GRAMINEAE 19 



Hairs on the lower surface soft and copious. 

 Spikelets 1.5 mm. long. 24. P. Tennesseense. 



Spikelets 2.5 mm. long. 25. P. scoparium. 



Hairs on the lower surface long and stiff. 

 Spikelets 1.5 mm. long. 

 Stems slender : hairs on the upper surface of the leaf -blades 



extremely long and copious. 21. P. implicatum. 

 Stems rather stout : hairs on the upper surface of the leaf- 

 blades more scattered, sometimes nearly wanting. 



22. P. unciphyllum. 

 Spikelets a little more than 2 mm. long. 



23. P. Atlaniicum. 

 ** Spikelets exceeding 3 mm. in length. 



Panicle narrow, its branches appressed : spikelets usually few. 



27. P. xanlhophysum. 

 Panicle open, its branches spreading : spikelets usually numerous. 



26. P. Scribnerianum. 

 b. Middle leaf-blades of the main stem 1.5 cm. wide, often 3 cm., the base 



cordate and clasping. 

 Spikelets 2.5 mm. long or less. 

 Leaf-blades glabrous on both surfaces. 

 Spikelets about 1.5 mm. long: panicle oblong and dense: stems 



simple. 29. P. polyanlhes. 



Spikelets 2.5 mm. long : panicle ovoid and open : stems branched. 

 Sheaths pubescent. 

 I,eaf-blades ciliate at the base : spikelets 3 mm. long or more. 



35. P. clandestinum. 

 I^eaf-blades naked at the base : spikelets less than 3 mm. long. 



36. P. decoloratum. 

 Sheaths glabrous. 30. P. commutatum. 



I^af-blades densely villous. 25. P. scoparium. 



Spikelets 3 mm. long or more. 

 Nodes naked. 

 Sheaths hispid : panicle contracted, its branches appressed. 



27. P. xanlhophysum. 

 Sheaths glabrous, or somewhat pubescent on the margins : panicle 



open, its branches spreading. 32. P. macrocarpon. 



Nodes manifestly and copiously barbed : spikelets 4.-5 mm. long. 

 Lower surface of the leaf -blades paler, glabrous. 



33. P. Porlerianum. 

 Lower surface of the leaf-blades pubescent, as are also the sheaths 

 and stems. 34. P. pubifoHum. 



1. Fanlcum verrucosum Muhl. WarTy Panicum. (Man. p. 81 ; 

 I. F. f. 278.) Moist soil, Mass. to Fla., and La., mostly near the coast. 

 — Pennsylvania : Delaware, Tinicum ; Bucks, Bristol. 



2. Panicum capillare L. Witch Grass. Tumbi,e-weed. (Man. p. 

 81 ; I. F./. 274.) In dry soil, common as a weed in cultivated fields. 

 N. S. to B.C., Fla., Tex. and Nev. — Pennsylvania: Delaware; Ches- 

 ter ; Lancaster ; Dauphin ; Northampton ; Erie ; Jefferson ; 

 Philadelphia. Franklin. 



3. Fanicum Phlladelphicum Bernh. Wood Panicum. (Man. p. 82 ; 

 I. F. f. 277.) In dry woods and thickets, N. B. to Ga., west to Mo. — 



