HITCHCOCK — REVISIONS OF NORTH AMERICAN GRASSES. 157 



Blades linear-lanceolate to Hn3ar, narrow; bristles below all the spikelets. 

 Chaetochloa proper. 

 Bristles below each spikelet numerous, at least more than 5. Panicle dense, 

 cylindric, spikelike. 



Plants annual; spikelets 3 mm. long 5. C. lutescens. 



Plants perennial; spikelets mostly 2 to 2.5 mm. long 6. C. geniculata. 



Bristles below each spikelet I, or, by the abortion of the spikelets, 2 or 3. 

 Bristles more or less retrorsely scabrous. 



Plants perennial; spikelets globose or nearly so 7. C. tenax. 



Plants annual; spikelets not globose. 



Spikelets about 2 mm. long .8. C. verticillata. 



Spikelets about 1.5 mm. long. 

 Panicles usually green, rarely as much as 8 cm. long, less than 5 mm. 



thick, the bristles 2 to 3 mm. long 9. C. scandens. 



Panicles usually purple, as much as 15 cm. long and 1 cm. thick, the 



bristles about 1 cm. long 10. C. tenacigsima. 



Bristles antrorsely scabrous only. 

 Plants annual. 

 Fertile lemma at maturity finely cross-lined or nearly smooth. 



Panicle loosely flowered, tapering above 11. C. grisebachii. 



Panicle compactly flowered, sometimes interrupted at base. 



Plants as much as 3 meters tall. Bristles 1 to 2 cm. long; fertile lemma 



smooth or nearly so 12. C. magna. 



Plants mostly less than 1 meter tall. 



Axis of panicle scabrous but not villous 13. C. ambigua. 



Axis of panicle villous. 



Panicle cylindric, tapering aboA^e, green; spikelet falling entire. 



14. C. viridis. 

 Panicle lobed or interrupted, often large and heavy, purple or 



yellow; fruit deciduous from glumes and sterile lemma. ^_ 



15. C. italica. 

 Fertile lemma coarsely transversely rugose. 



Axis of panicle thickly clothed with white stiff hairs 2 mm. long. 



16. C. longipila. 

 Axis of panicle villous, the hairs about 1 mm. long. 



Panicle densely flowered, cylifldric. Sheaths scabrous. 



17. C. corrugata. 

 Panicle loosely flowered. 



Blades scabrous but not hispid 18. C. liebmaimi. 



Blades sparsejy hispid 19. C. latifolia. 



Plants perennial. 

 Spikelets 3 mm. long. 



Blades, scabrous 20. C. macrosperma. 



Blades villous 21. C. villosissima. 



Spikelets 2 to 2.5 mm. long. 

 Panicle attenuate at apex. 

 Blades linear-lanceolate, more than 5 mm. broad; panicle interrupted 



or branched, the branches 1 to 3 cm. long 22. C. setosa. 



Blades slender, mostly less than 5 mm. broad; panicle slender, very 



narrow 23. C. rariflora. 



Panicle often narrowed toward the summit but not attenuate. 

 Branches of primary panicle stiffly ascending, of about equal length 

 except toward the summit; panicle yellowish or brownish, the 

 bristles 1 to 2 cm. long 24. C. vulpiseta. 



