets compressed, 2-7-flowered, in open panicles, clothed with more or less of 

 a web-like down, but not bearded at base. Upper palea 2-toothed, deciduous, 

 together with the larger, s-nerved, lower palea. Poa. 



Spikelets 3-io-flowered ; flowers not webbed nor bearded at base. Paleae rounded 

 on the back ; upper one adhering to the inclosed grain, which is somewhat downy at 

 apex. Festuca. 



Spikelets 3-7-flowered ; flowers with a copious silky beard at base ; lower flower 

 with i stamen ; the others with 3 stamens. Glumes very unequal. Phragmites. 



* * SPIKF,LETS IN SIMPLE, TERMINAL SPIKES. 



Spikelets 3-io-flowered, attached singly tq the joints of the rachis, with the side 

 against it. Glumes 2, on opposite sides of the spikelet. Triticum. 



Spikelets solitary at each joint of the rachis, 2-3-flowercd. Glumes 2, opposite, 

 subulate, shorter than the flowers. Sccale. 



Spikelets 2-7-flowered, in clusters of 2-4 at each joint of the rachis. Glumes side 

 by side on the front of the spikelets, rarely none. Elymus. 



