1 16 POACEAE 



3. Aristida baslramea Engelm. Steins tufted, rather slender, 2-6 dm. tall, branch- 

 ing: leaf-blades 3-15 cm. long, 1.5 mm. wide or less, sometimes sparsely pilose above at 

 the base : panicle 3-9 cm. long, the branches erect : spikelets 10-15 mm. long, the first 

 scale much shorter than the second, the flowering scale 7-11 mm. long, considerably shorter 

 than the second, the lateral awns more or less spreading, usually a little spiral at "the base, 

 2-| as long as the central awn which is strongly spiral at the base and with the straight 

 portion 10-18 mm. long. 



In dry fields, Manitoba to Illinois, Nebraska and the Indian Territorj-. Summer and fall. 



4. Aristida Bimpllciflora Chapm. Stems tufted, 4-6 dm. tall, slender, simple or 

 sparingly branched : leaf-blades 3.5-15 cm. long, 1-1.5 mm. wide, flat: panicle 1-2 dm. 

 long, its branches short and appressed : spikelets 8-9 mm. long, crowded, the 2 outer scales 

 1-nerved, about equal or the first a little tlie shorter, tlie flowering scale 5-6 mm. long, the 

 central awn 12-15 mm. long, strongly reflexed, the lateral awns ascending, about 'i as 

 long and much more slender than the central awn. 



In low pine woods, Florida. Fall. 



5. Aristida Mohrii Nash. Stems 5-7 dm. tall, simple : leaf-blades 5-12 cm. long, 

 1-1.5 mm. wide, tliose on the innovations hirsute above : panicles 1.5-3 dm. long, simple : 

 spikelets 10-12 mm. long, on very short pedicels, appressed, scattered, the 2 outer scales 

 1-nerved, the fir,st equalling or often a little exceeding the second, tlie flowering scale 8-9 

 mm. long, the awns of equal thickness, all strongly reflexed, the central one 15-18 mm. 

 long, the lateral ones a little shorter. 



On dry sandy pine ridges, Alabama. Fall. 



6. Aristida ramosissima Engelm. Stems tufted, 2-4 dm. tall, slender, branched: 

 leaf-blades 4-15 cm. long, 1-1.5 mm. wide, flat : panicle 6-10 cm. long, simple, the 

 branches very short and bearing a single usually ascending spikelet : spikelets 1.6-2.2 cm. 

 long, the 2 outer scales usually awned, the first scale 5-7 -nerved, shorter than the 3-nerved 

 second, the flowering scale 15-18 mm. long, the central awn strongly reflexed, 2-3 cm. 

 long, the lateral awns rigid, erect, 1-2 mm. long. 



In dry ground, Illinois and Missouri to the Indian Territory. Late summer and fall. 



7. Aristida fasciculata Torr. Stems tufted, 5-8 dm. tall, branched : leaf-blades 6-12 

 cm. long, 1-2 mm. wide : panicle 7-20 cm. long, its branches short, in fascicles of 2-4, 

 erect or nearly so : spikelets 9-10 mm. long, crowded, the 2 outer scales 1-nerved, the first 

 one h-fi as long as the second, the flowering scale 8-12 mm. long, hispidulous on the keel, 

 the callus densely pilose, the awns ascending, the central one 10-17 mm. long, the lateral 

 awns f-f as long. 



In dry soil, Kansas to California, Texas, Mexico and New Mexico. Fall. 



8. Aristida Fendlerikna Steud. Stems densely tufted, 1.5-2.5 dm. tall, erect, rigid, 

 simple : leaf-sheaths smooth, confined to the base of the stem, a tuft of liairs on each side 

 at the apex ; blades involute, at least when dry, often curved, 0.5 mm. in diameter, those 

 on the stem usually 2, 1.5-5 cm. long, the basal longer : panicle 7-10 cm. long, strict, its 

 brandies short and appressed and usually bearing but a single spikelet, rarely exceeding 

 1.5 cm. long, or sometimes the lower ones with 2 spikelets : spikelets 12-15 mm. long, the 



2 outer scales 1-nerved, the first scale about J as long as the second, the flowering scale 

 9-12 mm. long, equalling or a little shorter than the second scale, the awns ascending, the 

 central one 2-3.5 cm. long, tlie lateral ones a little shorter. 



In dry sandy soil. South Dakota to Utah, Texas and New Mexico. Summer and fall. 



9. Aristida subuniflora Nash. Stems densely tufted, 2.5-3.5 dm. tall, erect, 

 simple : leaf-sheaths usually confined to the base of the stem ; blades involute, at least 

 when dry, usually straight, sometimes curved, those on the stem usually 2, 2-4.5 cm. long, 

 the basal longer : panicle 6-13 cm. long, its branches more or less spreading, the larger 

 ones 2-3 cm. long, bearing 1 or 2 spikelets: spikelets 1.5-2 cm. long, the 2 outer scales 

 1-nerved, the first about I as long as the second, the flowering scale 13-15 mm. long, 

 usually a little shorter than the second scale, the awns ascending, the central one 3-5 cm. 

 long, the lateral awns a little shorter. 



In dry sandy soil, central Texas to New Mexico. Spring and summer. 



10. Aristida "Wrightii Nasli. Stems tufted, 3.5-5 dm. tall, simple, leafy: leaf- 

 blades involute, at least when dry, those on the stem usually 3 or 4, 3-20 cm. long, often 

 curved, as are the commonly longer basal ones: panicle 1-2 dm. long, its branches more 

 or less spreading, the longer usually bearing 2-4 spikelets : spikelets 12-15 mm. long, 

 the 2 outer scales 1-nerved, the first scale about -^ as long as the second, the flowering scale 

 10-12 mm. long, usually a little shorter than the second scale, the awns ascending, the 

 central one 2.5-3 cm. long, the lateral awns a little shorter. 



In dry sandy soil, Kansas to Texas and New Mexico. Summer and fall. 



