64 American Midland Naturalist Monograph No. 2 



rounded at the apex; plants annual, mostly glabrous; spikelets 



2.5 mm. long; fields and waste places, common. Aug. -Oct 



P. dichotomiflorum L. 



8. First glume more than one fourth the length of the spikelet; plants 



perennial. 



9. Spikelets 1.5-1.6 mm. long; blades 10-12 cm. long, 8-15 mm. 

 wide, ciliate at base, otherwise glabrous; panicle 8-12 cm. long; 

 stem-nodes densely bearded with reflexed hairs; wet ground, 

 local. June-Aug P. microcarpon Muhl. 



9. Spikelets 2-2.5 mm. long. 



10. Pedicels about half the length of the spikelets; panicles 10-30 

 cm. long, the spikelets subsecund; plants in dense turfts; 



moist ground. July-Oct. Munro Grass 



P. agrostoides Spreng. 



10. Pedicels longer than the spikelets, which are not at all secund; 

 panicles 4-12 cm. long. 



11. Sheaths bearing pale glandular spots, the margins gla- 

 brous; blades 8-11 mm. wide; spikelets 2.3-2.5 mm. 

 long, pointed; moist woods and thickets, s. 111. June- 

 July P. yadhnense Ashe 



11. Sheaths not spotted, the margins pubescent; blades 4-8 

 mm. wide; spikelets 2 mm. long, not pointed; open 

 woods, more common in s. 111., but extending nortbw. 



to Peoria Co. May-July. [P. barbulatum Michx.} 



P. dichotomum L. 



7. Sheaths pubescent. 



12. Spikelets lanceoloid, acuminate; panicle diffuse, often half the length 

 of the plant; sheaths copiously villous. 

 13. Spikelets 2-2.5 mm. long; fields, roadsides, and waste places, 

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



13. Spikelets 2.5-3 (-3.3) mm. long; moist sandy soil, occasional; w. 



111. July-Sept P. harbipulvinatuin Nash 



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



14. Panicles 12-20 cm. wide, delicate, relatively few-flowered; blades 

 2-6 mm. wide, villous on both sides; roadsides and waste 



places. July-Oct. [P. tuckermani Fern.} 



P. philadelphicum Bernh. 



14. Panicles narrower; blades about 1 cm. wide, nearly or quite gla- 

 brous; plants much branched, with many axillary panicles; 

 moist sandy soil, along roads, in fields, or along streams, s. and 



centr. III., extending northw. to Henry Co. Sept. -Oct 



P. gattingeri Nash 



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



15. Spikelets 3 mm. or more in length; sheaths more or less pubescent or 

 ciliate. 

 16. Blades 1.5-4 cm. wide, ciliate, otherwise glabrous or nearly so. 



17. Spikelets 3.4-3.8 mm. long; nodes glabrous or puberulent; rocky 



