FLOWERING PLANTS AND FERNS OF ARIZONA 149 



5. Setaria villosissima (Scribn. and Merr.) Schum., Just's Bot. 



Jahresber. 28 *: 417. 1902. 



Chaetochloa villosissima Scribn. and Merr., U. S. Dept. Agr., 

 Div. Agrost. Bui. 21: 34. 1900. 



Arizona without definite locality (Emersley 19 and 21 C, in 1890). 

 Texas and Arizona. 



6. Setaria macrostachya H. B. K., Nov. Gen. et Sp. 1: 110. 1815. 

 Coconino, Yavapai, Greenlee, Cochise, Santa Cruz, and Pima 



Counties, 2,000 to 7.000 feet, dry, rocky soil. May to October. Texas 

 to Colorado. Arizona, and Mexico. 



This species is referred to Chaetochloa composite in YVoot. and 

 Standi., Flora New Mexico. 



7. Setaria scheelei (Steud.) Hitchc, Biol. Soc. Wash. Proc. 41: 163. 



1928. 



Panicum scheelei Steud., Syn. PL Glum. 1: 51. IS 54. 



Near base of the Baboquivari Mountains. Pima County (Harrison 

 and Kearney 8018). Texas and Arizona. 



71. CENCHRUS. Saxdbur 



Decumbent or geniculate spreading annuals, with flat leaf blades 

 and rather dense spikelike racemes of burs; burs composed of numer- 

 ous coalescing bristles, enclosing 2 to 4 spikelets, falling entire; first 

 glume usually half to two-thirds as long as the spikelet ; second glume 

 and sterile lemma equal, subacute or acuminate; fruit acuminate, 

 about as long as the second glume and the sterile lemma. 



The plants make good forage when young, but become trouble- 

 some after maturity. The burs are especially obnoxious when mixed 

 with hay, their barbed spines being painful to human beings and 

 animals, difficult to extract, and sometimes causing inflammation 

 and infection. 



Key to the species 

 1. Burs with a ring of slender bristles at base; spikelets usually 4 in each bur. 



1. C. ECHIXATFs. 



1. Burs with no ring of slender bristles at base; spikelets usually 2 in each bur. 



2. C. PAUCIFLORUS. 



1. Cenchrus echinatus L., Sp. PL 1050. 1753. 



Maricopa and Yuma Counties, a troublesome weed in irrigated 

 land and cultivated fields. Open ground and waste places. South 

 Carolina to Florida and Arizona; tropical America. 



2. Cenchrus pauciflorus Benth., Bot. Voy. Sulph. o<o. 1S40. 

 Navajo, Yavapai, Greenlee. Maricopa. Santa Cruz, and Pima 



Counties, up to 5.500 feet, open sandy ground, July to September. 

 Maine to Oregon, south to Mexico; coastal regions of tropical America 

 and southern South America. 



72. IMPERATA. Satixtail 



Slender erect perennials from hard scaly rhizomes, with linear leaf 

 blades narrowed toward base to the thickened midrib, ami narrow 

 terminal silky panicles; spikelets all alike, paired, awnless, unequally 



