HITCHCOCK AND CHASE GEASSES OF THE WEST INDIES. 355 



Culms decumbent ; burs pubescent. 



Spines erect or ascending; burs, including spines, less than 5 mm. 



wide 6. C. microcephalus. 



Spines spreading; burs, including spines, commonly 1 cm. or more 

 wide. 

 Burs, excluding spines, 5 to 6 mm. wide, finely pubescent. 



3. C. carolinianus. 

 Burs, excluding spines, 8 to 10 mm. wide, densely woolly. 



4. C. tribuloides. 

 Involucre with a ring of slender bristles at base. 



Burs, excluding bristles, 5 to 7 mm. wide, not densely crowded ; in- 



volucral lobes erect . 7. C. echinatus. 



Burs, excluding bristles, not over 4 mm. wide, numerous, crowded in a 

 long spike ; involucral lobes interlocking 8. C. viridis. 



1. Cenchrus myosuroides H. B. K. Nov. Gen. & Sp. 1: 115. jjI. 35. 1816. 

 PaniGum cenchroides Ell. Bot. S. C. & Ga. 1: 111. 1816. 

 Pennisettim pungens Nutt. Gen. PI. 1 : 54. 1818. 



Cenchrus elliottii Kunth, Rev. Gram. 1: 51. 1829. 



Cenchropsis myosuroides Nash in Small, Fl. Soutkeast. U. S. 109. 1903. 



Glabrous ; culms sparingly branching, woody, often 2 meters tall ; spikes 

 dense, cylindrical, 12 to 20 cm. long, about 8 mm. thick, the erect involucral 

 bristles not exceeding the spikelet. 



3andy soil, Georgia and Florida, Mexico and West Indies to South America. 

 OrigiJially described from BatabanS, Cuba. Panicum cenchroides (on which 

 P. pungens and C. elliottii are based) was described from Georgia. 



Bahamas (Inagua, Turks Island), Cuba (Santiago de Cuba), Haiti, and 

 Porto Rico (Cabo Rojo, Mona Island). 



2. Cenchrus distichophyllus Griseb. Cat. PI. Cub. 234. 1866. 



Culms tufted, wiry, with short internodes, overlapping sheaths, and spreading 

 involute rigid pungent blades, the long-exserted spike about 3 cm. long, the 

 involucre bristles squarrose. 



Sandy pine barrens, westei-n Cuba (Guanes, Wright 3475, the type specimen, 

 Laguna Jovero, Shafer 10717, and San JuliJin, Le6n 6941). 



3. Cenchrus carolinianus Walt. Fl. Carol. 79. 1788. 



Cenchrus echinatus forma longispina Hack. Allg. Bot. Zeitschr. 9: 169. 1903. 



Decumbent, freely branching at the base, the flowering culms ascending; 

 sheaths loose ; blades firm, commonly folded ; spikes short-exserted, of 6 to 12 

 burs. 



Sandy soil, throughout the United States, south to South America. Originally 

 described from South Carolina, the forma longispina from Connecticut. Has 

 been included by many authors under Cenchrus tribuloides. 



Bahamas (Andros, Anguilla Isles, Water Key, New Providence), Cuba, 

 Jamaica, Porto Rico, St. Thomas, Antigua, and Guadeloupe. 



4. Cenchrus tribuloides L. Sp. PI. 10.50. 1753. 



Cenchrus tribuloides var. macrocephalus Doell in Mart. Fl. Bras. 2^: 312. 1877. 



Cenchrus macrocephalus Scribn. U. S. Dept. Agr. Div. Agrost. Bull. 17:110. 

 /. Jf06- 1899. 



Similar to no. 3, rather stockier, the burs larger, woolly. 



Sandy sea beaches. New Jersey to Florida, Bermuda, the Bahamas (New 

 Providence), and Brazil. Originally described from the coast of Virginia. 

 Cenchrus tribuloides var. macrocephalus was described from Brazil. 



