732 



MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



Figure 1117. — Cenehrus echinatus. Bur, two views of spikelet, and floret, X 5. (Hitchcock 9397, Jamaica.) 



usually geniculate, branching at base, 

 25 to 60 cm. long; blades 3 to 8 mm. 

 wide, pilose on the upper surface near 

 the base; raceme 3 to 10 cm. long, the 

 burs larger, fewer, and less crowded 

 than in C. brownii; bur 4 to 7 mm. 

 high, as broad or broader, pubescent, 

 the lobes of the involucre erect or 



forming dense clumps, glabrous as a 

 whole; culms slender, wiry, erect or 

 ascending, 20 to 80 cm. tall; blades 

 usually folded, 2 to 3 mm. wide; ra- 

 ceme 2 to 6 cm. long, the burs rela- 

 tively distant, about 3.5, rarely as 

 much as 5 mm., wide (excluding 

 spines), tapering at base, glabrous; 



Figure 1118. — Cenehrus gracillimus. Bur, two views of spikelet, and floret, X 5. (Type coll.) 



bent inward but not interlocking; 

 spikelets usually 4 in each bur. O 

 — Open ground and waste places, 

 South Carolina to southern Califor- 

 nia; a common weed in tropical Amer- 

 ica; sparingly introduced in Hawaii 

 and Malaysia. 



4. Cenehrus gracillimus Nash. 

 (Fig. 1118.) Perennial, at length 



spines spreading or reflexed, flat, 4 to 

 6 mm. long, the lobes about 8; spike- 

 lets 2 or 3 in each bur. 21 — Sandy 

 open ground and high pineland, Flor- 

 ida, southern Alabama and Missis- 

 sippi; Cuba, Jamaica. 



5. Cenehrus incertus M. A. Curtis. 

 Coast sandbur. (Fig. 1119.) Peren- 

 nial, glabrous as a whole; culms 25 to 



