61 



Fig. 39. Aristida oligantha Mx. PRAIRIE TRIPLE-AWN.— a, The outer or 

 empty glumes of a spikelet; b, a floret, showing the three widely-spreading 

 awns' Figs. 85 to 88, in Bui. 7, and 413 to 422, in Bui. 17, illustrate other species 

 of this genus. 



39. ARISTIDA Linn. Sp. PI. 82. 1753. Spikelets 1-flowered on long or short, 

 slender pedicels, in terminal more or less expanded panicles; rachilla articu- 

 lated above the empty glumes and produced into a hard obconical hairy callus 

 below the floral glume, but not extending beyond it Glumes 3; the first two 

 empty, more or less unequal, acute or bristle-pointed, slightly keeled; the 3d or 

 flowering glume firmer in texture than the outer ones, closely rolled around the 

 flower and usually short palea, and terminating in a trifid awn. Grain slender, 

 tightly inclosed by the hardened fruiting glume but free from it. Tufted 

 narrow-leaved grasses, chiefly growing in dry, sandy, or sterile soil. 



Species about 100, in all the warmer regions of the world. Some 40 species are 

 recorded as growing within the United States, chiefly in the southern portions. 



