GENEKA OF GRASSES OF THE UNITED STATES. 11 



Key to the genera of Festuceae Continued. 



2Ga. Callus of florets bearded ; lemmas erose at the summit 7. FLUMINEA. 



26b. Callus not bearded (lemmas cobwebby at base in Poa) ; lemmas not 



erose (slightly in Puccinellia) 27 



27a. Lemmas keeled on the back (somewhat rounded in Poa scabrella 



and its allies) 28 



28a. Spikelets strongly compressed, crowded in one-sided clusters 



at the ends of the stiff, naked panicle branches 21. DACTYLIS. 



28b. Spikelets not strongly compressed, not crowded in one-sided 



clusters 29 



29a. Lemmas awned from a minutely bifid apex (awnless or 

 nearly so in Bromus unioloides and B. brizaeformis) ; 



spikelets large 2. BROMUS. 



20b. Lemmas awnless ; spikelets small 8. POA. ' 



27b. Lemmas rounded on the back (slightly keeled toward the summit 



in Festuca and Bromus) 30 



30a. Glumes papery ; lemmas firm, strongly nerved, scarious-mar- 

 gined ; upper florets sterile, often reduced to a club-shaped 

 rudiment infolded by the broad upper lemmas; spikelets 



tawny or purplish, usually not green 24. MELICA. 



30b. Glumes not papery ; upper florets not unlike the others 31 



31a. Nerves of the lemma parallel, not converging at the sum- 

 mit or but slightly so ; lemmas awnless mostly obtuse. 32 

 32a. Nerves prominent ; plants usually rather tall, grow- 

 ing in woods or fresh-water marshes 4. PANICULARIA. 



32b. Nerves faint ; plants low, growing in saline soil. 



6. PUCCINELLIA. 



31b. Nerves of the lemma converging at the smmmit ; lemmas 

 awned or pointed (upper florets only minutely awn- 

 tipped in Bromus brizaeformis) 33 



33a. Lemmas entire, awned from the tip or pointed 

 (minutely toothed in Festuca elmeri and F. 



gigantea} 3. FESTUCA. 



33b. Lemmas awned or awn-tipped from a minutely bifid 



apex 2. BROMTJS. 



TRIBE 3, HORDEAE. 



Spikelets 1 to several flowered, sessile on opposite sides of a jointed 

 or continuous axis forming symmetrical (not one-sided) spikes. 



This small but important tribe, found in the temperate regions of 

 both hemispheres, includes our most important cereals, wheat, barley, 

 and rye. The rachis is flattened or concave next to the spikelets, or 

 in some genera is thickened and hollowed out, the spikelets being 

 more or less inclosed in the hollows. In Triticum and its allies there 

 is one spikelet at each node of the rachis; in Hordeum and its allies 

 there are two or three at each node. In Lolium and its allies the 

 spikelets are placed edgewise to the rachis, and the first or inner 

 glume is suppressed except in the terminal spikelet. The rachilla of 

 the spikelet disarticulates at maturity in several genera. In some 

 species of Elymus and especially in Sitanion the glumes are very 



