aristida GRAMINE^E 739 



PHLEUM 



clothed with long white hairs \V 2 lines lone, terminating in an awn 2 lines 

 long which falls at maturity : palet conical, smooth, hard, brown. On 

 sandy plains. Eastern Oregon to California, Texas and Brit. Columbia. 



0. exigua Thurber Bot. Wilkes 481. Stems slender, erect, 6-15 inch- 

 es high, hispid, the nodes black, scarcely constricted: leaves of sterile 

 shoots numerous with close striate hispid sheaths and narrow involute 

 wiry scabrous blades 4-7 inches long, of the stem usually 4, lower 2 with 

 short overlapping sheaths and blades like the radical ones, next sheath 

 above much shorter than the internodes with blades 2-4 inches long : 

 liguies acute, 1-2 lines long: panicle narrow, secund, 2-3 inches long, its 

 branches usually in pairs, erect: unequal: empty glumes oblong-ovate, 

 barely acute, or abruptly acuminate, membranous, minutely scabrous, 

 equal, 2-2^ lines long flowering glumes herbaceous, becomiug chartaceous, 

 obtuse or with purple teeth at the apex, short-pubescent throughout, 5 

 nerved, the nerves united above : awn persistent, minutely hispid, 2-3 lines 

 long: palet equalling the glume, obtuse or bidentate at the apex. In the 

 mountains of Oregon and Washington. 



0. Hendersoni Vasey Contrib. U. S. Nat. Herb. 7, 267. Stems 

 densely tufted, 7-10 inches high: lower sheaths rather loose: leaves scab- 

 rous, conduplicate, rigid pungent 4-5 inches long: panicle narrow 2^-4 

 inches long, its branches mostly in twos, the longest \%-2% inches long 

 bearing 2-4 spikelets near the ends : empty glumes broadly oblong, obtuse 

 and toothed, the first 3-nerved, the second 5-nerved : flowering glume linear, 

 oblong, 2 lines long, smooth, coriaceous, obscurely 5-nerved, bearing 2 lateral 

 teeth : awn curved, caducous, 5-6 lines long. Washington. 



23 ARISTIDA L. Sp. 82. 



Annual or perennial grasses with narrow leaves and various 

 inflorescence. Spikelets narrow, one-flowered. Glumes 3, narrow, 

 the 2 outer empty, carinate, the third rigid and convolute, bearing 3 

 d,wns, sometimes united at base, the lateral ones rarely wanting 

 or reduced to rudiments. Palet 2-nerved. Stamens 3. Styles 

 distinct. Stigmas plumose. Grain free, tightly enclosed in the 

 glume. 



A. purpurea Nutt. Trans. Am. Phil. Soc. (II) v, 145. Stems slen- 

 der, tufted, erect, nearly smooth, 1-2 feet high : lower leaves with narrow 

 close sheaths and slender involute blades 4-10 inches long: lower sheaths 

 longer than the internodes, the upper ones much shorter: liguies a line 

 of fine short hairs : panicle rather loose, narrow, 4-6 inches long, its bran- 

 ches 2-3 at each node, unequal the lower 1-2 inches long, naked below : 

 spikelets 5-6 lines long, first glume narrowly lanceolate-linear, emargin- 

 ate, mucronate, hispid on the keel, 1-nerved, 4-5 lines long; the second 

 similar but nearly 2 lines longer, stipe hairy : flowering glume linear-lan- 

 ceolate, recurved, slightly hispid on the nerves above, 4 lines long, termina- 

 ing in 3 separate slender awns 1-2 inches long: palet obovate, thin, about 

 % line long. On prairies and ridges, eastern Washington to Brit. Colum- 

 bia, Idaho and Texas. 



A. oligantha Michx. Fl i, 41. Glabrous annual : stems slender, 1-2 

 feet high, erect, dichotomously branched, smooth or roughish : sheaths 

 loose, longer than the internodes : liguies very short, minutely ciliate: 

 leaves 1-6 inches long, %-\ line wide, smooth, the larger ones "attenuate 

 into a long slender point : spikelets few, borne in a lax spike-like panicle: 

 first glume 5-nerved, an inch long, attenuate or short-awned equalling or 

 shorter than the second which bears an awn 2-4 lines long : flowering 

 glume shorter than the first one, bearing 3 slender divergent or spreading 

 awns, the middle one 1-3 inches lone, the lateral ones somewhat shorter. 



