264 OHIO BIOLOGICAL SURVEY 



Hordeae. 



I. Spikelets solitary at each joint of the rachis. 



1. Spikelets with their backs or edges to the rachis. Lolium. (22) 



2. Spikelets with their sides to the rachis. 



a. Empty glumes 3-many-nerved. 



(a). Empty glumes lanceolate or linear; spikelets 3-many-flowered. 



Agropyron. (23) 

 (b). Empty glumes ovate; spikelets 2-6-flowered. Triticum. (24) 



b. Empty glumes 1-nerved, subulate ; spikelets with 2 perfect flowers. 



Secale. (25) 



II. Spikelets 2-6 at each joint of the rachis, some of them may be reduced. 



1. Spikelets 2-many-flowered. 



a. Empty glumes but little smaller than the flowering glumes. 



Elymus. (26) 



b. Empty glumes very small or none; spikelets in pairs. Hystrix. (27) 



2. Spikelets 1-flowered or with a vestigial second flower; in threes at each joint 



of the rachis. Hordcum. (28) 



Chlorideae. 



I. Spikelets 1-flowered, with no vestigial lemma. 



1. Spikelets articulated below the empty glumes. 



a. Rachis extending beyond the upper spikelet ; spikelets lanceolate. 



Spartina. (29) 



b. Rachis of the spikes not produced ; spikelets orbicular 



Bcckmannia. (30) 



2. Sprkelets articulated above the empty glumes ; spikes digitate. 



Capriola. (31) 



II. Spikelets with two or more flowers. 



1. With 2-several perfect flowers in each spikelet ; spikes usually digitate. 



Elcusine. (32) 



2. With 1 perfect flower in each spikelet ; spikes solitary or racemose. 



a. Spikes numerous, each with 12 or less spikelets. Atheropogon. (33) 



1). Spikes 4 or less, each with 25 or more spikelets. Bouteloua. (34) 



Agrostideae. 



I. Flowering glumes membranous, not firmer than the empty glumes. 



A. Lemma awnless or with a dorsal awn ; flowering glumes loosely enclosing 

 the grain. 



I. Empty glumes not conspicuously compressed; spikelets usually in open 

 or narrow panicles. 



(1). Lemma 1-nerved, awnless. Sporobolus. (35) 



(2). Lemma 3-5-nerved. 



