GRASSES OF OHIO 263 



((1)). Lemma not coriaceous in fruit; grain beaklcss, not ex- 

 serted. 



a. Rachilla not prolonged behind the palet of the uppermost 



sterile flower ; spikelets in an open panicle. 



Eragrostis. (7) 



b. Rachilla prolonged behind the palet of the uppermost 



flower; spikelets 2-5-flowered, usually in a more or less 

 contracted panicle. 



(a). Inner empty glume broad and rounded at the tip; 

 very dissimilar from the outer glume. 



Sphenopholis. (8) 



(b). Inner empty glume similar to the outer. 



Koeleria. (9) 



((2)). Lemma coriaceous in fruit, grain beaked and exserted. 



Korycarpus. (10) 



(2). Callus and nerves of the lemma densely bearded, not cobwebby. 

 ((1)). Palet not ciliate-f ringed ; internodes of the rachilla short. 



T rid ens. (11) 



((2)). Palet conspicuously ciliate-fringed; internodes of the 



rachilla long. Triplasis. (12) 



B. Spikelets of 2 kinds, in small clusters, the upper perfect ones surrounded 

 by sterile spikelets below. Cynosarus. (13) 



II. Rachilla with hairs longer than the flowering glumes. Phragmites. (14) 



Aveneae. 



I. Spikelets not deciduous, the empty glumes persistent. 



A. Spikelets 2-many-flowered; rachilla prolonged beyond the upper glume. 



1. Awn projecting from between the lobes of the lemma, flattened and 



twisted. Danthonia. (15) 



2. Awn of the lemma dorsal, not flattened. 



(1). Spikelets 2-flowered, the upper bisporangiate, the lower staminate 

 and its glumes strongly awned. Arrhenathenim. (16) 



(2). Spikelets 2-several-flowered; flowers all bisporangiate or the 

 uppermost imperfect. 



a. Lemma keeled ; awn rising from above the middle ; spikelets 



less than y 2 inch long. Trisetum, (17) 



b. Lemma rounded on the back. 



(a). Spikelets over l / 2 in. long; grain furrowed, usually ad- 

 herent to the flowering glumes. Arena. (18) 



(b). Spikelets less than l / 2 in. long; grain not furrowed, free. 



Deschampsia. (19) 



B. Spikelets with 2 bisporangiate flowers; rachilla not prolonged beyond the 



upper flower. Aspris. (20) 



II. Spikelets deciduous ; lower flower bisporangiate, upper staminate with a hook- 



like awn; plant velvety. Nothoholcus. (21) 



