HITCHCOCK AND CHASE — NORTH AMERICAN GRASSES. 



75 



the hairs longer and denser at the summit; ligule ciliate, 2 to 2.5 mm. long; 

 blades mostly flat, rather firm, ascending or spreading, 3 to 18 cm. long, 3 to 7 

 mm. wide, tapering from the base to an attenuate apes, very scabrous on both 

 surfaces ; spikes reduced to 1 to 4 burs, commonly 1 or 2, the terminal spikes 

 mostly long-exserted, those of the branches overtopped by the subtending leaf ; 



Fig. 20. — Cenchrus palmeri. From the type specimen. 



burs (including the spines) 2 to 2.5 cm. high and 2.5 to 4 cm. broad, the body 

 scarcely oblique, depressed-globose, truncate at base, about 10 mm. high and 12 

 mm. wide, pale tawny-canescent ; spines numerous, spreading or reflexed, usually 

 blackish purple above the villous-canescent, greatly thickened base, but some- 

 times yellow, the lowermost short, stout and thornlike, the others long-attenuate, 

 retrorsely barbed and sometimes flexuous at the needle-like tips, commonly some 



