MANUAL OF THE GRASSES OF THE UNITED STATES 711 



spreading or renexed, flat, broadened at base, the lowermost shorter 

 and relatively slender, some of the upper ones commonly 4 to 5 mm 

 long, usually villous at the base; spikelets usually 2 in each bur. o 

 (Confused with C. tribuloides in early manuals ; C. carolinianus of re- 



Figure 1592.— Cenchrus inccrtus. Bur, two views of spikelet, and floret, X 5. (Curtiss, N.C.) 



cent manuals, not of Walt.)— Sandy open ground, often a weed in 



sandy fields, Maine to Oregon, south to Florida, 

 Texas, and California; Mexican plateau, 

 coastal region of tropical America; southern 

 South America. 



7. Cenchrus tribuloides L. Dune sand- 

 bur. (Fig. 1595.) Resembling C. pauci- 

 florus; culms stouter, soon branching and 



figure i593.-pistribution of radiate-decumbent, rooting at the nodes; 



sheaths usually much overlapping; burs 



(excluding spines) 5 to 6 mm wide and 8 to 9 mm high, usually 



Figure 1594.— Cenchrus pauciflorus. Bur, two views of spikelet, and floret, X 5. (Hitchcock 13582, 



N. Mex.) 



conspicuously villous. © — In loose sands of the coast, Staten 

 Island to Florida and Louisiana; Atlantic coast of tropical America 

 (fig. 1596). 



