GRASSES OF IOWA. 



121 



6. ARISTIDA INTERMEDIA. 



Aristida intermedia. Scrib. and Ball. Bull. U. S. Dept. Agrl. Div. 

 Agros. 24: 44. 



DESCRIPTION. 



Intermediate Aristida. A slender, somewhat geniculate, branch- 

 ing annual, i to 2 J, feet (3-7 dm.) high, with involute leaves and long 

 slender, panicles. Culms smooth, freely branching, purplish, the outer 

 branches geniculate, ascending; sheaths usually shorter than the inter- 

 nodes, smooth or the 

 lower sparsely hirsute, 

 especially on the margins, 

 and purplish ; ligule a 

 very short ring, .2 lines 

 (0.4 mm.) long or less, 

 fringed with short hairs; 

 blades \% to 5 inches (5- 

 15 cm.) long, 1 line (2 

 mm.) wide, erect, rigid, 

 involute, sometimes 

 sparsely hirsute near the 

 base. Panicle, 5 to \\ 

 feet (2-4 dm.) long, slen- 

 der, often rlexuose; 

 branches short, § to 1^ 

 inches (2-4 cm.) long, 

 appressed. Spilcelets, 4. to 

 5 lines (8-10 mm.) long; 

 empty glumes narrowly 

 lanceolate, attenuate into 

 a rather long awn, nearly 

 equal or the upper 

 longer, 3^ to 4^ lines ( 7- 

 9 mm.) long, 1 -nerved, 

 scabrous^purplish ; flower- 

 ing glume 3i to \\ lines 

 (7-9 mm.) long, strongly 

 scabrous above the mid- 

 dle, equalling or exceed- 

 ing the empty glumes, 

 sometimes regularly spotted as in A. gracilis; awns all spreading, the 

 middle one 9 to 1 1 lines (18-22 mm.) long, the lateral ones 7 to8 lines 

 (14-17 mm.) long, all variable. This species is most closely allied to 

 A.. gracilis ,but differs in its larger sizt.and especially in the much longer 

 florets and awns. It is neatly intermediate between A. gracilis and A. 

 purpurascens, with the habit of the former and spikelets more like those 

 of the latter. 



Fig. 87. 



Aristida intermedia— a, spikelet. (Div. 

 Agros. U. S. Dept. Agrl.) 



