118 POACEAE 



19. Aristida gracilis Ell. Stems densely tufted, 1.5-6 dm. tall, slender, finally 

 more or less branched : leaf-sheaths equalling or shorter than the internodes, glabrous, 

 or the lower ones sparingly pubescent ; blades 3-12 cm. long, 1 mm. wide or less, erect, 

 flat : panicle 5-15 cm. long, its short branches appressed : spikelets 5-7 mm. long, the 

 2 outer scales 1-nerved, usually awn-pointed, the first equalling or a little shorter than the 

 second, sparingly hispidulous, the flowering scale 5-6 mm. long, frequently barred or 

 spotted with black, more or less hispidulous, especially on the keel, the central awn 

 spreading, 6-10 mm. long, rarely longer, the lateral awns erect, 1-3 mm. long, occasion- 

 ally longer. 



In dry soil, Vermont to Illinois, Kansas, Florida and Texas. Summer and fall. 



20. Aristida intermedia Scribn. & Ball. Stems slender, finally branching, 3-8 

 dm. tall : leaf-sheaths glabrous or sparsely hirsute ; blades 5-15 cm. long, 2 mm. wide or 

 less, erect, involute : panicle 2-4 dm. long, slender, its branches appressed : spikelets 8-10 

 mm. long, the empty scales manifestly awned, altout equal, the flowering scale strongly his- 

 pidulous above the middle, equalling or exceeding the empty scales, the awns spreading, 

 the middle one 15-25 mm. long, the lateral ones shorter. 



In sandy soil, Iowa to Mississippi and Texas. Summer and fall. 



21. Aristida Chapmani^na Nash. Stems densely tufted, 7-10 dm. tall, finally more 

 or less branched : leaf-bladesl-2dm. long, 1.5-2.5 mm. broad, flat, long-acuminate : panicle 

 2-4 dm. long, the branches short and appressed : spikelets 6-8 mm. long, rather crowded 

 on the branches, the 2 outer scales 1-nerved, or the first rarely with faint lateral nerves, 

 the first one shorter than the second, usually strongly hispidulous, the flowering scale about 

 5 mm. long, glabrous or sparingly hispidulous on the upper part of the keel, the central awn 

 widely spreading, at right angles to the scale, 1.8-2.5 cm. long, the lateral awns erect, 

 usually a little more than j as long as the central awn, rarely shorter. 



In dry sandy soil, North Carolina to Florida and Mississippi. Fall. 



22. Aristida purpurdscens Poir. Stems tufted, 3-8 dm. tall, usually simple, or 

 occasionally branched : leaf-sheaths smooth and glabrous, or the lower ones sometimes 

 pubescent ; blades 0.5-2 dm. long, 1-2 mm. wide, flat, long-acuminate : panicle 1.5-3 dm. 

 long, its branches appressed and usually short : spikelets 9-12 nmi. long, rarely a little 

 smaller, usually crowded, the 2 outer scales 1-nerved, sometimes awn-pointed, the first 

 one usually exceeding the second, occasionally equalling it, hispidulous, the flower- 

 ing scale 6-8 mm. long, glabrous or sparingly hispidulous, the awns more or less spreading, 

 especially the central one which is 1.5-2.5 cm. long, the lateral awns from f as long to- 

 nearly equalling it. 



In dry soil, Massachusetts to Minnesota, Florida and Texas. Fall. 



23 Aristida paliistris ( Chapm. ) Vasey. Stems densely tufted, 8-12 dm. tall, firm 

 and hard at the base : leaf-blades 2-4 dm. long, 2-3 mm. wide : panicle 2-5 dm. long,_its 

 branches closely appressed, the longer 5-7 cm. long : spikelets 10-12 mm. long, the first 

 scale prominently 2-3-nerved, strongly liispidulous, from a little shorter than to slightly 

 exceeding the second, the flowering scale 8-9 mm. long, smooth and glabrous, the callus 

 fully 1 mm. long, sparsely pilose, the central awn widely spreading, 1.5-3 cm. long, the 

 lateral awns erect or nearly so, from f as long as to nearly equalling it. 



In swamps and wet places, Florida to Louisiana. Late summer and fall. 



24. Aristida lanosa Muhl. Stems 8-14 dm. tall, simple, rather stout: leaf-sheaths 

 confined to the lower part of the stem, densely woolly pubescent ; blades 3-5 dm. long, 2-7 

 mm. wide, flat : panicle 4-6 dm. long, its axis villous at the nodes, its lower branches dis- 

 tant, ascending, 8-12 cm. long : spikelets 12-17 mm. long, the 2 outer scales 1-nerved, the 

 first much exceeding the second, the flowering scale 8-10 mm. long, the central awn widely 

 spreading, 1.5-2.5 cm. long, the lateral awns erect or ascending, about ^ as long. 



In dry thickets, Delaware to Florida, and Texas. Fall. 



25. Aristida spiciformis EU. Stems tufted, 4-10 dm. tall, simple : leaf-sheaths 

 overlapping on the lower part of the stem ; blades 1-3 dm. long, flat, or involute when dry, 

 3-5 mm. wide : panicle 12-20 cm. long, oblong, very dense : spikelets densely crowded, 

 the 2 outer scales 1-nerved, the first scale about ^ as long as the .second which is about 

 1 cm. long, the former with an awn longer than its body, the latter bearing an awn of 

 about equal length, the flowering scale, exclusive of the awns and including the 2 mm. long 

 callus, about 6 mm. long, the awns united below into a twisted flexuous column 1.5-2.5 cm. 

 long, the free portion of the awns spreading or ascending, tlie central awn 2.5-3.5 cm. long, 

 the lateral ones a little shorter. 



In moist or flat pine lands, South Carolina to Florida. Summer and fall. 



26. Aristida patula Ciiapm. Stems tufted, 1-1.5 m. tall, simple, the leaves confined 

 to the lower part of the stem : leaf-sheaths overlapping, smooth, usually with a j)ubescent 



