20 POACEAE. 



rough: panicle usually interrupted below, 1-3.5 dm. long, 2-5 cm. in diameter; 

 bristles 1-3, green, 8-11 mm. long: spikeleta elliptic, acute, 2 mm. long. 

 Everglades. F. K. 



3. C. macrospenna Scribn. & Merr. Stems 6-12 dm. tall: leaf -blades linear- 

 lanceolate, 1-3 dm. long: panicle 1-2.5 dm. long, 2-4 cm. in diameter, exclusive 

 of the bristles: bristles single, 1.5-3 cm. long, green: spikelets narrowly ovoid, 

 acute, 3 mm. long, the flowering scale acute, narrowly ovoid, finely transverse- 

 rugose. Hammocks. F. K. (Bah.) 



4. O. corrugat* (Ell.) Scribn. Stems 3-10 dm. tall: leaf -blades narrowly 

 linear, 1-3 dm. long: panicle 0.5-1.5 dm. long, 415 mm. in diameter exclusive 

 of the bristles: bristles solitary or rarely 2 at each spikelet, 5-15 mm. long: 

 spikelets ovoid, acute, about 2 mm. long, the fourth scale very strongly trans- 

 versely and coarsely undulate-rugose. Hammocks and low pinelands. 



20. CENCHEOPSIS Nash. Erect plants with long rootstocks and terminal 

 spicate inflorescence. Spikelets single, the involucre of 1 or 2 outer rows of 

 barbed bristles and 1 or 2 inner rows of barbed spines which are 2-4 times as 

 long as the bristles and about equalling the spikelet. Scales 4. 



1. O. myosuroides (H.B.K.) Nash. Stems 6-14 dm. tall: leaf -blades 1-3 dm. 

 long, 3-8 mm. wide: spikes 5-20 cm. long: involucres numerous: spikelets 

 about 5 mm. long. Pinelandu. F. K. (Bah., Cvba, Ant.) 



21. CENCHRUS L. Diffuse plants with terminal spikes. Spikelets 2-6, 

 in an involucre of two thick hard valves. Scales 4, awnless. SAND-BUR. 

 SAND-SPUR. BUR-GRASS. COCKSPUR. 



Involucre pubescent 1. O. carolinianug. 



Involucre glabrous. 2. C. gracUHmut. 



1. C. carolinlanus L. Stems 2-6 dm. long, branching: leaf -blades 6-12 cm. 

 long, 4-8 mm. wide: spikes 3-6 cm. long: involucres 6-20, the spines 3-4 mm. 

 long: spikelets 6-7 mm. long, usually not exserted beyond the involucre. 

 Hammock*. F. K. (Ber., Bah., Cvba, Ant.) 



2. 0. gracUlimus Nash. Stems 3-6 dm. tall, slender: leaf -blades 5-8 cm. long, 

 about 2 mm. wide, acuminate: spikes usually long-exserted, 3-5 cm. long, bear- 

 ing 3-6 distant purplish involucres with a deeply furrowed and glabrous base, 

 the spines purple, 5-6 mm. long: spikelets about 8 mm. long, exserted beyond 

 the involucre one-third to one-half their length. Pinelands. 



22. 8TENOTAPHBUM Trin. Creeping, much-branched plants, with ter- 

 minal spikes or spike-like panicles. Spikelets 2- (rarely 1-) flowered, in 2's-4's 

 in short spikes. Scales 4. 



1. 8. secundatmn (Walt.) Kuntre. Stems compressed: leaf -blades rounded at 

 the apex, usually less than 1 dm. long, 4-10 mm. wide: spikelets 3.5-5 mm. 

 long. Coastal sand-dunes. F. K. (Ber., Bah., Cuba, Ant.) SHORE-GRASS. 



23. A&I8TIDA L. Tufted plants with contracted or open panicles, uhi.-h 

 are sometimes nearly racemose. Spikelets narrow. Scales 3, the outer 2 mem- 

 branous, the third scale narrow, rigid, strongly convolute, often with a promi- 

 nent callus at the base, the generally spreading awns glabrous to plumose. 

 POVERTY -GRASS or WIRE GRASS. 



Leaf blades flat, not vlHoim nt the hnxe. 



Pint umlp of the Hiilk.-li-t untidily shorter than the second: flowering scale less 

 than 8.5 mm. long. 1. A.Chapmaniana. 



Firm scale of the uplkelet usually longer than tbe 



second: flowering scale over 5.5 long. 2. A. purpurairmt. 



Leaf blades Involute, st least those of tbe 



of tbe lower ones and 

 vlll 



those of the Innovations, densely vllloos. 8. A.lri>t<i. 



