/•'/or a of the Palouse Region 19 



29. SPOROBOLUS. 



Inflorescence an open or contracted panicle: spikelets 1 -flowered, 

 occasionally 2-3-flowered. generally small: empty glumes mem- 

 branous, the first somewhat shorter: flowering glume membranous, 

 equalling or longer than the empty ones: grain free and often de- 

 ciduous. 



Panicle narrow, small: low, densely matted. S. depauperatis. 



Panicle open, large: tall. S. cryptaxdrus. 



S. depauperatus Scrib. Densely matted, 10-15 cm. high: culms strongly 

 decumbent at base: leaf blades 5-8 cm. long, narrow, involute, minutely 

 scabrous: culm leaves 4-5; ligules entire, acute: panicle very narrow, 2-5 cm. 

 long, erect, frequently with its base in the uppermost sheath: spikelets 2-2.5 

 mm. long: flowering glume acuminate, scabrous above. In low swales, 

 common. 



S. Cryptaildrus Gray. Culms .5-1 m. tall, erect, usually simple, smooth: 

 leaf blades flat, becoming involute, 10-15 CU1 - l° n g- 3~4 mm. wide; ligule 

 minute; sheaths long bearded at the throat: panicle erect, narrowly pyra- 

 midal, 10-20 cm. long, its base enclosed in the uppermost sheath; branches 

 mostly in pairs, ascending: spikelets crowded, leaden-colored, 1.5 mm. long. 

 Sandy bars of Snake River. 



30. POLYPOGOX. 



Inflorescence a spike-like panicle: spikelets 1 -flowered: empty 

 glumes each extended into an awn: flowering glume smaller, gen- 

 erally hyaline, short- awned from below the apex, with a palet 

 which is shorter than the flowering glume: grain free, enclosed in 

 the flowering glume and palet. 



P. monspeliensis Desf. Annual, with erect or ascending culms, 8-30 cm. 

 high: leaf blades flat, more or less scabrous; sheath loose, shorter than the 

 internodes: panicle densely flowered, oblong, rarely interrupted, 2-7 cm. 

 long: empty glumes elliptic, notched at the apex, about 2 mm. long, bearing 

 terminal awns 3 or 4 times as long: flowering glume truncate, 1 mm. long, 

 bearing a" terminal awn somewhat longer. Moist places near Snake River. 



31. AGROSTIS. 



Inflorescence a panicle: spikelets 1 -flowered: empty glumes 

 membranous, keeled, acute: flowering glume shorter, obtuse, hya- 

 line, sometimes bearing a dorsal awn; palet shorter than the flow- 

 ering glume, sometimes minute or wanting: grain free, enclosed 

 in the flowering glume. 



Palet present, one-third the length of the glume. A. ai.ba. 



Palet very minute or wanting. 



Branches of the dense narrow panicle spikelet-bearing to the base. 



A. EXARATA. 



Branches of the looser panicle, at least the lower ones, naked below. 

 Panicle narrow, the branches rather short: perennial. 



A. SCOULERI. 

 Panicle loose, the branches elongated: annual. A. SCABRA. 



