MANUAL OF THE GRASSES OF THE UNITED STATES 629 



Spikelets not subsecund, the panicle loose and open 22. P. ovinum. 



Plants pubescent, at least on the lower half. 



Spikelets about 2.4 mm., rarely only 2.1 mm., or as much as 2.8 mm., long; 

 vernal blades 7 to 12 cm. long; autumnal blades not falcate. 



21. P. ARENICOLOIDES. 



Spikelets not more than 2 mm. long; vernal blades 4 to 6 cm. long; autumnal blades 

 much crowded, falcate 14. P. aciculare. 



4. Bicknelliana 



Spikelets 2.5 to 2.8 mm. long; blades not more than 9 mm. wide 24. P. bicknellii. 



Spikelets 3 mm. long; blades as much as 12 mm. wide 25. P. calliphyllum. 



5. Nudicaulia 



A single species 26. P. nudicaule. 



6. Dichotoma 



la. Nodes, at least the lower, bearded. 

 Spikelets 1.5 to 1.6 mm. long, glabrous (occasional individuals with pubescent spikelets). 



27. P. MICROCARPON. 



Spikelets 2 mm. long or more. 

 Spikelets glabrous, 2 mm. long. 



Autumnal phase erect, branched like a little tree; primary blades rarely more than 



5 mm. wide 33. P. dichotomum. 



Autumnal phase top-heavy-reclining; primary blades 6 to 10 mm. wide. 



34. P. BARBULATUM. 



Spikelets pubescent. 



Blades all velvety; autumnal phase branching from upper nodes. 



29. P. ANNUL ATUM. 



Blades glabrous or nearly so, or only the lowermost velvety. 



Primary blades mostly erect; autumnal phase sparingly branching, the branches 



erect; blades and panicles not much reduced 32. P. boreale. 



Primary blades spreading; blades and panicles of autumnal phase much reduced. 

 Spikelets 2 mm. long; autumnal phase profusely branching.... 28. P. nitidum. 

 Spikelets 2.2 mm. long or more; autumnal phase less profusely branching. 



Sheaths and upper nodes glabrous 31. P. clutei. 



Lower sheaths and all nodes pubescent 30. P. mattamuskeetense. 



lb. Nodes not bearded. 

 2a. Spikelets pubescent. 



Culms erect, never becoming vinelike. 

 Primary blades spreading; panicles purplish; fruit exposed at summit. 



31. P. CLUTEI. 



Primary blades erect; panicles green; fruit covered (woods forms with spreading 



blades may be distinguished from P. dichotomum by pubescent spikelets. 2.2 mm. 



long) 32. P. BOREALE. 



Culms soon prostrate, vinelike, the branches divaricate. 



Plants bright green, culms lax; spikelets not more than 2.1 mm. long. 



38. P. LUCIDUM. 



Plants grayish green, culms stiff; spikelets 2.5 mm. long 39. P. sphagnicola. 



2b. Spikelets glabrous. 

 Culms soon prostrate. 



Plants bright green, culms lax; spikelets not more than 2.1 mm. long. 



38. P. LUCIDUM. 



Plants grayish green, culms stiff; spikelets 2.5 mm. long 39. P. sphagnicola. 



Culms erect, or the autumnal phase topheavy, never prostrate. 



Spikelets not more than 1.6 mm. long; panicles narrow; plants glaucous bluish green. 



37. P. CAERULESCENS. 



Spikelets 2 mm. long or more; panicles open. 



Blades erect, firm; spikelets turgid, strongly nerved; plants grayish olive green. 



36. P. ROANOKENSE. 



Blades spreading; spikelets not turgid. 



Spikelets 2.2 mm. long or more, pointed; sheaths bearing pale glandular spots. 



35. P. YADKINENSE. 



Spikelets not more than 2 mm. long, not pointed. 



Autumnal phase erect, branched like a little tree; primary blades rarely more 

 than 5 mm. wide; second glume shorter than fruit and sterile lemma. 



33. P. DICHOTOMUM. 



