348 American Midland Naturalist Monograph No. 7 



diffuse, often half the length of the plant; sheaths copi- 

 ously villous; fields, roadsides, and waste places, com- 

 mon. July-Oct. Witch Grass P. capillare L. 



12. Spikelets elliptical, obtuse, 1.3-2.2 mm long. 



13. Panicles 12-20 cm wide, delicate, relatively few- 

 flowered; blades 2-6 mm wide, villous on both sides; 

 roadsides and waste places, local. July-Oct. [P. 

 tuckermani Fern.] P. pJdladclphicurn Bernh. 



13. Panicles narrower; blades 6-10 mm wide, nearly or 

 quite glabrous; plants much branched, with many 

 axillary panicles; moist sandy soil, along roads, in 

 fields, or along streams; s. and central 111., extend- 

 ing northward to Henry Co. Sept. -Oct 



.- P. gattingeri Nash 



1. Spikelets pubescent or puberulent (occasionally only sparsely so). 



14. Spikelets 3 mm or more in length; sheaths more or less pubes- 

 cent or ciliate. 



15. Blades 1.5-4 cm wide, ciliate, otherwise glabrous or 

 nearly so. 



16. Spikelets 3.4-3.8 mm long; nodes glabrous or puberu- 

 lent; rocky or sandy woods. May-Aug 



- P. latifoliuni L. 



16. Spikelets 4-4.5 mm long; nodes retrorsely bearded; 



woods throughout 111., except the n.e. counties. May- 

 July P. boscii Poir. 



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



17. Sheaths with appressed or ascending hairs; spikelets 



sparsely pubescent to nearly glabrous; blades glabrous 

 or nearly so above, puberulent beneath; sandy soil, 

 local. May-June P. oligosanthes Schult. 



17. Sheaths with spreading hairs, or nearly glabrous. 



18. Spikelets sparsely short-pubescent to nearly gla- 

 brous; blades glabrous or nearly so; sandy soil, 



common. May-July P. scrihnerianum Nash 



18. Spikelets pilose; blades more or less papillose-hirsute 

 on both surfaces, or glabrous above; dry sandy 



soil, occasional. June-July 



P. leihergii (Vasey) Scribn. 



14. Spikelets less than 3 mm long. 



19. Sheaths glabrous or nearly so, or merely ciliate (or the 

 lower internodes and sheaths sometimes pubescent in 

 P. lindheimeri) . 

 20. Spikelets 2.1-2.9 mm long. 



21. Blades 12-25 mm wide, cordate at base; spikelets 

 short-pubescent, 2.7-2.9 mm long; woods, s. 111. 

 May-June P. commutatum Schult. 



