48 GRAMINEAE (GRASS FAMILY) 



2. Aristida longiseta Steud. Syn. PI. Gram. 420. 1855. Densely tufted 

 glabrous perennial, 1-4 dm. high, with numerous involute basal leaves, and 

 erect simple culms: panicles few-flowered, 1-2 dm. long, its branches solitary 

 or 2 or 3 at the lower nodes, each bearing 1-3 spikelets (usually 1): spikelets 

 20-25 mm. long; empty glumes unequal, acute or with a mucronate tip 1 mm. 

 long; the first shorter than the lemmas and about one half the length of the 

 second; the second much exceeding the lemma; setae nearly equal, about 

 7 cm. long. Sandy soil; throughout our range. 



2a. Aristida longiseta robusta Merrill, U. S. Dept. Agr. Div. Agros. Cir. 

 34. 5. 1901. Stout, 3-4 dm. high, with more rigid inflorescence and usually 

 longer leaves than in the species: glumes prominently cleft at apex, bearing in 

 the cleft a scabrous awn about 2 mm. long. Same range. 



26. Aristida longiseta Fendleriana (Steud.) Merrill, 1. c. Two to four dm. 

 high: basal leaves numerous: panicle strict: glumes generally cleft at the 

 apex and bearing a short awn; second glume equaling or slightly exceeding 

 the lemma; setae subequal, 2-3 cm. long. Eastern Wyoming, Colorado, and 

 southward. 



17. STIPA L. FEATHER GRASS 



Tufted perennials, the leaves usually convolute, rarely flat, the inflorescence 

 paniculate. Spikelet 1-flowered, narrow. Glumes narrow, acute or acuminate, 

 obtuse or awned; lemma rigid, convolute, with a hairy callus at base, and 

 bearing a more or less bent awn, which is spiral at the base and articulated 

 to the glume; palet 2-nerved. Stamens 3, rarely fewer. Styles short, dis- 

 tinct; stigmas plumose. Grain narrow, free, tightly inclosed in the lemma. 



Awn less than 5 cm. long. 

 Panicle loose. 



Awn scabrous . . . . . . . . 1. S. Richardsonii. 



Awn plumose . . . . . . . . 2. S. mongolica. 



Panicle contracted and spike-like. 



Awn plumose, the hairs over 1 mm. long. 



Glumes 16-18 mm. long . ..'.'.. . . . . 3. S. speciosa. 



Glumes 10-12 mm. long . . . . . . 6. S occidentalis. 



Awn not plumose, pubescence, if any, less than 1 mm. long. 

 Lemma with a distinct crown of hairs at apex. 



Glumes 10-14 mm. long . . . . . 4. S. Scribneri. 



Glumes 7-10 mm. long 5. S. Lettermanii. 



Lemma not crowned with a tuft of hairs or the crown, if any, 

 indistinct. 



/" Sheaths pubescent 8. S. Williamsii. 



Sheaths smooth. 



Very tall, 8-18 dm. high 10, S. Vaseyi. 



Less than 10 dm. or rarely 12 dm. high. 



Awn 35-40 mm. long . . . . . 9. S. Nelsonii. 



Awn less than 35 mm. long. 



Margins of sheaths pilose . . . . .11. S. viridula. 

 Margins of sheaths not pilose . . . 7. S. columbiana. 



Awn 5 cm. or more in length. 



Awn plumose 12. S. neo-mexicana. 



Awn not plumose. 



Glumes 24-36 mm. long 13. S. spartea. 



Glumes 18-24 mm. long 14. S. comata. 



1. Stipa Richardsonii Link, Hort. Berol. 2: 245. 1833. Erect, slender, 

 6-9 dm. high: leaves long and narrow, involute: panicle loose and open, more 

 or less nodding, 7-12 cm. long, with very slender, few-flowered branches: 

 spikelets 8-9 mm. long, broadly lanceolate, acute; glumes unequal, the lower 

 about 9 mm. long, the upper one fourth shorter, both 3-nerved; lemma 6 mm. 

 long, sparsely hairy, brown; awn slender, scabrous, 12-20 mm. long. Through- 

 out our range and northward. 



2. Stipa mongolica Turcz. in Trin. Gram. Suppl. 42. 1836. Slender, 

 densely tufted, about 3 dm. high, with short, setaceous leaves and loosely 

 few-flowered purplish panicles 7-10 cm. long: glumes 5 mm. long, equal, ob- 

 tuse, smooth, subhyaline; lemma about 4 mm. long, thinly hairy below and at 

 the 2- toothed apex; callus short, obtuse; awn 12-16 mm. long, geniculate and 

 twisted below, long-plumose-hairy. Mountains of Colorado. 



