HITCHCOCK AND CHASE — NORTH AMERICAN GRASSES. 



63 



This apparently rare species differs from C. echinatus in the larger burs, 

 more numerous and longer bristles, the more uniformly cleft body with more 

 slender-pointed lobes, and the conspicuously ciliate bases of the inner broad- 

 based bristles and involucre lobes, these minutely pubescent on the back. Some 

 specimens of C. echinatus, with burs having exceptionally long and numerous 

 bristles, resemble C. insularis. 



■ V v / ' I ! 



/i, MiAiMii 





Ml /I 



(M mm 



Fig. 13. — Cenchrus insularis: From the type specimen. 

 DISTRIBUTION. 



Sandy beaches, Alacran Shoals, off the northern coast of Yucatan, northern 

 Colombia, and in Brazil. 



Yucatan : Pajaros Island, Alacran Shoals, MillspaugJi 1759. 

 Colombia : Santa Marta, Smith 159. Puerto Colombia, Hitchcock 9938. 

 Brazil : Lagoa Santa, Warming in 1863, 



8. Cenchrus gracillimus Nash. 



Cenchrus gracillimus Nash, Bull. Torrey Club 22 : 299. 1895. " Florida, oc- 

 curring in the high pine land. . . . My nos. 188 and 288, collection of 1894." 

 Nash's nos. 188 and 288 of 1894 were " collected in the vicinity of Eustis, Lake 

 County." His no. 188 in the herbarium of the New York Botanical Garden is 

 taken as the type. 



DESCRIPTION. 



Plants perennial, at length forming dense clumps, glabrous as a whole ; culms 

 20 to 80 cm. tall, commonly branching from the lower nodes, but sometimes 

 remaining simple, often scabrous toward the summit, compressed, slender, 

 wiry, erect or ascending, the outer culms of large clumps geniculate at base ; 

 sheaths loose, keeled, the lower overlapping, sometimes sparsely pilose ; ligule 

 ciliate, about 0.5 mm. long; blades usually folded and stiffly flexuous, 5 to 20 

 cm. long, 2 to 5 mm. (usually 2 to 3 mm.) wide, scabrous on the upper surface 

 and sometimes pilose at the base ; spikes usually long-exserted, 2 to 6 cm. 

 long, the burs not crowded, sometimes distant more than their own length, the 



