igo REPORT OF NEW JERSEY STATE MUSEUM. 



aa. Perennial. 



b. Spikelets short pedicelled along one side of the rachis, forming spike- 

 like racemes. P. hcmitouion, p. 194 

 bb. Spikelets in open, rarely contracted panicles. 



c. Basal leaves different from culm leaves, usually forming winter 

 rosettes. 

 d. Spikelets glabrous. 



e. Spikelets 3mm. or more long, strongly nerved. 

 f. Spikelets pointed, blades elongated. 



P. depaiiperatum, p. 198 

 //. Spikelets blunt, blades not elongated, 3.2-3.3 mm. ; 

 long sheaths or some of them hispid. 



P. scribnerianum, p. 209 

 ee. Spikelets less than 3mm. long. 



/. Second glume and sterile lemma exceeding the fruit 

 and pointed beyond it, spikelets 2.2-2.9 mm. long. 

 g. Spikelets elliptic, fruit 2 mm. long. 



P. aculeatiim, p. 210 

 gg. Spikelets ovate, broadest below the middle, 2 mm. 

 or less. 

 /;. Sheaths (at least the secondary) hispid. 



P. scabrinsctilum, p. 210 

 /;/;. Sheaths glabrous. P. cryptanthum, p. 210 



ff. Second glume and sterile lemma, not pointed beyond 

 the fruit. 



g. Ligule 2-3 mm. long. P. spretiim, p. 202 



gg. Ligule obsolete. 



h. Spikelets 1.5 mm. long or less. 



i. Nodes bearded. P. microcarpon, p. 200 



it. Nodes not bearded. 



j. Spikelets 1.5-1.6 mm. blades 50-80 mm. 

 long, 4-7 mm. wide. 



P. caeriilcscens, p. 200 

 ij. Spikelets 1.2-1.4 mm., blades not over. 

 30 mm. long, 1.5-3 nim. wide. 



P. ensifolhini, p. 207 

 /;;. Spikelets 2mm. long or more. 



k. Culms soon prostrate, vine-like, 

 branches divaricate. 



P. lucidum, p. 200 

 kk. Culms not vine-like, branches not 

 divaricate. 



/. Nodes glabrous ; autumnal form 



upright. P. dichotomitm, p. 199 



//. Nodes, at least the lowest, 



usually bearded, autumnal form, 



top-heavy and reclining. 



P. barbulatum, p. 200 



