Jones: Flora of Illinois, 22. Gramineae 65 



or sandy woods. May-Aug P. latifolium L. 



17. Spikelets 4-4.5 mm. long; nodes retrorsely bearded; woods 



throughout III., except the n.e. counties. May-July 



P. boscii Poir. 



16. Blades 6-13 mm. wide; spikelets 3-4 mm. long. 



18. Sheaths with somewhat appressed or ascending hairs; spikelets 



3.5-4 mm. long, sparsely pubescent to nearly glabrous; blades 

 glabrous or n'early so above, puberulent beneath; sandy soil. 

 May-June P. oltgosanthes Schult. 



18. Sheaths with spreading hairs, or nearly glabrous. 



19. Spikelets 3-3.5 mm. long, sparsely pubescent to nearly 

 glabrous; blades glabrous or nearly so; sandy soil. May- 

 July P. scribiierianum Nash 



19. Spikelets 3.5-4 mm. long, papillose-pilos-e; blades mere or 

 less papillose-hirsute on both surfaces, or glabrous above; 



dry sandy soil. June-July P. leibergii (Vasey) Scribn. 



15. Spikelets less than 3 mm. long. 



20. Sheaths glabrous or nearly so, or merely ciliate. 

 21. Spikelets 2.1-2.9 mm. long. 



22. Blades 12-25 mm. wide, cordate at base; spikelets short-pubes- 

 cent, 2.7-2.9 mm. long; woods, s. III. May-June 



P. commutatiim Schult. 



22. Blades 2-4 mm. wide, not cordate; spikelets sparsely pilose to 



nearly glabrous, 2.1-2 A mm. long; wooded slopes and 

 ridges, rare. Starved Rock, G. N. Jones 15728. Perhaps 



merely a glabrous form of P. linearifolium Scribn 



P. werneri Scribn. 



21. Spikelets 1.3-1.9 mm. long, puberulent or nearly glabrous. 



23. Blades usually 1.5-2.5 cm. wide, ciliate toward the base, other- 



wise glabrous; nodes glabrous or nearly so; panicle 8-25 cm. 

 long, not more than half as wide as long; moist ground, 



chiefly in s. 111., but extending northw. to Peoria Co 



P. polyanthss Schult. 



23. Blades usually 6-14 mm. wide; panicle often about as wide as 

 long. 

 24. Ligule of conspicuous hairs 3-5 mm. long; sandy soil in 

 open woods. June-Sept P. lindheimeri Nash 



24. Ligule obsolete or nearly so; sandy soil, in the s. half of 

 III. June-July P. sphaerocarpon Ell. 



20. Sheaths pubescent. 



25. Sheaths conspicuously retrorsely pilose; blades 3-7 mm. wide; 

 panicle lax, few-flowered, 5-10 cm. long; spikelets 1.9-2 mm. 

 long; wooded slopes, throughout III., except the n. counties. 

 May-July P. xalapense HBK. 



25. Sheaths not retrorsely pilose. 

 26. Spikelets 2.7-3 mm. long. 



