30 POACEAE. 



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



Culms finally prostrate and rooting at the nodes, branched; leaf-sheaths 

 loose; blades 1-4 dm. long, 5-16 mm. wide, smooth or rough, flat; spikes 3-12 

 cm. long, finally more or less exserted ; involucres 20-50, containing 4-6 spike- 

 lets, green to purplish, villous at the base, the spines 34 mm. long, the bristles 

 at the base numerous, slender, distinctly barbed for their whole length; spike- 

 lets 67 mm. long. 



Sandy soil, waste places and roadsides. Frozen Cay, New Providence, Eleuth- 

 era, Watling's Island, Fortune Island. Grand Turk and'lnagua: Bermuda; North 

 Carolina to Florida and Texas ; West Indies ; tropical continental America. 

 SOUTHERN BUR-GRASS. 



[Cenchrus hirsutus. Dolley's reference to this name is an error for Cor- 

 chorus hirsiitus into which he was led by Herrick's misprint of Cenchorus hir- 

 sutus for the same species.] 



IS. STENOTAPHRUM Trin. Fund. Agrost. 175. 1820. 



Perennial creeping branched grass, with rather stout flattened culms and 

 short linear leaves. Spikelets spieate or panicled, acute, mostly 2-flowered, 

 imbedded in depressions on one side of the flattened rachis. Scales 4; first 

 scale small or minute, second about as long as the spikelet, third similar to the 

 second, subtending a staminate flower, fourth rigid, enclosing a perfect flower. 

 Stigmas plumose. [Greek, a narrow depression.] A few species of tropical 

 and subtropical distribution, the following typical. 



1. Stenotaphrum secundatum (Walt.) Kuntze, Eev. Gen. 794. 1891. 



Ischaemum secundatum Walt. Fl. Car. 249. 1788. 



Stenotaphrum americanum 'Schrank, PI. Ear. Monac. pi. 98. 1819. 



Widely creeping, sometimes 5 m. long, glabrous, rooting at the lower nodes. 

 Leaf-sheaths keeled, flattened, the blade linear, 3-15 cm. long, 4-10 mm. wide, 

 blunt and rounded at the apex; spikelets about 6 mm. long in spikes 4-13 cm. 

 long. 



Waste places and roadsides, North Bimini, Great Bahama, Ahaco, Andros, New 

 Providence, and Fortune Island : Bermuda : South Carolina to Florida and Texas ; 

 West Indies and tropical continental America. RUNNING CRAB-GRASS. 



19. AEl'STIDA L. Sp. PL 82. 1753. 



Grasses varying greatly in habit and inflorescence. Leaves narrow, often 

 involute-setaceous. Spikelets narrow, 1-flowered. Scales 3, narrow, the two 

 outer carinate; the third rigid and convolute, bearing three awns occasionally 

 united at the base, the lateral awns rarely wanting or reduced to rudiments. 

 Palet 2-nerved. Stamens 3. Styles distinct. Stigmas plumose. Grain free, 

 tightly enclosed in the scale. [Latin, from arista, an awn.] About 100 species, 

 in the warmer regions of both hemispheres. Type species: Aristida adscen- 

 sionis L. 



Awns about equal in length. 



First scale shorter than the second. 



Annual : blades thin, flat or involute. 1. A. adscensionis. 



Perennial : blades thick, folded or involute. 2. A. cognata. 



First scale about as long as the second ; perennial. 3. A. gyrtms. 



Lateral awns minute. 4. A. scabra 



