94 FLORA. 



Stamens 3. Styles distinct. Stigmas plumose. Grain free, tightly enclosed in 

 the scale. [Latin, from arista, an awn.] About 100 species, in the warmer 

 regions of both hemispheres. Besides the following, some 25 others occur in the 

 southern and western parts of N. Am. The English name Three-awned Grass 

 is applied to all the species. 



Awns not articulated to the scale. 

 Central awn coiled at the base. 



First scale usually equalling; or sometimes slightly shorter than the second scale, 



which is generally 7-9 mm. long. i. A, dichotoma. 



First scale much shorter than the second (often but little more than one-half as 



long), which is 10-15 mm. long. 



Lateral awns short, straight and erect, 1-2 mm. long, the central awn 

 usually more than five times their length, its straight portion 5-8 mm. 

 long. 2. A. Curtissii, 



Lateral awns more or less spreading, usually a little spiral at the base, the 

 central awn from one-half again to twice their length, its straight por- 

 tion 10-15 mm. long. 3. A. basiramea. 

 Central awn not coiled at the base. 



Panicle narrow, linear to oblong, the branches short (sometimes long in No. 12), 



erect or ascending. 

 Central awn and sometimes the lateral ones also strongly reflexed, the bend 



semicircular. 4. A, ramosissima. 



Central awn from erect to spreading with no semicircular bend at the base. 

 First scale much shorter than the second, usually about one-half as long. 

 Spikelets crowded, 4-6 on the short branches, which are spikelet- 



bearing to the base or nearly so. 5. A.fasciculata. 



Spikelets not crowded, usually 1-3 on branches naked at the base. 

 Second scale of the spikelet 1.5 cm. or less long, usually 

 equalling or slightly exceeding the flowering scale. 



6. A. Fendleriana. 



Second scale of the spikelet 2 cm. or more long, from one-half 

 again as long as to nearly twice the length of the flowering 

 scale. 7. A. longiseta. 



First scale from a little shorter than to exceeding the second. 

 Spikelets exceeding 2 cm. long ; first scale 5~7-nerved. 



8. A. oligantha. 

 Spikelets less than 1.5 cm. long; first scale i-3-nerved. 



Sheaths glabrous, or pubescent only at the apex. 



Leaves strongly involute, densely villous at the base 



9. A. strict a, 

 Leaves flat, at least not villous at the base. 



First scale generally shorter than or equalling the 



second. 10. A, gracilis. 



First scale usually exceeding the second. 



11. A. purpurascens.' 

 Sheaths, at least the lower ones, densely woolly. 



12. A. lanosa. 

 Panicle diffuse and open, the branches very long and widely spreading. 



13. A. divaricata. 

 Awns articulated to the scale, united at the base into a spiral column. 



Column conspicuous, 6 mm. long or more. 14. A. tuberculosa. 



Column inconspicuous, 2 mm. long or less. 15. A. desmantha. 



1. Aristida dichotoma Michx. POVERTY-GRASS. (I. F. f. 297.) Culms 

 1.5-6 dm. tall, dichotomously branched. Leaves 2.5-7.5 cm. long, less than 2 mm. 

 wide, involute, usually scabrous; spike-like racemes or panicles 5-12.5 cm. long, 

 slender ; spikelets about 6 mm. long ; outer scales nearly equal, usually awn- 

 pointed ; third scale shorter than the second, the middle awn horizontal, the termi- 

 nal straight portion 4-6 mm. long, the lateral awns 2 mm. long or less, erect. Dry 

 sandy soil, Me. to Ont., Neb. and the Ind. Terr., south to Ga. and Tex. Aug.- 

 Sept. 



2. Aristida Curtissii (A. Gray) Nash. CURTISS' ARISTIDA. Culms tufted, 

 2-5 dm. tall, branching Leaves 4-16 cm. long, 1-2 mm. wide; panicle 5-9 cm. 

 long, the branches erect; spikelets generally 10-12 mm. long, rarely longer, the 

 first scale much shorter than the second, which usually about equals the flowering 

 scale; the flowering scale 7-11 mm. long; the lateral awns very short, 1-2 mm. 



