GRASSES OF IOWA. 55 



North America. Common. Dry, sandy soil. Massachusetts to New 

 Jersey, south to Florida (Simpson); west to Texas (College Station, 

 Pammel), North Carolina (Vasey), Mexico (Palmer, 502), Missouri 

 (St. Louis, Eggert; Jefferson, Eggert) ; Nebraska, Iowa and Michigan. 



5. PANICUM GLABRUM. 



Panicum glabrum Gaudin. Agrost. 1: 22. 1811. Watson and Coul- 

 ter. Gray Man. Bot. 630. 1890. (6 ed.) Scribner. Grasses of Tenn. Bull. 

 Univ. Tenn. Agr. Exp. Sta. 7: 39. /. 27. 1894. Scribner and Merrill Rho- 

 dora. 3: 1002. Vasey Contr. U. S. Nat. Herb. 3: 24. 



Panicum lineare Krock. F. Sil. 1: 95. 1787. Beal. Grasses of N. 

 Am. 2: 110. 1896. 



Panicum humifnsntn (Pers.) Kunth. Rev. Gram. 1: 33. 1835. Scrib- 

 ner. Am. Grasses. Bull. U. S. Dept. Agr. Div. Agros. 7: 43. /. 37. 

 1900. (3 ed.) 



Syntherisma linearis Nash Bull. Torr. Bot. Club. 22: 420. 1895. 



Syntherisma linearis (Krock) Nash in Britton and Brown. 111. Fl. 1: 

 111. /. 241. 1896. 



Syntherisma serotina Walt. Fl. Car. 76. 1788. 



Syntherismi glabra. Schrad. Fl. Germ. 1: 163. 1806. 



Paspalum ambiguum D . C. Fl. Gall. 123. 1806. 



Digitaria humitusa Pers. Syn. 1: 85. 1805. 



DESCRIPTION. 



Smooth Crab Grass. An annual 6 inches to 2 feet (1^-6 dm.) 

 high, closely resembling P. sanguinale in habit, but smooth throughout, 

 'excepting a few hairs at the throat of the sheaths. Spikelets two to 

 seven, the spikelets are smaller, about 1 line (2 mm.) in length. First 

 glume very minute or obsolete; second and third glumes'nearly equal 

 in length, or the second a little shorter than the fourth, pubescent of the 

 back. 



Smooth crab grass is common in eastern and central Iowa, especially 

 in the flood plains of streams. It is also becoming common in lawns 

 where it is a most troublesome weed. 



DISTRIBUTION. 



Iowa. Steamboat Rock, 3173 (Miss King) ; 37,724, Manchester 

 (Hall); Greenfield (Stewart); Grand Junction (Thompson); Ames 

 (Hitchcock, Beardslee) ; 2220 Ft. Dodge, 2252 Wilton Junction, 

 Hawarden, Fagle Grove Sioux City Ledges, Boone County, 109 Da- 

 kota City, Clinton, Carnarvon, Turin, Carroll, 984 Des Moines. 

 Marshalltown, Fagle Grove (Pammel) ; 783, Armstrong (Pammel and 

 Cratty) ; Iowa City (Hitchcock); Keystone (Koch); 168, Ledges 

 (Pammel and Ball); Fayette (Fink); Hampton ( Hirshman) ; In- 



