GRAMINEAE. 8 1 



Culms slender ; hairs on the upper surface of the leaves 



extremely long and copious. 

 Panicle 2-3 cm. long; culms minutely pubescent 



above. 34. P.filiculme. 



Panicle 4-6 cm. long ; culms hirsute above, especially 



in the panicle. 33. P. implicatum. 



Culms rather stout ; hairs on the upper surface of the 

 leaves shorter and more scattered, sometimes nearly 

 wanting. 35. P. pubescens. 



Spikelets a little more than 2 mm. long. 



36. P. Atlanttcum. 

 ** Spikelets more than 3 mm. long. 



Leaves glabrous, or sometimes pubescent beneath. 



Panicle narrow, its branches appressed. 44. P. xanthophysum, 

 Panicle open, its branches spreading. 



Sheaths glabrous, except the ciliate margins ; spikelets elliptic. 



45. P. calliphyllum. 

 Sheaths papillose-hirsute ; spikelets broadly ovoid, turgid. 



43. P. Scribnerianum. 

 Leaves pubescent on both surfaces. 



Leaves erect, rigid, thick, 3-4 mm. wide; spikelets pubescent with 



short hairs. 41. P. Wilcoxianum. 



Leaves often spreading, not thick, 5-10 mm. wide; spikelets long- 

 hirsute. 42. P. Liebergii. 

 (B) Middle leaves of the main culm more than 1.5 cm. wide, often 3 cm. in 



width, the base cordate and clasping. 

 Spikelets 2.5 mm. long or less. 



Leaves glabrous on both surfaces. 



Spikelets about 1.5 mm. long; panicle oblong and dense; culms 



simple. 47. P. polyanthes. 



Spikelets 2.5 mm. long; panicle ovoid and open ; culms branched. 

 Sheaths papillose-hispid, especially the short terminal ones on 



the branches. 52. P. clandestinum. 



Sheaths glabrous. 48. P. commutatum. 



Leaves densely villous. 38. P. viscidum. 



Spikelets 3 mm. long or more. 



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



51. P. Porterianum. 

 Nodes naked. 



Sheaths glabrous, or merely pubescent on the margins; panicle 



open, its branches spreading. 50. P. macrocarpon. 



Sheaths hispid ; panicle contracted, its branches appressed. 



44. P. xanthophysum. 



1. Panicum hians Ell. GAPING PANICUM. (I. F. f. 247.) Glabrous; culms 

 erect, 3-7.5 dm. tall, generally simple, sometimes creeping at base, smooth. 

 Leaves 7.5-12.5 cm. long, 2-6 mm. wide, acuminate, generally erect; panicle 7.5-20 

 cm. long; branches few, generally spreading, the longer ones often drooping, the 

 lower naked below the middle; spikelets about 2 mm. long; fourth scale exceeded 

 by the third and its usually empty palet which is much enlarged, generally forc- 

 ing the spikelet wide open. In moist ground, N. Car. to Mo., south to Fla. and 

 Tex. Aug.-Sept. 



2. Panicum verrucosum Muhl. WARTY PANICUM. (I. F. f. 278.) Culms 

 erect or decumbent, slender, generally much branched at base. Sheaths glabrous, 

 much shorter than the internodes; leaves 5-17.5 cm. long, 2-8 mm. wide, erect or 

 ascending, glabrous, rough on the margins; panicle 7.5-30 cm. long, its lower 

 branches 5-15 cm. long, naked below, strict and ascending, or lax and spreading; 

 spikelets about 1.5 mm. long, elliptic, acutish, borne in pairs along the branches, 

 the first scale about one-quarter as long as the warty second and third, the fourth 

 scale apiculate. Moist soil, Mass, to Fla., west to La., mostly near the coast. 

 July-Sept. 



3. Panicum capillare L. WITCH-GRASS. TUMBLE WEED. (I. F. f. 274.) 

 Culms erect or decumbent, 3-6 dm. tall, simple or sometimes sparingly branched. 

 Sheaths papillose-hirsute; leaves 1.5-3 dm. long, 6-16 mm. wide, pubescent; 

 terminal panicle 2-3.5 dm. l n g> lower branches 1.5-2.5 dm, long; lateral pani- 



