POACEAE 119 



ring at the summit ; blades 2-6 dm. long, 3-5 mm. wide, flat, glabrous, smooth, even on 

 the margins : panicle 4-6 dm. long, its branches widely spreading, rough, divided, the 

 larger ones 2-3 dm. long : spikelets on short pedicels, the 2 outer scales 1 -nerved, more or 

 less awned, the first one 11-14 mm. long, usually exceeding the second, rarely equalling 

 or a little shorter than it, the flowering scale 1-1.5 cm. long, smooth and glabrous, the awns 

 erect or nearly so, the central one 2-3 cm. long, the lateral ones - f as long. 

 In dry sandy soil, peninsular Florida. Summer and fall. 



27. Aristida tuberculosa Nutt. Stems tufted, 2-5 dm. tall, branched : leaf -sheaths 

 shorter than the internodes, the lower ones pubescent ; blades 8-20 cm. long, 1.5-2.5 mm. 

 wide, flat : panicle 1-2 dm. long, its branches erect or ascending, the larger ones 6-10 cm. 

 long : spikelets on short pedicels, the 2 outer scales 1 -nerved, awn-pointed, the body of the 

 first shorter than that of the second which, exclusive of the awn, is about 2 cm. long, the 

 flowering scale, exclusive of the awns and including the 2-3 mm. long callus, 12-15 mm. 

 long, the awns united at the base into a spiral column 6-20 mm. long which is articulated to 

 the scale, the free portion finally reflexed and sometimes coiled at the base, the central awn 

 3.5-5 cm. long, the lateral ones a little shorter. 



In sandy soil, especially along sea beaches, Massachusetts to Georgia ; also in the interior in 

 Minnesota, Wisconsin and Illinois. Summer and fall. 



28. Aristida desmantha Trin. & Rupr. Stems 4-8 dm. tall, branching : lower leaf- 

 sheaths pubescent; blades 6-30 cm. long, 1.5-2 mm. wide, flat, or involute when dry: 

 panicle 1.5-2 dm. long, its branches erect or nearly so, the lower ones 6-8 cm. long : spike- 

 lets on short pedicels, the 2 outer scales awned, 1-nerved, the first one sometimes with 2 

 or 3 lateral nerves on each side, the first usually equalling or shorter than the second 

 which is 12-14 mm. long, exclusive of the awn, rarely exceeding it, the flowering scale, 

 exclusive of the awns, 8-10 mm. long, the awns united at the base into a usually spiral 

 column 2 mm. long or less which is articulated to the scale, the free portion finally reflexed 

 and usually coiled at the base, the central awn 2.5-3 cm. long, the lateral ones a little 

 shorter. 



In dry soil, the Indian Territory and Texas. Summer. 



53. ORTACHNB Nees. 



Tall usually slender grasses, with flat or involute leaf-blades and terminal panicles. 

 Spikelets 1 -flowered : empty scales narrow, acuminate, usually awn -pointed : flowering scale 

 narrow, merging into the single terminal awn. Stamens 3. Styles distinct. Stigmas 

 plumose. 



1. Ortachne Floridana (Chapm. ) Nash. Stems 6-10 dm. tall, simple: leaf-blades 

 2-3 dm. long, involute, at least when dry, about 1 mm. in diameter : panicle 2-3 dm. long, 

 its branches ascending, the larger ones 8-14 cm. long : spikelets 9-11 mm. long, the 2 outer 

 scales 1-3-nerved, the first from a little shorter than to somewhat exceeding the second, 

 the flowering scale 1.5-2 cm. long, compressed, curved at the summit, gradually tapering 

 into the single awn which is 14-18 mm. long. [Aristida Floridana (Chapm.) Vasey.] 



In dry places, Key West, Florida. Spring to fall. 



54. STIPA L. 



Tufted grasses, with convolute or flat leaf-blades and terminal contracted or open, often 

 slender, panicles. Spikelets narrow, 1-flowered, usually few and large, or sometimes 

 smaller and numerous. Scales 3, the 2 outer empty, persistent, narrow, keeled, acute, 

 rarely awned, the third scale tightly convolute about the 2-nerved or 2-keeled palet and 

 the perfect flower, rigid, narrow, the apex usually attenuated into a more or less geniculate 

 awn (or rarely 2-toothed or shortly 2-cleft, with the awn strict and arising between the 

 teeth) which is often spiral or twisted at the base, and generally deciduous at the articula- 

 tion to the scale, rarely not articulated and persistent. Stamens 3, or rarely fewer, the 

 anthers very often barbellate at the apex. Styles short, distinct. Stigmas plumose. 



Flowering scale abruptly contracted above into a smooth cylindric appendage over 



1 mm. long and hairy at the apex. 1. S. leucotricha. 



Flowering scale not thus appendaged : 



About 1 cm. long : empty scales 8-12 mm. long. 2. . avenacea. 



Exceeding 1.5 cm. in length : empty scales 1.5 cm. long or more. 3. S. avenaceoides. 



1. Stipa leucotricha Trin. Stems tufted, 3-5 dm. tall, erect : leaf-sheaths glabrous, 

 or sparingly pubescent, the upper one often enclosing the base of the panicle ; blades rather 

 sparingly pubescent with short spreading hairs, 2 dm. long or less, 2-3 mm. wide : panicle 

 1-1.5 dm. long, its branches erect : spikelets 15-18 mm. long, exclusive of the awn ; 



