MANUAL OF THE GRASSES OF THE UNITED STATES 641 



Spikelets 1.5 mm. long 41. P. lindheimeri. 



Spikelets 1.1 mm. long 43. P. longiligulatum. 



Sheaths pubescent. 



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



83. 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 66. P. deamii. 



Spikelets less than 2 mm. long. 



Spikelets 1.8 to 1.9 mm. long; plants bluish green. 



70. P. TSUGETORUM. 



Spikelets 1.5 mm. long, nearly globular; plants olivaceous. 



72. P. ORICOLA. 

 Ligule 2 to 5 mm. long. 

 Spikelets 1 to 1.3 mm. long; culms and sheaths softly appressed-pubes- 

 cent. 



Spikelets 1.2 to 1.3 mm. long 42. P. leucothrix. 



Spikelets not more than 1 mm. long 44. 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. 



93. P. MALACOPHYLLUM. 



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



Spikelets 1.5 to 1.6 mm. long 27. P. microcarpon. 



Spikelets 2 mm. long or more (sometimes 1.8 mm. in P. mundum). 

 Blades all velvety; autumnal phase usually sparingly branching. 



29. P. ANNULUM. 



Blades glabrous, or only the lower pubescent or velvety. 



Autumnal phase profusely branching, the branchlets forming large 

 clusters at the nodes of the primary culms. Upper sheaths usu- 

 ally glandular spotted 28. P. nitidum. 



Autumnal phase sparingly branching. 

 Lower sheaths or blades velvety-pilose. 



Sheaths and upper nodes glabrous 31. P. clutei. 



Lower sheaths and all the nodes pubescent. 



30. P. MATTAMUSKEETENSE. 



Lower sheaths ascending-pilose or glabrate, not velvety, the blades 

 glabrous or papillose-ciliate toward the base. 



105. P. MUNDUM. 



14b. Nodes not bearded. 



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



the nodes 102. P. scoparium. 



15b. Plants not gray-velvety. 



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



Pubescence papillose-hispid, papillose-pilose, or sometimes glabrate. 

 Spikelets glabrous, ovate, pointed beyond the fruit, the first glume 



short, broadly acute 106. P. scabriusculum. 



Spikelets pubescent or pilose, obovate or elliptic, the first glume 

 longer, acute. 

 Blades about 2 cm. wide, often as much as 3 cm.; fruit distinctly 



shorter than the spikelet 113. P. clandestinum. 



Blades less than 15 mm. wide; fruit nearly as long as the spikelet. 



Blades flat, 8 to 15 mm. wide 104. P. recognitum. 



Blades involute-acuminate, not more than 6 mm. wide. 



92. P. wilcoxianum. 

 Pubescence ascending-pilose. 



Spikelets 2.8 to 2.9 mm. long 66. 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 69. P. wilmingtonense. 



Winter blades 1 to 3 cm. long; plants olivaceous. 



Spikelets about 2.4 mm. long; panicle open, branches stiffly 

 spreading 67. P. commonsianum. 



