POACEAE. 39 



scabrous, the loose sheaths exceeding the internodes; panicle narrow, 10-30 

 cm. long, the densely-flowered branches mostly solitary and erect; spikelets 

 nearly orbicular, flattened, 2 mm. long. In shallow water or very moist 

 places. 



61. AGROPYRON. Wheatgrass. 



Perennials with simple stems and terminal spikes; spikelets 

 3-many-flowered, sessile, single and alternate at each notch of 

 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 densely tufted, seldom producing stolons. 



Spikelets subterete, the florets close; lemma short-awned. A. tenerum. 

 Spikelets flattened, the florets loose; lemma usually awned. 



Glumes awnless. A. spicatum. 



Glumes awned. A. flexuosum. 



Plants producing abundant stolons. 



Lemma puberulent. A. lanceolatum 



Lemma glabrous. 



Leaves pale, scabrous above; nerves prominent. A. occidentale. 



Leaves green, pubescent above; nerves rather obscure. A. repens. 



Agropyron tenerum Vasey. Perennial, tufted; stems erect, 30-100 cm. 

 high, rather slender, glabrous; stem leaves 3 or 4, the blades becoming in- 

 volute, 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. 

 Common in low ground. 



Agropyron spicatum (Pursh) Scribn. & Smith. Wheat Bunch-grass. Stems 

 50-100 cm. tall, densely tufted, glabrous and glacuous; stem leaves 3, the 

 blades becoming strongly involute, minutely pubescent above, scabrous 

 beneath, the sheaths smooth or pubescent; spikes erect, 5-15 cm. long; 

 spikelets regularly scattered, lanceolate-oblong, 10-20 mm. long, without 

 the awns; lemma tipped with a stout divergent awn, 1-2 cm. long. Very 

 abundant on dry hills and exposed edges. Under some conditions, the plants 

 produce long stolons. 



Agropyron spicatum inerme (Scribn. & Smith) Heller. Stems usually 

 more slender; spikelets smaller; awns wanting. Very abundant on dry hills 

 and exposed ledges. The species and the subspecies are frequently found 

 growing together. 



Agropyron flexuosum Piper. {Sitanion flexuosum Piper.) Very similar 

 in appearance to A. spicatum. Spikelets looser, flexuous; spikelets often two 

 at a node; glumes awned, often trifid; lemma usually bifid, its awn 3.5-4 cm. 

 long. Banks of Snake River at Wawawai. 



Agropyron lanceolatum Scribn. & Smith. Stems erect, 60-120 cm. tall, 

 smooth, from elongated creeping rootstocks; stem leaves 4, the blades becoming 

 involute, rather narrow, ascending, strigose above, smooth beneath, the sheath 

 loose, exceeding the internodes; spikes erect, 15-25 cm. long; spikelets not 

 crowded, 2-2.5 cm. long, 6-10-flowered; lemmas sparsely pubescent, tipped 

 with a very short awn. Common on the dry sandy bars of Snake River. 



Agropyron occidentale Scribn. Bluestem. Whole plant pale or glaucous; 

 stems erect, 30-100 cm. high; leaves firm, the nerves thick and prominent; 



