356 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



5. Cenchrus gracillimus Nash, Bull. Torrey Club 22: 299. 1895. 



Differs from C. carolinianus in the erect more slender culms, longer narrow 

 blades, and smaller glabrous, less crowded burs. 



Sandy soil, Florida and Jamaica (southern Manchester). Originally de- 

 scribed from central Florida. 



6. Cenchrus microcephalus Nash, sp. nov. 



Culms compressed, slender, 3 to 7 cm. long, ascending from a decumbent 

 base ; blades commonly 12 to 15 cm. long, about 2 mm. wide, sparsely pilose on 

 the upper surface ; burs about 10, scarcely 5 mm. long, erect, smaller than those 

 of any other species of the West Indies, the flattened spines ciliate; spikelets 

 usually 2 in each bur, 4 mm. long. 



Type specimen in the herbarium of the New York Botanical Garden, collected 

 in saline meadows, Berry Island, Bahamas, by Britton & Millspaugh (no. 2249). 

 Known only from the Berry Islands, a second specimen collected on Frozen Cay 

 (Britton & Millspaugh 2211). 



7. Cenchrus echinatus L. Sp. PI. 1050. 1753. 

 Cenchrus brevisetus Fourn. Mex. PI. 2: 50. 1886. 



Culms usually about 50 cm. long, ascending from a decumbent base, branch- 

 ing below ; blades flat, thin, usually elongate, 5 to 10 mm. wide ; spike commonly 

 5 to 7 cm. long. This species is extremely variable in the siae of the burs and 

 length of bristles. Small-burred specimens may be distinguished from C. 

 viridis by the fewer, less-crowded burs and stiffer bristles. 



Open ground and waste places. A common weed throughout the warmer 

 parts of America. Originally described from Jamaica and Curagao. Cenchrus 

 brevisetus was described from Mexico. 



To be found on probably all of the West Indian islands. 



Cexcheus insulaeis Scribn. in Millsp. Field Mus. Bot. 2: 26. 1900. From 

 Mexico to northern South America. Originally described* from Alacran Shoals 

 off the coast of Yucatan. A single immature specimen that may belong to this 

 species comes from Chacachacare Island, Trinidad (Hitchcock 10056). This 

 species differs from C. echinatus in having larger burs with a densely vMlous 

 base. 



8. Cenchrus viridis Spreng. Syst Teg. 1: 301. 1825. 



Cenchrus echinatus var. viridis Spreng. ; Griseb. Fl. Brit. W. Ind. 556. 1864. 



Taller than C. echinatus, more upright, the spikes commonly 10 cm, long. 



Open ground and waste places, Florida to Central America and the West 

 Indies. Originally described from Guadeloupe. To be found on probably all 

 of the West Indian islands. 



51. STENOTAPHRUM Trim 



Spikelets 2 or 3 together in reduced racemes, these embedded in cavities along 

 one side of a broad flat thickened corky articulate axis, the spikeiets falling 

 attached to the joints ; spikelets strongly convex on the inner side ; first glume 

 minute. 



1. Stenotaphrum secundatum (Walt.) Kuntze, Rev. Gen. PI. 2: 794. 1891. 



St. Augustine gsass. 

 Ischaemum secundatum Walt. Fl. Carol. 249. 1788. 

 Rottboellia stolonifera Poir. in Lam. Encycl. 6: 310. 1804. 

 Stenotaphrum amertcaniCm Schrank, Hort. Monac. pi. 98. 1811-1818. - 

 Stenotaphrum sarmentosum Nees, Agrost. Bras. 93. 1829. 



