14 WEED FLORA OP IOWA 



Distribution. — Old witch grass is common throughout the state, 

 frequently as a weed. It is variable, the form occurring in cul- 

 tivated fields being stout and hispid; but when occurring in moist 

 meadows and old lake beds it has slender and somewhat capillary 

 branches. In Iowa it is quite common in Plymouth, Woodbury, 

 Muscatine, Story, Emmet, Franklin, Clinton, Carroll, Crawford, 

 Pottawattamie, Scott and other counties. 



Extermination. — This annual grass is easily exterminated by cul- 

 tivation. It seldom gives trouble in well cultivated com fields. It 

 might be well also, when the weed is abundant, to rotate with some 

 leguminous crop. 



Sprouting Crab Grass {Panicum dichotomiflorum Mx.). 



Description. — ^A' smooth, usually much-branched annual with 

 stems 2-4 or 6 ft. tall, rather coarsely spreading or ascending 

 (rarely erect) ; long, flat leaves and diffuse terminal and lateral 

 panicles; sheaths smooth, lax, somewhat flattened; ligule ciliate; 

 leaf-blade 6-12 or 24 in. long, 2-10 lines wide, acute, scabrous on 

 the margins and sometimes also on the prominent nerves, rarely 

 pilose on the upper surface; panicles pyramidal, 4 or 5-12 or 15 

 in. long, the primary and secondary branches spreading, scabrous; 

 spikelets rather crowded upon short, oppressed and scabrous pedi- 

 cels, lanceolate-ovate; acute 1-1% lines long, smooth, green or 

 purplish ; lowest glume embracing the base of the spikelet, usually 

 obtuse and nerveless, rarely 1-3-nerved, %-% as long as the 

 nearly acute 5-7-nerved second and third glumes, the latter having 

 sometimes a hyaline palea in its axil; floral glume elliptical, sub- 

 acute, smooth and shining, a little shorter than the larger outer 

 glumes ; anthers saffron yellow. 



Distribution. — Widely distributed in eastern North America, 

 common in m^any parts of Iowa, as Ames, Des Moines, Sioux City, 

 Council Bluffs, Davenport, Eddyville. 



Extermination. — Prevent the formation of seed and give thor- 

 ough cultivation. 



