Flora of the Palouse Region 1 7 



Tribk 6. HORDEAE. 



Spikelets solitary at the notches of the rachis: glumes usually acute or awned. 



50. AGROPYRON. 

 Spikelets 2-6 at each notch of the rachis: glumes mostly long-awned. 



Rachis readily breaking into joints. 



Spikelets 1 -flowered, 3 at each joint, only the central one perfect. 



51. HORDEl'M. 

 Spikelets 1-5-flowered, 2-4 at each joint, all perfect. 



52. SITANIOX. 

 Rachis not readily breaking into joints: spikelets T-7-flowered, 2-4 at 



each joint. 53. ELYMUS. 



24. PANICUM. 



Spikelets 1-2-flowered, when 2-flowered the lower one stami- 

 nate: empty glumes 2, membranous: flowering glumes 2, the lower 

 empty or with a staminate flower, the upper papery, shining, en- 

 closing a similar palet and with a perfect flower: awns none (in 

 ours): grain free, enclosed in the hardened flowering glume and 

 palet. 



Branches of the panicle spikelet-bearing to the base. P. crus-galu. 

 Branches of the panicle capillary, naked below, bearing but few scattered 

 spikelets. 



Spikelets acuminate. P. capielare. 



Spikelets obtuse. P. scribneriaxcm. 



P. crus-galli L. Annual, erect, .6-1.5 m. tall: leaf blades 15-60 cm. long, 

 6-25 mm. wide, glabrous or nearly so: panicle dense, the branches spike- 

 like, bearing spikelets to the base; spikelets crowded on the lower side of 

 the branches: empty glumes ovate, pointed: flowering glume of the neutral 

 flower bearing an awn 4-30 mm. long. Introduced and becoming abundant. 



P. capillare L. Annual, culms erect or decumbent at base, 15-30 cm. tall, 

 mostly simple: leaf blades 15-30 cm. long, pubescent: sheaths villous: panicle 

 10-15 cm - l° n g- the capillary branches solitary or in twos, ascending, 

 branched and spikelet-bearing above the middle: spikelets 3 mm. long, ovoid, 

 usually on peduncles as long or longer. In sandy soil, common. 



P. SCribnerianum Nash. Annual, the culms 20-50 cm. tall, erect or as- 

 cending, simple or branched above: culm leaves about 6, the blades lanceo- 

 late, 4-8 cm. long, 6-10 mm. wide, stiff, ascending, glabrous; sheaths pilose, 

 loose: panicles oblong or pyramidal, 3-8 cm. long, loose, exserted or the 

 smaller one included: spikelets turgid, ovoid, 3 mm. long. Sandy banks of 

 Snake River. 



25. ARISTIDA. 



Spikelets narrow, 1 -flowered: empty glumes 2, narrow, often 

 carinate: flowering glume 1, ridged and convolute, bearing 3 awns 

 which are occasionally united at the base; palet 2-nerved: grain 

 free, tightly enclosed in the scale. 



