470 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



cm. long and 2 mm. wide; panicle 

 narrow, slender, loosely flowered, 10 

 to 20 cm. long; glumes about equal, 

 1 cm. long; lemma 8 mm. long; 

 awns about equal, all somewhat di- 

 vergent, 1.5 to 2 cm. long. O — 

 Low sandy soil, Indiana and Michigan 

 to Nebraska, south to Florida (Pen- 

 sacola), Mississippi, and Texas. The 

 measurements of the spikelet are 

 sometimes less than those given, 

 especially in plants attacked by smut. 

 16. Aristida barbata Fourn. 

 Havard three-awx. (Fig. 687.) 

 Perennial, forming hemispherical 

 tufts as much as 30 cm. in diameter, 

 the culms rather stiffly radiating in 

 all directions, 15 to 30 cm. long; 

 blades closely involute, mostly less 

 than 10 cm. long and 0.5 mm. thick; 

 panicles about half the length of the 

 entire plant, open, the branches di- 

 varicate!}' spreading or somewhat re- 

 flexed, mostly 3 to 6 cm. long, in 

 pairs or with short basal branchlets. 

 but without long naked base, the 

 branchlets and pedicels implicate or 

 flexuous. the whole panicle fragile at 

 maturity, breaking away and rolling 

 before the wind; glumes about equal, 

 1 cm. long; lemma gradually nar- 

 rowed into a straight or twisted 

 scaberulous beak, the entire length 

 8 to 10 mm.; awns somewhat di- 



Figure 683. 



-Aristida ramosissima, X 1. (Deam 

 18549, Ind.) 



mm. long, the second 8 to 10 mm. 

 long; lemma 6 to 9 mm. long, com- 

 pressed toward the scarcely beaked 

 summit, scabrous on the upper part 

 of the keel; awns about equal (the 

 lateral occasionally shorter), mostly 

 10 to 15 mm. long, about equally 

 divergent at an angle of as much 

 as 45°, flat and without torsion 

 at base.- O — Dry open ground, 

 Missouri (Courtney); southern Kan- 

 sas to Texas, west to Nevada and 

 southern California, southward to 

 Argentina; a common weed in the 

 American tropics; warmer parts of the 

 Old World. Originally described from 

 Ascension Island. Variable in size 

 from depauperate plants a few centi- 

 meters tall with shorter contracted 

 panicle (A. bromoides H. B. K.) to tall 

 slender plants with large open panicle 

 (A. fasciculata Torr.). 



15. Aristida intermedia Scribn. and 

 Ball. (Fig. 686.) Annual, simple or 

 branched, 20 to 40 cm. tall: blades 

 flat or involute, mostly less than 10 



r 



Figure 684. — Aristida longespica, X 1. (Vasey, D. C.) 



