354 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Setaria antillarum Kunth, R6v. Gram. 1: 46. 1829. 



This little-known species is distinguished by the slender spikes with spikelets 

 about 2 mm. long, solitary in the involucre, the bristles naked, one being 

 2 or 3 times as long as the spikelet, the others about as long as the spikelet. 

 The type specimen in the Florence Herbarium is said to have come from the 

 "Antilles." We have seen no other specimens. 



3. Pennisetum setosum (Swartz) Rich.; Pers. Syn. PI. 1: 72. 1805. 

 Cenchrus setosus Swartz, Prodr. Veg. Ind. Occ. 26. 1788. 

 Pennisetum alopecuroides Desv. ; Hamilt. Prodr. PI. Ind. Occ. 11. 1825. 

 Pennisetum erubeseens Desv. ; Hamilt. Prodr. PI. Ind. Occ. 11. 1825. 

 Pennisetum hamiltonii Steud. Syn. PL Glum. 1: 108. 1854. 



A tall leafy branching perennial, erect or ascending from a geniculate base, 

 the long flat blades pubescent or scabrous, the purplish^ spikes 10 to 15 cm. 

 long, the long slender bristles at maturity spreading horizontally or slightly 

 reflexed. 



Grassy slopes and open woods, Mexico and West Indies to South America; 

 also in tropical Asia and Africa. Originally described from the West Indies, 

 the exact locality not indicated. Pennisetum alopecuroides was described from 

 the West Indies, P. erubeseens from St. Thomas. Pennisetum hamiltonii was 

 based on P. alopecuroides. 



Cuba (San Juan de Buenavista), St. Eustacius, Guadeloupe, Dominica, Mar- 

 tinique, St. Vincent, Grenada, Barbados, Trinidad, and Tobago. 



4. Pennisetum orientale triflorum (Nees) Stapf ; Hook. f. Fl. Brit. Ind. 7: 86. 



1896. 



Pennisetum triflorum Nees ; Steud. Syn. PI. Glum. 1 : 107. 1854. 



Culms ascending from a hard knotted crown with numerous short leafy 

 shoots; spikes commonly 20 cm. long, the spreading turbinate involucres very 

 feathery. 



Naturalized around Cinchona, Jamaica, and escaped from cultivation on the 

 grounds of the experiment station in Trinidad; native of India. Originally 

 described from Nepal. 



5. Pennisetum ciliare (L.) Link, Hort. Berol. 1: 213. 1823. < 

 Cenchrus cilaris L. Mant. PI. 302. 1771. 



Pennisetum cenchroides Rich, in Pers. Syn. PI. 1 : 72. 1805. 

 A low, spreading perennial, with short spikes of readily deciduous involucres. 

 Originally described from Africa. Introduced in Porto Rico (La Vigia, Ponce). 



50. CENCHRUS L. 



Sand bur. 



Spikelets 1 to 4 together, subtended and surrounded by a spiny bur formed 

 of adnate sterile branches, the burs subsessile along a common axis, falling 

 with the spikelets and permanently inclosing them; spikelets acuminate, the 

 first glume sometimes obsolete. 



Called also " burgrass," and, in Cuba, " guizazo." 



Plants perennial. 



Bristles of bur separate nearly to the base ; blades 20 cm. or more long. 



1. C. myosuroides. 



Bristles united at base ; blades 2 to 3 cm. long 2. C. distichophyllus. 



Plants annual. 



Involucre with flattened spines, no ring of slender bristles at base. 



Culms erect ; burs glabrous __. 5. C. gracillimus. 



