66 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



7 to 25 cm. long, 2 to 5 mm. (rarely 7 mm.) wide, scabrous on the upper sur- 

 face and sparsely long-pilose, at least toward the base; spikes long-exserted 

 or those of the branches short-exserted, 4 to 10 cm. long, the burs not crowded 

 but on the average closer than in C. gracillimus, the slender axis flexuous. 

 scabrous, sometimes pilose ; burs 3 to 5 mm. wide, excluding the spines, the 

 body finely and densely pubescent, the base glabrous; spines spreading, flat, 

 broadened at base, the lower often obsolete on the outer face of the bur and 

 represented by low knobs or ridges, the upper few, rarely more than 5 mm. 

 long ; body of the bur usually not deeply cleft on the outer face, the lobes com- 

 monly 5 to 7, erect to spreading, 4 to 6 mm. long, rigid and spinelike, long- 

 ciliate at the broad base ; spikelets 1 to 3, 5 to 6 mm. long, about 2 mm. wide ; 

 first glume narrow, pointed, usually present ; second glume about three- 

 fourths the length of the subequal sterile and fertile lemmas ; fruit attenuate, 

 the palea minutely puberulent toward the summit. 



In this species the burs vary greatly in the development of the spines. In 

 Curtis's specimen, from which the figure is drawn, the burs are less spiny 

 than usual. Commonly there are one or two spines on the outer face, besides 

 a ridge or one or two knobs at the base of the body. Occasionally the burs 

 are as spiny as are some in C. pauciflorus, but the plants may be distinguished 

 by their taller culms and erect or ascending habit, and by the glabrous, rela- 

 tively long base of the bur. From C. gracillim/us spiny specimens are dis- 

 tinguished by the pubescent burs. 



DISTRIBUTION. 



Open sandy soil, North Carolina to Florida and west to Texas. 



North Carolina : Wilmington, Hitchcock in 1905. Smithville, Curtis. 



South Carolina : Orangeburg, Amer. Gr. Nat. Herb. 618. 



Georgia : Augusta, Kearney 213. Leslie, Harper 1398. Dooly County, Harper 

 570. Brunswick, Chase 7093; Richer 968. 



Florida : Jacksonville, Curtiss 6019. Duval County, Fredholm 323. St. Augus- 

 tine, Richer 948. Lake City, Chase 4280. East Pass, Tracy 6448. River 

 Junction, Nash 2580. Apalachicola, Bilttnore Herb. 1884. Chipley, Combs 

 610. Palm Beach, Hitchcoch 2283. Miami, Chase 3854. Key Largo, Chase 

 3937. Tampa, Fredholm 6420. Bartow, Combs 1224. Fort Myers, Stand- 

 ley 13040. Punta llassa, Hitchcock 446; Standley 12672. 



Alabama : Springhill, Bush 273. Mobile, Kearney 59. Eufaula, McCarthy in 

 1S88. 



Mississippi : Biloxi, Kearney 210 ; Tracy 3733. Ocean Springs, Tracy in 1889. 

 Chevalier Island, Tracy 4525. Mississippi Sound, Smith in 1885. 



Louisiana: Shreveport, Ball 105. Alexandria, Ball 533. Coushatta, Ball 116. 



Texas : Kerrville, Hitchcock 5258. New Braunfels, Hitchcoch 5236. Austin, 

 Hall 842. San Antonio, Jermy 171 ; Hitchcoch in 1903. Rockport, Chase 

 6017. Corpus Christi, Hitchcoch in 1904. Chillicothe, Ball 974. Without 

 locality, Drummond 347. 



10. Cenchrus microcephalus Nash. 



Cenchrus microcephalus Nash in Hitchc. & Chase, Contr. U. S. Nat. Herb. 18: 

 356. 1917. " Type specimen in the New York Botanical Garden, collected in 

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

 This specimen consists of a single culm about 70 cm. long, single below and re- 

 peatedly branched above. 



