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



Panicle open, nearly as wide as long. 



Spikelets 1.5 mm long 39. P. LINDHEIMERI. 



Spikelets 1.1 mm long 41. P. LONGILIGULATUM. 



Sheaths pubescent. 



Ligule 1 mm long. Sheaths sparsely pilose; spikelets 1.4 mm 



long 80. P. CURTIFOLIUM. 



Ligule usually more than 1 mm long. 



Ligule 1 to 1.5 mm long. Culms and sheaths appressed- 

 pubescent; spikelets 1.5 mm long or more. 



Spikelets 2.8 to 2.9 mm long 63. P. DEAMII. 



Spikelets less than 2 mm long. 



Spikelets 1.8 to 1.9 mm long; plants bluish green. 



67. P. TSUGETORUM. 



Spikelets 1.5 mm long, nearly globular; plants olivaceous. 



69. P. ORICOLA. 

 Ligule 2 to 5 mm long. 



Spikelets 1 to 1.3 mm long; culms and sheaths softly 

 appressed-pubescent. 



Spikelets 1.2 to 1.3 mm long 40. P. LEUCOTHRIX. 



Spikelets not more than 1 mm long 



42. P. WRIGHTIANUM. 



Spikelets mostly more than 1.5 mm long, if less, pubescence 



spreading See 8. LANUGINOSA. 



13b. Ligule obsolete or less than 1 mm long. 



14a. Nodes bearded (P. scoparium may appear to be bearded) . 



Spikelets nearly 3 mm long; plants velvety-villous throughout. 



90. P. MALACOPHYLLUM. 



Spikelets rarely as much as 2.5 mm long; plants not pubescent 

 throughout. 



Spikelets 1.5 to 1.6 mm long 25. P. MICROCARPON. 



Spikelets 2 mm long or more. 



Blades all velvety. Autumnal phase usually sparingly 



branching 27. P. ANNULUM. 



Blades glabrous, or only the lower pubescent or velvety. 

 Spikelets 2 mm long; autumnal phase profusely branching. 



26. P. NITIDUM. 



Spikelets 2.2 mm long or more; autumnal phase less 

 profusely branching. 



Sheaths and upper nodes glabrous 29. P. CLUTEI. 



Lower sheaths and all nodes pubescent. 



28. P. MATTAMTJSKEETENSE. 



14b. Nodes not bearded. 



15a. Plants densely gray- velvety throughout, a viscid, glabrous 



ring below the nodes 99. P. SCOPARIUM. 



15b. Plants not gray-velvety. 



16a. Sheaths or some of them pilose or hispid. 

 Pubescence papillose-hispid. 



Spikelets ovate, pointed, 2.3 to 2.6 mm long. 



101. P. SCABRIUSCULUM. 



Spikelets obovate, obtuse, nearly 3 mm long. 



Blades about 2 cm wide 108. P. CLANDESTINUM. 



Blades not more than 6 mm wide. 



89. P. WILCOXIANUM. 

 Pubescence ascending-pilose. 



Spikelets 2.8 to 2.9 mm long 63. P. DEAMII. 



Spikelets not more than 2.5 mm long. 

 Spikelets 2 to 2.5 mm long. 



Winter blades elongate, 5 to 10 cm long; plants bluish 

 green. Spikelets 2 mm long. 



66. P. WILMINGTONENSE. 



Winter blades 1 to 3 cm long; plants olivaceous. 

 Spikelets about 2.4 mm long; panicle open, 

 branches stiffly spreading. 



64. P. COMMONSIANUM. 



Spikelets 2 to 2.1 mm long; panicle rather dense, 

 branches ascending 65. P. ADDISONII. 



