62 POACEAE. 



the usually continuous rachis, the side of the spikelet, that is the 

 edge of the glumes, toward the rachis; lemmas rigid, rounded on 

 the back, 5-7-nerved, usually acute or awned at the apex; palea 

 often with hairy keels; grain pubescent at the apex. 



Plants tufted, without rootstocks; spikelets subcylindric. A. tenerum. 



Plants with creeping rootstocks. 



Spikelets compressed, spreading; leaves pale, rough on the 



back. A. occidentale. 



Spikelets subcylindric, erect; leaves green, smooth on the 



back. A. repens. 



Agropyron tenerum Vasey. Slender Wheat-grass. Perennial, tufted; 

 stems erect, 30-100 cm. high, rather slender, glabrous; stem leaves 3 or 4, the 

 blades becoming involute, scabrous on both sides, the sheaths glabrous and 

 shorter than the internodes; spike 10-20 cm. long, narrow, the spikelets densely 

 crowded; lemmas linear-oblong, 5-nerved, scabrous, acuminate or short-awned. 



Rare west of the Cascade Mountains; common in the interior. 



Agropyron occidentale Scribn. (A. smithii Rydb.) Bluestem. Whole plant 

 pale or glaucous; stems erect, 30-100 cm. high; leaves firm, the nerves thick 

 and prominent; spike 8-15 cm. long, compact; spikelets 7-13-flowered, 12-20 

 mm. long, glabrous; lemma firm, awn-pointed, the nerves faint. 



High sea-beaches, rare; common in the interior. 



Agropyron repens L. Couch or Quack-grass. Stems erect, 100-150 cm. 

 high; leaf blades green, pilose above, the nerves not prominent; spike 5-15 cm. 

 long; spikelets 5-flowered; lemma glabrous or nearly so, strongly nerved, 

 usually awn-pointed. 



Sparingly introduced; a very pernicious weed. 



91. ELYMUS. RYE-GRASS. 



Perennial or annual grasses with spike-like inflorescences which 

 do not readily break up into segments; spikelets 1 7-flowered, 

 2-4 at each joint of the rachis or rarely solitary; glumes entire, 

 equal, rigid, narrow; lemmas acute, acuminate or awned, entire. 



Glumes subulate, obscurely nerved. 



Annual; glumes awned. E. caput-medusae. 



Perennial plants with creeping rootstocks; glumes not 



awned. 

 Lemma glabrous, often glaucous; glumes not 



hirsute. E. triticoides. 



Lemma scabrous-puberulent; glumes sparsely 



hirsute. E. Vancouver ensis. 



Glumes lanceolate, distinctly nerved. 



Culms very stout, 1-2 m. tall; plants with rootstocks. E. arenarius. 

 Culms slender, seldom 1 m. tall; plants without root- 

 stocks. 



Lemma not ciliate. E. glaucus. 



Lemma ciliate. 



Awns long. E. hirsutus. 



Awns short. E. virescens. 



Elymus caput-medusae L. Glabrous annual; stems 20-^50 cm. high, 

 erect or geniculate at base; leaves 1-2 mm. broad, becoming involute; spike 

 stout, erect, green or becoming purplish, 1-4 cm. long without the awns; 



