72 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Costa Rica : Puntarenas, Hitchcock 8540. 



Panama : Point Chame, Hitchcock 8164. 



Cuba: Habana, Leon 1881, 836, 2391, 3445, 3453; Palmer & Riley 1146. Tris- 

 cornia, Hitchcock 492. Playa de Cojimar, Hitchcock 493. Without lo- 

 cality, Wright 3476. 



Jamaica: Black River, Hitchcock 9637. 



Pokto Rico : Santurce, Chase 6345^. 



Virgin Islands : St. Thomas, Raunkiaer 634. 



Leeward Islands : Antigua, Wullschlacgel 634. 



Brazil: Rio Janeiro, Wilkes Expl. Expect.; Warming in 1863. 



Uruguay: Costa Platense, Arechavaleta. 



Argentina : Cordoba, Stuckert in Kneucker Gram. Exs. 427. Without locality, 

 Lorent~ 697; Jorgensen 1147. 



12. Cenchrus tribuloides L. 



Cenchrus tribuloides L. Sp. PI. 1050. 1753. " Habitat in Virginiae maritimis." 

 The type specimen in the Linnaean Herbarium, 1 marked " K," indicating that it 

 \v;'.s collected by Kalm, consists of two branching plants. 



Cenchrus echinatus tribuloides Torr. Fl. North. & Mid. U. S. 1: 69. 1823. 

 Based on C. tribuloides L. 



Cenchrus vaginatus Steud. Syn. PI. Glum. 1 : 110. 1854. " Culta in horto 

 Paris : sub. Cenchrus tribuloides macrocarpus." This specimen has not been ex- 

 amined, but the detailed description applies remarkably well to the true C. 

 tribuloides. 



Cenchrus tribuloides macrocarpus Steud. Syn. PI. Glum. 1: 110. 1854. A 

 garden name given as synonym of C. vaginatus Steud. 



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

 1877. Described from a specimen in Martius's herbarium, " e Brasilia oriunda." 

 The type has not been examined, but the brief description can refer to nothing 

 else known to us. The involucre, described as less villous than that of C. 

 tribuloides, would indicate an exceptional specimen, such as Chase's no. 4531 

 from South Carolina and several of the West Indian specimens. 



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

 J/06. 1899. Based on C. tribuloides var. macrocephalus Doell. 



DESCRIPTION. 



Plants annual, very leafy ; culms stout, at first erect, soon branching and 

 becoming radiate-decumbent, 15 to 60 cm. long, the ends ascending, rooting at 

 the nodes and with numerous ascending branches 10 to 30 cm. tall, scabrous or 

 pilose at the summit ; sheaths usually much overlapping, sharply keeled, broad, 

 those below the spikes inflated, pubescent at least along the margin and with a 

 dense tuft of hairs on each side at the summit ; ligule ciliate, 1 mm. long ; 

 blades flat or folded, the margins usually more or less involute, firm, spreading, 

 3 to 18 cm. long (seldom over 12 cm. long), 4 to 7 mm. wide, tapering from 

 base to apex, scabrous on the upper surface; spikes numerous, usually ex- 

 ceeded by the subtending leaf, 3 to 9 cm. long, the burs crowded, the axis flexu- 

 ous, scabrous or pilose ; burs more oblique than in any other of our species, 5 

 to 6 mm. wide and 8 to 9 mm. high (excluding the spines), usually conspicu- 

 ously villous, but sometimes short-pubescent only, the base puberulent, usually 

 with a few long hairs at the very base ; spines finally spreading, fiat, the lower- 

 most relatively short and slender, the upper ones broadened at the base, some- 



1 See p. 45. 



