MANUAL OF THE GRASSES OF THE UNITED STATES 439 



Stipa neesiana Trin. and Rupr. Related to S. leucotricha but with 

 shorter lemma with thickened erose crown. % — Ballast, Mobile. 

 Ala.; South America. 



Stipa brachychaeta Godr. Blades firm, flat, or loosely involute; 

 panicle narrow, open, the few spikelets on slender pedicels; glumes 8 

 mm long; lemma 5 mm long, brown, pubescent in lines; awn 12 mm 

 long. 01 —Ballast near Portland, Oreg. ; Argentina. 



Stipa elegantissima Labill. Tufted perennial; foliage scant; panicle com- 

 monlv half the height of the plant, the filiform spreading branches conspicuously 

 feathery; spikelets purple, long-awned. 01 — Sometimes cultivated for orna- 

 ment; Australia. 



Stipa pennata L. Tufted perennial; blades elongate, involute; panicle few- 

 flowered, the large spikelets with awns 25 to 35 cm long, conspicuously feathery 

 above the bend. 01 — Sometimes cultivated for ornament; Europe. 



Stipa tenacissima L. Esparto. Tufted perennial with tough branching base; 

 blades elongate, involute, tomentose at base and with erect auricles 3 to 10 mm 

 long; panicle narrow, dense; awns 4 to 6 cm long, feathery below the bend. 01 — 

 Sometimes cultivated for ornament; Spain and Algeria, where it is gathered for 

 making paper and cordage. 



85. ARISTIDA L. Three-awn 



Spikelets 1-flowered, the rachilla disarticulating obliquely above 

 the glumes; glumes equal or unequal, narrow, acute, acuminate, or 

 awn-tipped; lemma indurate, narrow, terete, convolute, with a hard, 

 sharp-pointed, usually minutely bearded callus, terminating above 

 in a usually trifid awn (the lateral divisions reduced or obsolete in 

 Section Uniseta), the base sometimes undivided, forming a column. 

 Annual or perennial, mostly slender tufted grasses, with narrow, 

 frequently convolute blades and narrow or sometimes open panicles. 

 Type species, Aristida adscensionis L. Name from Latin arista, awn. 



The species are of distinctly minor importance for forage except in 

 the Southwest, where several, such as A. longiseta, are eaten by 

 stock before the flowers are produced. The ripe fruits of several 

 species are troublesome to stock on the plains because of the sharp 

 hard points. These fruits are produced sometimes in vast numbers 

 and are carried far and wide by the wind in open country. Aristida 

 adscensionis is one of the annuals that make up the "six-weeks" 

 grasses of the Southwest. 



Lemma articulate with the column of the awns; awns nearly equal. 



Section 1. Arthratherttm. 



Lemma not articulate. 



Lateral awns minute (less than 1 mm long) or wanting. Section 2. Uniseta. 



Lateral awns more than 1 mm long (rarely obsolete in A. ramosissima) , usually 



well developed - Section 3. Chaetaria. 



Section 1. Arthralherum 

 Plants annual. 



Column very short 1. A. desmantha. 



Column 10 to 15 mm long, twisted 2. A. tuberculosa. 



Plants perennial. 



Culms pubescent 3. A. californica 



Culms glabrous 4. A. glabrata 



Section 2. Uniseta 



Awn (column) tiwsted at base 7. A. orcuttiana 



Awn not twisted. 



Branches of panicle distant, spreading, mostly more than 5 cm long, naked 



at base; awn straight or abruptly divergent 5. A. ternipes. 



Branches of panicle short, approximate, 3 to 5 cm long, floriferous nearly to 

 base; awn curved and flexuous, .,„,-.. ,. 6, A. flqridana 



