22 GBAMINEAE 



15. ARISTIDA L. Thebb-awnbd Geass. 

 Annual tufted grasses, with spikelets in spike-like racemes or panicles. 

 Spikelets 1-flowered and with three scales, the third bearing three awns, 

 sometimes united at the base. 



Middle awn abruptly reflexed. 



Not spiral at base. 1. A. gracilis. 



Spiral at base. 2. A. basiramea. 

 Middle awn not abruptly reflexed. 



Awns 12"-36" long. 3. A. oHganihn. 



Awns 9'' or less long. 4. A. intermedia. 



1. A. gracilis Ell. e'-lS' high : leaves l'-9' long, flat or involute : 

 panicles simple and few-flowered, the larger 4'-5' long : second outer 

 scale 2"-3" long, sharp pointed : flowering scale 3" long, its lateral awns 

 erect, 1" long, and its central awn abruptly reflexed, 3'^-6'^ long. — 

 Occurs locally in dry sandy Qelds, five miles southeast of Grain Valley. 

 September-October. 



2. A. basiramea Engelm. Resembling the last, but first scale 3"-4''' 

 long and second if'-h" long : flowering glume b" long, its central awn 

 V-'d" long, spiral at base : lateral awns Z" long. — Dry woods along Blue 

 ^ear Martin City. 



3. A. oligantha Michx. Strongly tufted and much branching, l°-2° 

 high : panicles rather few-flowered : two lower scales awn-pointed, sub- 

 equal, &"-W long : awns spreading, the central V-Z' long, slightly 

 longer than the lateral ones. — In dry soil throughout. Often very com- 

 mon. August-October. 



4. A. intermedia S. & B. Annual, l°-2° high, erect from a decum- 

 bent and branching base : panicle strict, about 6' long : lower glumes 

 sharp-pointed, 3"-4" long, subequal : awns spreading, the central 

 g//_9// long, the lateral slightly shorter. — On sand-bars along the Mis- 

 souri Eiver at Courtney ; also at Qaindaro, Kansas. Locally abundant. 

 August-September. 



16. STIPA L. 



Usually tall grasses. Glumes three, the flowering glume coriaceous, 

 convolute around the palet and grain, with a hairy callus at base, and 

 bearing a long twisted awn articulated to the scale. 



1. S. spartea Trin. Porcupine Geass. 2°-4° tall, with long con- 

 volute leaves : panicle long-exserted, rather simple : awn h'-W long : 

 flowers early deciduous. — Common locally on rocky prairies around Lee's 

 Summit. One of our most peculiar grasses. May-June. 



17. MUHLBNBERGIA Schreb. 

 Spikelets one-flowered, borne in contracted panicles. Glumes three 

 the two outer thin and persistent, acute to awn-pointed. Flowering 

 glume acute or bearing an awn. 



