2G POACEAE 



Lemma long-hairy towards the apex. 

 Lemma about 5 mm. long. 



Glumes green, rarely slightly tinged with purple; lemma nearly glab- 

 rous below. 8. S. Leltermanii. 

 Glumes purpUsh with paler margins; lemma pubescent throughout, 

 though more densely so above. 9. S. pineinnun. 

 Lemma about 8 mm. long. 10. S. Scribneri. 

 Lemma equally hairy throughout. 

 Sheaths glabrous. 



Empty glumes scarious or hyaline; their nerves hence prominent. 



Lemma 4-6 mm. long, spindle-shaped when mature; callus short. 

 Stem-leaves broader than the basal leaves, often flat; sheaths 



with a ring of hairs at the throat. 11. S. viriduli. 



Stem-leaves as well as the basal leaves very narrow, involute; 

 sheaths glabrous. 

 Plant green; s heat lis close; inflorescence distinctly e.xserted. 



12. S. Columbiana. 

 Plant pale and glaucous; sheaths loose; inflorescence included 

 or barely exserted; awn glabrous. 13. S. arida. 



Lemma 6-7 mm. long, almost cylindric; callus long and pointed. 



14. S. Nelsonii. 

 Empty glumes firm, thickisli, herbaceous; the nerves not prominent. 



Lemma about 5 mm. long; leaf-blades narrow and involute. 



15. 5. minor. 

 Lemma 8-10 mm. long; leaf-blades broad. 



Panicle slender; stem low and slender. 9. S. Scribneri. 



Panicle stout and dense; stem tall and stout. 16. S. Vaseui. 

 Sheaths and lower leaf-blade pubescent. 17. S. Williajnsii. 



Awns plumose or subplumose at least below. 



Hairs of the awns less than 1 mm. long; empty glumes 10-12 mm. long. 

 Ligules 1 mm. long or less. 



Sheaths, at least the lower ones, hairy. IS. S. Elmeri. 



Sheaths glabrous. 19. S. oregonensis. 



Ligules 2-4 mm. long. 20. S. Thurberiana. 



Hairs of the awns 3-6 mm. long; empty glumes 15-18 mm. long. 



21. S. speciosa. 



19. ORYZOPSIS Michx. Mountain Rice. 



Lemma glabrous, or pubescent with short appressed hairs. 



Spikelets, exclusive of the awn, 2.5-5 mm. long; leaves slender and involute. 



Awn less than 2 mm. long, much shorter than the glume; outer glumes 3-4 mm. 



long. 1. O. pungens. 



Awn 4—8 mm. long, much longer than the glume. 



Inflorescence very narrow, with short erect branches ; outer glumes 3-5 mm. 



long. 2. O. exigua. 



Inflorescence at length open, with long spreading or reflexed branches ; outer 

 glume about 2.5 mm. long. 3. O. micrantha. 



Spikelets, exclusive of the awn, 6-8 mm. long; leaves broad and usually flat. 



4. O. asperifolia. 

 Lemma with long loose hairs. 



Inflorescence open; plant 3-6 dm. high. 5. O. Bloomeri. 



Inflorescence narrow and spike-like; plant 1-3 dm. high. 6. O. Webberi. 



20. ERIOCOMA Nutt. Indian Millet, Wild Rice. i. E. hymenoidrs. 



21. MUHLENBERGIA Schreb. 



Panicle contracted, narrow, spike-like, the short branches rarely spreading. 



Empty glumes awl-shaped; leafy and branched plants, with long rootstocks covered 

 by imbricated scales. 

 Lemma not awned; basal hairs not equalling the lemma. 



Empty glumes about equalling the lemma in length, sharp-pointed, aboiit 3 



mm. long. 1. M. meiicana. 



Empty glumes exceeding the lemma, generally twice as long, awned, about 

 5 mm. long. 2. A/, racemosa. 



Lemma distinctly awned; basal hairs equalling the lemma. 3. M. comata. 

 Empty glumes lanceolate to ovate. 



Second glume not toothed or slightly so. 



Lemma awnless oi rarely very short-awned. 



Empty glumes more than half as long as the lemma. 



Plant 1.5-7 dm. high; sheaths close; empty glumes acuminate, lanceolate. 

 Lemma scabrous, green or dark. • 



Panicle dense, obtuse, 5-10 mm. wide. 4. At. Wrightii. . 



Panicle slender and lax, attenuate at the apex, less than 5 mm. 

 wide. 5. M. cuspidata. 



Lemma more or less purplish, sparingly long-hairy. 



6. A/. Thurberi. 

 Plant less than 1.2 dm. high; sheaths loose; lower leaves lanceolate, 

 short, squarrose; empty glumes ovate, acute. 7. A/, squarrosa. 

 Empty glumes less than half as long as the lemma, obtuse or abruptly 

 acute. 

 Spikelets (excluding the awn if present) 1.5 mm. or more long. 

 Plant with a strong perennial, scaly rootstock. 



