336 Bulletin No. 205 [March, 



tion was correct. Pic describes it as occurring in dry, sandy places in 

 timbered land and openings. It is also mentioned by Flagg ( '78, p. 

 280). This species is distinguished from Stipa spartea by its smaller 

 spikelets in which the glumes are 8 to 10 mm. long and the awn 1.5 

 to 3 inches long. 



Stipa virdula Trin. — This species, commonly called green Stipa, is 

 a native of the western states. In the Field Museum, Chicago, there 

 is a specimen collected by E. Hall, Athens, 1862. Hall brought many 

 seeds of wef^tern grasses back with him and planted them in Athens, 

 and many specimens preserved by him were obtained in this manner. 

 However, most of these seem to have been labeled ' ' raised from seed, ' ' 

 and as no other record has been made of the occurrence of this species 

 in Illinois it seems best to place it on the doubtful list at present. It 

 has a narrow panicle and still smaller spikelets than S. avenacea, the 

 glumes being 6 to 8 mm. long and the awn less than 1.5 inches long. 



20. ARISTIDA L. 



Triple-awned Grass. Needle Grass 



These grasses were found in abundance on the original prairie, and 

 many species are still found in Illinois. They usually grow in large 

 tufts, or bunches, and are readily distinguished by the three-parted 

 awn of the lemma. The glumes are long and narrow and sometimes 

 awn-tipped. The one-flowered spikelets are borne in narrow panicles. 

 Like Stipa, the lemmas have a sharp-pointed callus. The leaves are 

 long and narrow, usually involute. The ligule is very short, never 

 over 2 mm. in length, and is fringed with hairs. The species are of 

 no value for grazing and often are very annoying to grazing animals 

 because of the awns and the sharp-pointed callus which penetrate the 

 skin. There are both annual and perennial species. 



a. Awns jointed to the lemma, and of nearly equal length. 



b. Awns united into a conspienoiis spiral column 6 mm. or more long. 



A. tuberculosa 

 bb. Awns not united into a spiral column, retlexed and somewhat coiled at 

 base. A. desmantha 



aa. Awns not jointed to the lemma. 



b. Central awn nuu-h longer than the lateral awns, the lateral awns erect, 

 c. Central awn forming a distinct spiral at base; second glume not 

 awned. 

 d. Glumes almost equal, awn-pointed, usually 7 to 9 mm. long; 

 lateral awns erect, about 2 mm. long. A. diclwioma 



dd. Glumes unequal, pointed, the first about two-thirds as long as 

 the second, which is 12 to 14 mm. long; lateral awns spread- 

 ing, one-third to one-half the length of the central awn. 



A. basiramea 

 cc. Central awn not forming a distinct spiral, rarely a loose one, the awn 

 either horizontal or reflexed, glumes awned, unequal, the second 

 glume equaling the lemma, 

 d. Central awn always horizontal ; lemma 5 to 7 mm. long. 



A. gracilis 



