Infrequent in open forests on sandy soil, in mud at edge of ponds and lakes, 

 along streams and low wet ground, in Okla. (Mayes Co.) and e., s.e. and n.-cen. 

 Tex., summer-fall; s.e. U.S. n. to N.C., Tenn., 111. and Mo., w. to Kan., Okla. 

 and Tex. 



2. Tridens albescens (Vasey) Woot. & Standi. White tridens. 



Tufts robust; culms 3-10 dm. long, erect; basal sheaths not or obscurely 

 keeled; panicles spikelike, 8-25 cm. long, 5-13 mm. broad, very pale in color; 

 lemmas about 3 mm. long, 3-nerved, the nerves ending well within the distal 

 margin and glabrous (hair, if present, confined to the basal callus of the lemma. 



Abundant in roadside ditches, streamsides, overflows, in playa lakes, draws 

 and low-lying prairies throughout Okla and Tex. to N.M. (Lea Co.), summer- 

 fall; Okla. and Colo., s. to Tarn., N.L. and Coah. 



3. Tridens ambiguus (Ell.) Schult. 



Tufted; culms 6-10 dm. long, erect; basal sheaths keeled; panicle broadly to 

 narrowly obovoid, 8-15 cm. long, the branches stifily ascending; most pedicels 

 (of lateral spikelets) about 1 mm. long; spikelets erect, appressed to the branches; 

 lemmas 3-4 mm. long, the 3 nerves usually minutely excurrent and pubescent in 

 the lower two-thirds the length, or the lateral nerves scarcely excurrent in many 

 specimens. 



Infrequent to rare, wet pinelands, boggy areas and wet savannahs, extreme 

 e. Tex., late summer-fall; Coastal States, S.C. to Tex. 



16. Agropyron Gaertn. Wheatgrass 



Perennials; corners of base of blades discolored and minutely auriculate or 

 pointed; inflorescences spikelike, the axis usually slightly zigzag, unbranched, re- 

 maining intact; spikelets several-flowered, solitary (rarely in pairs) at each node, 

 sessile, laterally compressed, turned with one side appressed to the rachis (or 

 to the next spikelet above when crowded); all florets perfect or usually the 

 terminal 1 or 2 reduced; rachilla abscising above the glume and at the lower 

 part of each node; glumes lanceolate, acute, persistent, roundly keeled, equal, 

 firm, several-nerved (the nerves obscure in some species); lemmas roundly keeled, 

 5- to 7-nerved (nerves obscure in some species at some stages of maturity), firm 

 to subindurate, lanceolae, acute or in some species awned, eventually the lateral 

 margins revolute. 



A genus of about 100 or more species in temperate regions. 



1. Plants normally cespitose, non-rhizomatous 1. A. suhsecundum. 



1. Plants with creeping rhizomes; blades firm and strongly nerved (2) 



2(1). Glumes rigid, gradually tapering into a short awn, more or less asymme- 

 tric, the lateral nerves usually obscure 2. A. Smithii. 



2. Glumes not rigid, acute or abruptly awn-pointed, symmetric, the lateral nerves 



evident 3. A. repens. 



1. Agropyron suhsecundum (Link) Hitchc. Bearded wheatgrass. 



Green or glaucous, without creeping rhizomes; culms erect, tufted, 5-10 dm. 

 tall; sheaths glabrous or rarely pubescent; blades flat, 3-8 mm. wide; spike erect 

 or slightly nodding, 6-15 cm. long, sometimes unilateral from twisting of the 

 spikelets to one side, the rachis scabrous to scabrous-ciliate on the angles, 

 sometimes disarticulating; spikelets rather closely imbricate, few-flowered, the 

 rachilla villous, the callus of the florets short-pilose; glumes broad, rather 

 prominently 4- to 7-nerved, nearly as long as the spikelet, tapering into an awn; 

 lemmas obscurely 5-nerved, the nerves becoming prominent toward the tip, the 

 awn straight or nearly so, usually 1-3 cm. long. 



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