202 



NORTH AMERICAN FLORA 



[Volume 17 



Leaf -blades ob- 

 long-lanceolate, 

 2-6 mm. wide. 

 Leaf-blades elon- 

 gate, more 

 than 6 mm. 

 wide. 

 Spikelets hispid 

 along the 

 margin of the 

 glumes. 

 Spikelets gla- 

 brous or pu- 

 bescent but 

 not hispid on 

 the margins 

 of the glumes. 



I. DlSTANTIFl,ORA. 



I^eaf -blades elongate, usually more than 15 cm. long, narrowed toward 

 the base. 

 Spikelets about 2 mm. long or less. 



First glume acute; second glume about two thirds as long as the 

 fruit. 

 Spikelets 1.5 mm. long; leaf -blades involute. 

 Spikelets 2 mm. long; leaf -blades scarcely involute. 

 First glume rounded or truncate; second glume about as long as 

 the fruit. 

 Spikelets about 3.5 mm. long. 

 Leaf -blades usually less than 10 cm. long, not narrowed toward the base; 

 spikelets 2.5-3 mm. long. 

 Blades of mid-culm long-acuminate, usually 2-3 mm. wide. 

 Blades of mid-culm abruptly acute, usually 4—6 mm. wide. 



II. Geminata. 

 Nodes glabrous. 



Spikelets not more than 2.4 mm. long; glumes and sterile lemma not 



papery. 

 Spikelets 3 mm. long; glumes and sterile lemma papery. 

 Nodes bearded. 



XVII. PARVEPOUA. 



XVIII. Haenksana. 



III. Fasciculata. 



Spikelets 2—4 mm. long. 



Spikelets strongly reticulate- veined, 2—3 mm. long, glabrous. 

 Spikelets scarcely reticulate- veined, or so only near the apex. 

 Spikelets not more than 2 mm. long, glabrous. 

 Spikelets more than 3 mm. long, pubescent. 

 Rachis scabrous but not bristly. 

 Rachis pilose with bristly hairs. 



Plant more or less velvety; leaf -sheaths not papillose. 

 Plant not velvety; leaf -sheaths papillose. 

 Spikelets 5-6 mm. long. 



IV. DlCHOTOMIFLORA. 



Plants annual. 



Panicle narrow, less than 1 cm. wide. 

 Panicle open, the branches ascending or spreading. 

 Leaf -sheaths glabrous. 

 Leaf -sheaths papillose-hispid. 

 Plants perennial, the base decumbent and rooting. 



Spikelets acute ; fruit not acuminate ; culms usually less than 1 meter 



tall. 

 Spikelets and fruit acuminate; culms usually more than 1 meter tall. 

 Ligule 1 mm. long; nodes green; spikelets 3.3-3.7 mm. long. 

 Ligule 3 mm. long; nodes black in drying; spikelets 4—5 mm. long. 



XIX. MlIyLEGRANA. 



LP. distantiflorum, 



2. P. utowanaeum. 



3. P. Ckapmani. 

 5. P. Revcrchoni. 



4. P. ramisetum. 

 6. P. firmulum. 



7. P. geminatum. 



8. P. paludivagum. 



9. P. barbinode. 



11. P.fasciculatum, 

 10. P. reptans. 

 13. P. adspersum. 



12. P. 



14. P. 



15. P. 



molle, 



arizonicum 

 texanum. 



16. P. Vaseyanum. 



17. P. dichotomifiorum, 



18. P. bartowense. 



19. P. aquaticum. 



20. P. sucosum. 



21. P. elephantipes, 



V. Capiixaria. 

 Panicles erect. 



Inflorescence not composed of approximate nor implicate panicles. 

 Panicles more than half the length of the entire plant. 



Panicles narrow, usually less than half as broad as long. 

 Panicles as broad as long. 



Panicles not more than one-third the entire height of the plant. 

 Spikelets not more than 2 mm. long, acute but not long- 

 acuminate. 

 Culms stout; leaf -blades about 1 cm. wide; spikelets turgid. 

 Culms slender; leaf -blades not more than 6 mm. wide; 

 spikelets not turgid. 



22. P. flexile. 

 25. P. capillar e. 



23. P. Gattingeri. 



24. P. philadelphicum 



