GRAMINEAE (GRASS FAMILY) 



101 



k. Leaves oblong-lanceolate to ovate-lanceolate, more than 5 mm. 

 wide, or if narrower not conspicuously elongated l. 

 L Blades more than 1.5 cm. wide 7)i. 

 in. Spikelets 3 mm. long ; at least the lower sheaths papillose-hispid 71. P. clandestinum. 

 m. Spikelets 3.5-4 mm. long. 



Nodes bearded ; plants often pubescent. 

 Blades lanceolate, thick, glabrous above, densely papillose- 

 pubescent beneath . . . . '. . . 65. P. Ravenelii. 

 Blades ovate-lanceolate, thin ; pubescence when present 



soft 72. P. Boscii. 



Nodes not bearded ; plants glabrous or nearlv so. 



Panicle spreading ; blades 2.5 cm. or more wide . . 73. P. latifoUum. 

 Panicle narrow ; blades rarely over l.S cm. wide . . 66. P. xaitihophysum. 

 I. Blades not over 1.5 cm. wide n. 

 11. Panicle narrow ; blades erect. 



Plants glabrous or nearly so 66. P. xanihophysum. 



Plants papillose-hispid. 



Spikelets not over 3 mm. long 67. P. Wilcoxianum. 



Spikelets 4 mm. long 64. P. Leibergii. 



n. Panicle spreading, about as wide as long o. 

 o. Spikelets 3 mm. long: blades l.'2-'2 dm. long. 



Blades ciliate, glaucous, smooth 59. P. mutahile. 



Blades not ciliate. green, scabrous TO. P. aculeatum. 



O. Spikelets 3.5-4 mm. long : blades not over 1 dm. long. 



Nodes bearded ; ligule 3^ mm. long 65. P. Ravenelii. 



Nodes not bearded ; ligule 1-2 mm. long. 

 Spikelets obovoid-turgid, blunt ; pubescence spread- 

 ing G3. P. Scrihnerianum 



Spikelets narrowly obovoid, subacute ; pubescence 



appressed 62. P. oligosanthes. 



g. Spikelets less than 3 Lim. long p. 

 p. Spikelets glabrous </. 



q. Spikelets not over 1.5 mm. long. 



Plants pubescent 22. P. strigonum. 



Plants glabrous, except bearded nodes 81. P. microcarpon. 



q. Spikelets 2-2.5 mm. long r. 

 r. Spikelets 2 mm. long. 



Spikelets obovoid-turgid ; culms crisp-puberulent . . 60. P. lancearium. 

 Spikelets elliiitlcal ; culms glabrous. 



Autumnal state erect, branched like a httle tree; second 



glume shorter than the fruit and sterile lemma . . 27. P. dichotomum. 

 Autumnal state topheavy-reclining ; fruit covered by 



second glume and sterile lemma 28. P. bayhulatum. 



Autumnal state widei ■ trailing: second glume and 



sterile lemma shorter than the ii-uit .... 30. P. lucidum. 

 r. Spikelets 2.5 mm. long. 



Culms 2-4 dm. high ; second glume and sterile lemma 



equaling fruit 26. P. Bickjiellii. 



Culms 5-12 dm. high: second glume and sterile lemma 



forming a point beyond the fruit 29. P. yadkiiiense. 



p. Spikelets pubescent ■«. 



s. Blades elongated, not over 5 mm. wide ; secondary panicles 

 from the base onlv, or none. 



Sheaths glabrous . " 20. P. Werneri, 



Sheaths pilose. 

 Spikelets turgid, blunt ; panicle-branches ascending ; 



culms few in a tuft \%. P. perlongum. 



Spikelets subacute ; panicle-branches spreading ; culms 



numerous in a tuft 19. P. Hyiearifoliiim. 



9. Blades usually not consjiicuously elongated ; secondary 

 panicles not at the base t. 

 t. Spikelets obovate-turgid, blunt, attenuate at base. 



Spikelets 2 mm. long 25. P. aciculare. 



Spikelets 2.5 mm. long. 

 Spikelets not papillose ; culms glabrous . . . .26. P. Bicknellii. 

 Spikelets rugose-papillo.se : culms pubescent, at least below. 

 Nodes bearded : panicle-branches ascending . , . 24. P. cottmnguineum 

 Nodes not bearded : panicle-branches spreading . . 23. P. angusti/olium. 

 t. Spikelets not attenuate at base «. 

 u. Sheaths conspicuously retrorse-pilose ; culms simple, form- 

 ing soft tufts • 21. p. aalapense. 



u. Sheaths not retrorsely pilose v. 



v. Sheaths, or all but the lowest, glabrous w. 

 w. Ligule 2-5 mm. long. 



Spikelets 2.2 mm. long 47. P. tcoparioides. 



Spikelets 1.5 mm. long. 



Panicle not more than half as wide as long : 



spikelets ellij>tic 35. P. upreium. 



Panicle about as wide as long; spikelets obovoid 36. P. Lindheimeri. 



