230 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



Agropyron pauciflorum (A. tenerum) has been cultivated in the 

 Northwestern States on a commercial scale under the name slender 

 wheatgrass and the seed has been carried by seedsmen in that region. 

 A. smithii, bluestem, often called also western wheatgrass and some- 

 times Colorado bluestem, is a source of hay in alkaline meadows through 

 the Western States. A. spicatum, or bluebunch wheatgrass, and 

 A. dasystachyum are important range grasses in the Northwestern 

 States. A. pauciflorum and A. subsecundum (A. caninum, so-called) 

 because of their abundance in the mountain grazing regions are also 

 important. A. repens, quackgrass, is a good forage grass, but, because 

 of its creeping rhizomes, is a troublesome weed, especially in the 

 Eastern States where it is widely introduced. The species with strong 

 creeping rhizomes are valuable for holding embankments or for holding 

 sandy soils. 



The divisions of the species into those with rhizomes and those 

 without is convenient and usually definite when the entire base is 

 present but some species normally without rhizomes (as A. spicatum) 

 may rarely produce them and species in which rhizomes occur may not 

 show them in herbarium specimens. 



la. Plants with creeping rhizomes. 



Lemmas awned, the awn divergent at maturity. 



Lemmas pubescent 9. A. albicans. 



Lemmas glabrous 10. A. griffithsii. 



Lemmas awnless or with a short straight awn. 



Glumes rigid, gradually tapering into a short awn. 



Culms 10 to 20 cm tall, usually shorter than the leaves; sandy seacoast, 



California 4. A. arenicola. 



Culms 30 to 60 cm tall, exceeding the leaves; interior 5. A. smithii. 



Glumes not rigid, acute or abruptly awn-pointed. 



Lemmas glabrous (sometimes pubescent in A. riparium). 

 Blades lax, flat, usually sparsely pilose on the upper surface. 



2.. A. REPENS. 

 Blades firm, stiff, often involute, not pilose. 



Spikelets much compressed, closely imbricate, the spike dense. 



3. A. PUNGENS. 

 Spikelets not much compressed, somewhat distant, the spike slender. 



8. A. RIPARIUM. 



Lemmas pubescent. 



Spike 6 to 12 cm long; spikelets 1 to 1.5 cm long; glumes 6 to 9 mm long. 



6. A. DASYSTACHYUM. 



Spike longer, as much as 25 cm long; spikelets as much as 2.5 cm long; 



glumes as much as 13 mm long 7. A. elmeri. 



lb. Plants without creeping rhizomes. 



Spikelets much compressed, closely imbricate, divergent. 1. A. cristatum. 

 Spikelets not much compressed nor closely imbricate. 

 Spikelets awnless or awn-tipped only. 



Lemmas pubescent 14. A. latiglume. 



Lemmas glabrous. 



Internodes of rachilla scaberulous; glumes rather narrow, about half as 

 long as the spikelet. 



Blades involute (rarely flat) 19. A. inerme. 



Blades flat 21. A. parishii. 



Internodes of rachilla villous; glumes broad, nearly as long as the spike- 

 let 13. A. PAUCIFLORUM. 



Spikelets awned. 



Culms prostrate-spreading 17. A. scribneri. 



Culms erect (decumbent at base in A. pringlei). 

 Rachis finally disarticulating. 



Glumes narrow, 2-nerved; awns of lemma spreading, out-curved or 



recurved 22. A. saxicola. 



Glumes broader, with usually 3 to 5 distinct scabrous nerves; awn of 

 lemma straight, erect.. 1 23. A. saundersii. 



